Seasonal Changes in Florida Grapefruitageconsearch.umn.edu/bitstream/169863/2/tb886.pdfTechnical Bulletin No. 886 • April1945 I Seasonal Changes In Florida Grapefruie By P A:UL L.

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MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS·1963·A

Technical Bulletin No. 886 • April1945

I Seasonal Changes In Florida Grapefruie

By PA:UL L. HARDING, horticulturist, and D. F. FISHER, principal horticulturist,Division of Fruit and 'Vegetable Crops and Diseases, Bureau of Plant Industry, Ii

Soils, and Agricultural Engineering, Agricultural Research Admim'stralion 2

CONTENTS Page

Factors influencing Quality of commercialgrapefruit•••....••.•.....•.••.••...•.....•. "\nlllyscs of chemicnl constituents.............

Page 24

Definit.ions of maturity and ripcncss...•.•... 1 Ascorbic acid...... ..... ...••.••••.••..... 244 'fotal ash .•..•...•..• '" ..•.•••.••...•••.••Rcl~tion of findings to maturity laws ....•..•. 25l\Iat.crial, methodS, anel rcllltcd information .. .5 Constitucnts of ash. .••••..•.••..••..••.•• 2611 pectic constituents. .•....•.•••..••..•.••• 28Expcrimcntal proccdures.............. '" 11Factors influencing quality and the

Active acidity, or pn \'filucs.............. 28Heducing sugars, sucrose, and totalmcthod of cvalullting plllatability..... .. 14 29M.ethotls for a "eraging ccrtain physical 'r~~.fr~~iidi::=====::::::::::::::::::::::charactcrs and ehemic:!1 constituents... 10 'I'otal acid •.•••••••••...............•.•••.• 31Interrclation of soil, rootstock, and qUlllity. 3tClimatological i:,formation in rclation to Ii Hatio of total solids to total acid.••..•.•.. 34seasonal \'nrint.ioll~~ .. _ ... ~_._ .. ~.~~_~_ .. _. Relation of arsenicnl spray law to grapcfruit.. 35IS ElTects of leael arsenate spray....••...•••.•••. 44Analyses of ,'arious physical characters••..••. I!) '''eight of fruiL ..........................Color of rind............................ . 19 44Volume of juice.......................... 44Weight of fruit. .•.••.••.•••.•...•.•••..•. 20 Ascorbic acid......... . •.....•••.••.•.•. 44Diameter of lruit .•.•...•....•••.•..•.•.•. 20Thickness of rind.....•••...••.•..•..•..•. 20 'rotal solifarianFloyd, 1\frs. Varina L. Frceman, Fronds Inglc)', Mar)' Janu Kirst, O. B. Kni~ht, G. A. 1\{eckstroth,Hobert Rechl, G. Lce Hoherts, 1\r. Bryan Sun!lay; Edward Thomas. and Mrs. Franecs Whitley; theassistance of othcr staer membcrs of the Unitcd Stlltcs Dcpartmcnt of Agriculture who regularly partic·ipateel as tnste judges is also ncknowl('(lg~d.

3 WILLSON, n. F. lIAU!rETI1W ,'LOIIIDA CITRUS: SUlUIARY OF 1041-42 SEASON.Market Bur., 82 pp. 1942. [Processed.] (Sec pp. 79-82.) Fla. Dept. Agr. State

617886°-45--1 1

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'PECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE2

54 percent of them; according to market reports 35 percent of the

Florida fruit is from seedless varieties. The average gross return for

the Florida crop from 1932-33 to 1941-42 was $15,477,244, the

lowest being $12,289,942 in 1939-40 and the highest $22,849,773 in

1941-42.-1Correlating the internal quality of grapefruit with its physical

characters and its chemical constituents as they chnnge during the'

shipping season gives a better idea of the characteristics of the fruit

that enters commerce; such correlation should enable growers to fore

cast with a reas'onablc degree of assurance the probable quality of the

fruit on any particular date. Only if fruit is harvested wli('n high palat

ability is assured, can shipping space be utilized most effectively and

unfavorable consumer reactions be avoided. The benefits from propel'

hs:'Vest dates are particularly important when food conservation is •essential and transportation facilities are congested.

The information presented in this bulletin on the physical charncters

and the chemical constituents of sprayed and unsprayed Florida grape

fruit during the four seasons, or crop years, from 1939 to 1943, on the

changes 01at occurred in the fruits as they matured and ripened, and

on the factors tlULt influenced eating quality and food value, should

sen"e as a basis for improving maturity standards and for establishing

legal picking dates for both seedy and seedless varieties. Heretofore

varieties have not been differentiated in considering maturity

standards or in choosing harvest periods. The summary of the results of studies presented in this bulletin is

based on the periodic analysis of more than 15,000 individunl fruits and

more than 1,000 composite samples of 25 to 50 fruits each. The prin

cipal varieties studied were the seedy Duncan 5 and the seedless 1faJ'sh;

the pink-fleshed, seedy Foster and the pink-fleshed, seedless Thompson

also were llsed in some of the tests. These varieties were budded on

rough lemon or sour orange rootstock and were grown on soils of vari

ous types. Both unsprayed fruits and those sprayed with lead arsenate

according to commercial praetice were analyzed. Degreening of the rind was found to be associated with the ripening

of the fruit on the tTee. By Jal).ua1'y or February practically aU the

green had disapprared and the characteristic yellow had developed.

The a,vemge weight of the fruit increased with maturity, but the

Duncan fruit was l1ea\rler than that of the :Marsh. Increase in size,

represented by changes in the diameter, also was associated with the

development of the fruit, but the rate of size increase decreased as the

frui t ripened.The fruit had slightly thicker rind when the trees were on rough

lemon rootstock, ('specially on light, sandy soils. Immature grapefruit had ricey-textured flesh and that picked be

tween Noyember and January was usually coarse; that picked after

January or February, 11ow('ve1', had good texture. Changes in the

color of the flesh were usually associated with changes in texturr, the

good-textured fruits having a deeper yellow or tannish-yellow flesh

color. , SCRUGGS, F. R. A~~UAL FRUIT AND Y.:GETAULE REPORT: 1941-42 SEASON.

Flu. Dept. A~r. Stnte l\[nr·

ket Bur., 83 IlP. 1942. [Proeesscd.] (Sec p. 9.) , III this bulletin the terms" DUllcan" and "Dunclln ,·aril't.h's" refer to a typ

e of seedy grnlwfruit usulllly

n~fcrred to in commerce lIS "Florida Common." It is possillle thut most of the ~ro"es producing this typo

of fruit mll~' own their origin directly or indin'etly to tho pllrent Duncan tree. Citrieultnrists generally arc

ofthuopinion, howcwr, that they clime from dilTcrl'nt sourees of old, noteworthy seedling trees. 'l'he Duncan

type fruits and trees haye so rnllny points in cornlllon tlull, in most cases ilitTercntiation is impossible. 'l'he

historiy of lIluny of tllU groves is 50 obscure that the source of the bu

SEASONAL CHANqES IN FLORIDA GRAPEFRUIT 3 The volume of juice, computed as milliliters of juice per 100 gm. offruit, increased with development until the fruit was ripe, when it remained rather constant. Varieties differed in juice content. Probably because of its practically seedless character, the Marsh consistently had a slightly greater amount of juice than the Duncan.In immature fruit there was no significant difference in flavor (taste)among the several varieties regardless of the rootstock. Rootstockdid, however, affect the quality of the ripened fruit; fruit on sourorange stock was superior in flavor to that on rough lemon. Furthermore, although the varieties Marsh and Duncan were about equal inqUtllity when on sour orange, the Duncan was rated superior to theNlarsh when they werc on rough lemon.There was a gradual lowering of conccntration of ascorbic acid in thefruit as it matured and ripened, but the to'/.;al ascorbic acid per fruit

" tended to increasc as the volume of the juice increased with advancing maturity.The total ash content of grapefruit jUlce was generally highest inimmature fruit; it gradually decreased as maturity progressed, although very ripe fruit picked in April showed a slight increase.Analyses of the ash of the flesh showed a greater content of potassiumin the Duncan than in the :Marsh fruit. Analyses also showed agreater content of calcium and magnesium and in some cases of pot3ssium in fruit picked in November, as it approached leg!!l maturity,than in that picked in May, whcn it was very ripe; generally, however,the greatcst amoun ts of manganese werc found in very ripe fruit pickedin l\lay. The content of iron varied considerably but showed no definite trend. However, the variations among groves and picking periodsare such that the small differences found between varieties and rootstocks are of doubtful nutritive or statistical significance.Pectic constituents generally decreased with the ripening of thefruit, protopectin being more consistent than soluble pectin in thisrespect. The middle-lamella pectin was erratic, but it had a tendencyto decrease as the fruit ripened.During the commercial shipping season the acidity of the juiQe decreased gradually with ripening. In very ripe fruit picked in Apriland May the acidity decreased abruptly.Reducing sugars increased with the ripening of the fruit. Silcroseusually increased during the fall month!:., remained rather constantduring midseason, and decrellsed sharply between February and April.Total sugars increased during the fall and midseason and usually remained constant in ripe fruit.

. Total solids, or total soluble solids, (principally sugars) were generaUy highest when the grapefruit was in prime eating condition.Slightly lower total solids were usually found earlier in the season inimma.ture fruit and also late in the season in very ripe fruit. :Marshand Duncan fruit on sour orange rootstock contained a greater amountof total solids than did that on Tough lemon. Comparisons betweenvarieties on the saIlle kind of rootstock showed that the Duncan contained higher total solids than the Marsh.A. downward trend in total acid characterized both Marsh andDuncan as they ripened, but the Duncan was consistently higher intotal acid than the 1\Jarsh. Although total acid was influenced moreby variety than by rootstoek, the fruit on sour orange rootstock wasl'n.ther consistently higher in total acid than that on rough lemon.

4 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE

The solids-k~acid ratio generally increased with the ripening of the fruit. This increa,se was primarily due to a diminution in the total acid of the fruit, since the total solids remained rather constant in ripe fruit.

Spraying the trees and fruit in Ju1y with one applica.tion of lead arsenate (at the rate of 1 pound of lead arsenate to 100 gallons of -water), the practice commonly followed commercially, brought about a significant reduction in total acid. The total acid of immature sprayed fruit was about 4 to 9 percent below that of the unsprayed, and that of very ripe sprayed fruit was as much as 21 to 26 percen t less. The lowering of the acidity by spraying with lead al'senate resulted iu higher ratios of total solids to total acid; this, in turn, resulted in earlier maturity, as judged by present legal standards, and more palatable fruit, as shown by the higher average numerical taste ratings. On the other hand, spra,ying resulted in a slight decrease in the weight of the fruit and consequently in its size. It did not, however, significantly lower the volume of juice computed on a percentage basis or as milliliters of juice pel' 100 gm. of fruit, or affect the concentration of ascol'bic acid or tbe total solids.

DEFINITIONS OF MATURITY AND RIPENESS

Throughout this bulletin reference will be found to maturity standards, which are legal requirements established by State l.ows and enforced by State and Federal regulatory agencies. In this study the characteristics of the principal varieties of grapefruit have been 1'0.la.ted to the legal maturity standards at different times prior to a.nd throughout the normal harvesting period.

To avoid possible confusion in, or misconception of, the meaning of the terms "maturity" and "ripening" as they are used in this publicationtheir common hortic-ultural meanings are defined. Maturity refers to a stage of development of a fruit; rip('ning, to the process by which a. mature fruit when held under suitable conditions becomes edible. A mature fruit is one that has attained such a stage of development that it will ripen with acceptable eat~ng quality. Fruits with starchy reserves, such as apples and pears, may be mature at harvesttime, but, they may not ripen or become edible until sometime thereafter, when they attain their soft, juicy, aromatic qualities. Grapefruit and oranges are dift'ereut from apples and pears in this respect; they contain practically no starch and do not undergo such a rom'ked change in composition after being severed from the tree. Since the ripening processes of citrus fruits can OCClir only while they are attached to the tree, it is obvious that they should not be harvested until they are mature and hence ripe. Instead of incrcasing in quality after harvest, grapefruit and oranges tend to lose quality, the rate of this loss being correlated with the temperature at which the fruit is held.

It is important to keep in mind, therefore, that grapefruit must be of desirable eating quality at, the time of harvest in order to be regarded us mature. On this basis, then, gru.pefruit must always be tree-ripened. The importance of maturity of gru.p('fruit and of the 1('gal definition of maturity as established in different producing sections, therefor(', becomes appu]'Put. The present study was designed to show thc seasonal behavior of the principal varieties of grapefruit; for the purpose of comparison the relation is shown

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SEASONAL CHANGES IN FLORIDA GRAPEFRUIT 5 between this behavior and the legal maturity standards in effect whenthis investigation was conduded.

RELATION OF FINDINGS TO MATURITY LAWS Ramsey (26) 6 stated that appearance alone, involving texture,color, and scars, is important, but in the final analysis satisfactoryeating quality and juice content arc {)f greater importance in givingconsumer satisfaction. Fabian and Blum (9) reiterated the samepoint of view in saying' that flavor is one of the mQst important attributes of any food produced for human consumption. No matter howattractive the food may be in appearance, how e..xpensively it may bepackaged, or how nutritious it is, future sales will be negligible if itdoes not suit the taste of the consumer. Provan (25) stated thatimmature grapefruit which possesses a sharp and raw bitterness willnever be popular with the iVfelbourne, Australia, public. Acidity,the Brix test, or the solids-to-acid ratio did not fully indicate a suitableperiod of maturity, but the palate test showed that grapefruit haddeveloped full flavor and could be considered mature after July 1 inAustralia.The results presented in this bulletin indicate a very close correlationbetween the flavor of grnpdruit, as determined by taste, and theseasonal changes in the weight and texture of the fruit, the color ofits flesh, the milliliters of juice' per 100 gm. of fruit, and the ratio oftotal solids to total acid. These increased with the matlll'ity and theripening of the grapefruit on the tree, the trends of change duringthe season being rather similar in the different lots. By recordingthe picking dates and plotting the total solids and total acid in nomograph form, it was possible to show the relation of these factors toeach other in fruit at its earliest stage of accf'ptnbiiity, as judged byits flavor, and eventually to determine a minimum standard of acceptability for the different varieties.The flavor of the grapefruit used in this study began to meet consumer approval as follows: :Marsh on rough lemon rootstock from aboutDecember 1 to January 22 (fig. 1, A); Nfarsh on sour orange, fromabout October 20 to January 1 (fig. 1, B); Duncan on rough lemon,from about November 15 to January 3 (fig. 1, 0); and Duncan onsour orange, from about November 1 to January 1 (fig. I, D). Therewas a· marked seasonal variation, also, in the maturity dates; grapefruitmatured earliest during 1939-40 and latest during 1942-43.The interrelation of the means of physical characters and chemicalconstituents of jyIarsh and Duncan grapefruit for the four seasons arepresented in figure 2. They show that according to flavor ratingsDuncan grapefruit began to meet consumer approval about. December1 to 20 and Marsh about December 1 to January 1. These findingsare in agreement with the popular local opinion in Florida, wheregra pefruit is generally regarded as too tart for eating before Christmas.The fruit of both the ~IIarsh and the Duncan variety became moreacceptable in quality earlier in the season when the trees were sprayedwith lead arsenate than wben they were not sprayed with it. Thisearlier maturity appears to be due primarily to a lowering of the totalacid content of the fruit as a result of some. obscure physiologicalprocess induced by the application of the arsenicaL The comparative

, rtnlic numbers in parentheses refer to Literature Cited, p. 47.

6

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TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE

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--- 1939-1943

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AUG, 25-SEPT,2

SEPT. 25-30

OCT, 23-28

NOV, 20-25

DEC, 18-23

JAN. 15-20

FEB. 12-17

MAR. 11-16

APR. 6-13

MAY 6-11

PICKING PERIOD

FIGURE l.-Seasol)al changcs in average numcrical ratings of grapefruit flavor, 1939-43: A, Man;h 011 rough lemoll rootstock; B, 'Marsh Oil sour orange; C, DUllcan on rough lemoll; D, Duncan ort sour omnge.

7 SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

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8 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICUVfURE

'.., composition of sprayed and unsprayed fruit is shown in tables 34 to 60, Appendix.

In Marsh grapefruit rated as pleasantly tart in flavor (fig. 3) the total solids ranged from 7.37 to 12.53 percent and the total acid from 0.97 to 1.67 percent. In pleasantly tart Duncan. gmpefruit (fig. 4) the total solids ranged from 8.37 to 14.39 and the tot.al acid from 1.07 to 2.38 percent, respectively. In other instances there was a greater range in total solids and total acid in acceptable Duncan fruit than in acceptable Marsh fruit, particularly in total acid.

The difl'erel1ces between acceptable Marsh and Duncan fruit are brought out plainly by superimposing the nomograph for Marsh (fig. 3) on that for DUilcan (£6' 4). It can be readily seen that the two nomographs do not fit particularly well, because the acceptable l\'iarsh fruit generally had a lower content of total solids and a lower and smalier l'fiIlge of total acid than the Duncan fruit. These charac

'I-.~19.00r----------_______________---; 0.90

18.00 1.00-- ROUGH LEMON ROOTSTOCK -- - - SOUR ORANGE ROOTSTOCK

17.00 1.10

16.00 1.20

;: 15.00 1.30~ z Iw z ~ 14.00 1.40~ w cr !:: 13.00

9 SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

It should be kept in mind that the physical and chemical changes occurring during the ripening of grapefruit are very gradual. In dealing with such data the use of nomogruphs, such as those presented, offers a practical way of correlating difi'erent factors and obtaining a better working basis for maturity laws and internal fruit grades. It is not likely, however, that these alone would prove wholly satisfactory unless supplemented by picking dates that are logically selected and legally established.

A maturity standard based on these findings would undoubtedly defer the shipment of some early grapefruit legally mature under the present law. On the other hand, it would make possible the earlier canning and shipment of acceptable grapefruit of certain varieties that arc characteristically high in total solids and total acid. Actually such fruit is highly palatable, but under the present laws it is rated

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-- ROUGH LEMON ROOTSTOCK

---- SOUR ORANGE ROOTSTOCK

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FIGUHE 4.-Komograph sho\Ying the contents of total solids and total acid in Duncan grapefruit when first rated as meetillg consumer approval according to the taste test. These data were obtained during four seasons (1939-43) and included tests on fruit on rough lemon and SOIir orange rootstocks as well as on that from trees sprayed with lead arsenate. ·tIeayy linc indicates minimum total solids and maximum total acid of acceptE.ble grapefruit.

technically as immature becallse of low rntios. During the past few seasons much of this high-quality fruit hus been encountered and, in accordance with legal requirements, has been discriminuted against.

In considering grapefruit maturity, v,u·ietnl churncteristics apparently have not been emphasized in the past becnuse all varieties of grapefruit are subject to the same maturity la.ws. In Florida, these laws are based largely on three components (color of rind, chemical composition, n.nd volume of juice) a.nd ,1.1·e briefly cited as follows from the Citrus Fruit Laws, August 1941 (10,1).38):

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10 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE

Section 3. That within the purpose and meaning of this Act, grapefruit shall be

deemed to be mature only when clipped or picked, or otherwise severed from the

tree each grapefruit shows a break in color caused solely by nature, and when the

total soluble solids of the juice thereof is not less than seven (7%) percent, and

when the ratio of total soluble solids of the juice thereof to the anhydrous citric

acid is as sct forth in 8ubscci;ion (a) of this Section, and when the juice content of

said grapefruit is not less than the minimum requireHlent for the respecth'e sizes

of said grapefruit as set forth hereinafter in subsection (b) of this Section.

When the total soluble solids referred to in subseetion (a) of this

section range from 7 to 9 percent, the minimum total soluble solids

acid ratio is 7 to 1; when the runge of total soluble solids is from 9.1

to 9.9 percent the ratio is graduated, the minimuOll'atio being 6.50 to].

In Texas, the ratio requirements for grapefruit are very similar to

those in Florida and range from 6.5 to 1 to 7.2 to 1; however, the total

soluble solids take in a range of ft'om 9 percent to 11.5 percent. Sec

tion 3 (28, p. 132) of the Texas maturity la'\\' is quoted as follows:

Section 3. That, within the purpose and meaning of this Act, pomelos (grape

fruit) shall be deemed to be maLure only whell the ratio of total solublc solids of

the juicc thereof to anhydrous citric acid is as follows:

(a) When the total Bolub!;"· solids of the juice is not less than nine percent (9%),

the minimum ratio of total soluble solids to the anhydrous eitric acid shall be

seven and two-tenths to one (7.2-]).

(b) When the total soluble solids of the juice is not less than ten percent (10%),

the minimum ratio of thc total solublc solids to tilC anhydrous citric acid shall be

scven to one (7-]).

(c) When the total ~oluble solids of the juice is not less than eleven percen t

(11 %), the minimum ratio of total soluble solids to the anhydrous citric acid shall

be six and eight-tenths to one (6.8-1).

(d) When the total soluble solidH of the juice is not leRs than eleven and onc

half percent (11.5%), the minimulll ratio of the total soluble solids to the anhy

drous citric acid shall be six and one-half to one (6.5-1).

In Arizona (1, pp. 22-23), the minimum ratio of total soluble solids

to acidity is 6 to l. In California (4), dual ratio requirements prevail,

depending on the section where the fruit is grown and the minima are

5.5 to 1 and 6 to l. The reason for this dual standard is the difference in climatic conditions prevailing south and east of San Gorgonio Pass, which results in the grapefruit grown in tIllS area having at maturity a higher percentage of soluble solids to acid than that grown in the area north and west of San Gorgonio Pass.

In Texas, Wood and Reed (33) found that grapefruit from widely separated orchards on different soil types and under different soil management matured at approximately the same time. The various cultural practices exerted more influence on the physical characteristics than on the chemical composition of the fruit. They stated that the totll1 soluble solids contcmt and the solids to acid ratio, in conjunction with a specified minimum juice content, appeared to be the most practical and the best measures for determining the maturity of grapefruit. In Arizona, Hilgeman and Smi tIt (16) and Hilgeman, Van Hom, and Martin (17) found that the exact point at which a grapefruit may be considered edible presented many difficulties and that no consistent differences in maturity as ilJ(Iicated by the ratio of the total solids to acid were noted in fruit from various fertilizer plots, but that marked • seasonal differences were obJerved. Hilgeman (15) advised that no fixed standard be adopted and suggested that an authority be established and empowered to set standards for each season as might be deemed advisable, to prevent the shipment of lUlpalatable fruit.

Baier (3) conducted maturity studies on :Marsh grapefruit grown in

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT 11

California, and Arizona. He pointed out that it became evident during the course of the investigation that Marsh grapefruit from different sections varied considerably in characteristics when it passed the fundament/al tests of maturity. Thus came t0e suggestion for the socn.lled dual standn.rd, for some years n. part of the California Fruit, Nut, and Vegetn.ble Standardization Act.

MATERIAL, METHODS, AND RELATED INFORMATION

EXPERIMENTAL PROCEDURES

The present investigation covered 4 seasons, 1939-40, 1940-41, 1941-42, and 1942-43. AlloJyses were made mostly Oll the Marsh and Duncan varieties of grapef.ruit, since these are the principal ones gJ'Own in Florida. In addition, however, analyse" were made on the Foster variety dUJ"ing 1939-40 and 1940-41 and on the Thompson during 1941-42 and 1942-43. Analyses were ma.de periodically on the fruit from 10 different groves of :Marsh grapefruit on rough lemon rootstock, from 6 of :Marsh on sour orange, from 8 of Dlllcan on rough lemon, f\,nd from 6 of Duncan on sour orange.

In addition extensive tests were ·inade to determine the effects of lead arsenate spray on the composition and quality of J\:Iarsh and Duncan grtlpefmit. Tests werl' mn.de on the fruit from 27 different plots of tl'eps sprayed\with lead n.rsenttte and on that from 28 compflrable unspmyed plots. Spray was applied in July, many weeks prier to commercial harvest, generally at the mte of 1 pound of lead arsenate to 100 gaJlons of ,,"ater. The tests on the fruit were started 11bout the last of August and continued until the middle of 1 ilay of NlCh season; therefore, the analyses included fruit in various stages of maturity anciripening,

In making the seieetion for the e:qwrimental plots in commercial groves a definite plan was followed: Plots were chosen in the ridge district, where the soils are usually low in organic matter (pI. 1); in tIl(' east and west coast districts, where the soils haye a higher organic matter content (pI. 2); and in the Homesten,d district, where the soils are very rocky (pI. 3). Pertinent information 011 the soils and locations of the experimental plots is given in table 1, and the soils are d('scribed bridly on pages 17 and 18.

In each of these districts the ,plots were made up of 11arsh and Duncan varieties on rough lemon and sour orange rootstocks. Other plots were added to supplement the filldings, These were selected on the basis of the predominating variety 01' rootstock found ill the particular district. For example, if the ~Jursh 011 rough lemon rootstock was most common, 1110re of such plots were chosen in all attempt to make the investigation representative of existing conditions. In lh('se groves plots of 15 to 25 tr('es eHch w('re selected. In the choice of both groves and plots care was taken to a,void abnormal cultural and fertilizer practices, and complete records relating to them were obtained each season. Since this study was undertaken for the purpose of obtnining an oyer-all picture of grapefruit and the quality that might b(' expected on the market I1t clill"el'ent times, it is not deemed necessary to set forth in detail the production practices followed in ('l1ch grove. The groves were in good avemge condition and hacl been supplied with ample amounts of primary nnd secondary nutritive (11(1111ents. Very young nnd vcry old tr'pes. and those producing very

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12 TECHNICAL BULLETIN 8!16, U. S. DEPT. OF AGRICULTURE

TABLE 1.-Varieties of grapefruit, rootslocks on which they were grown, soils, and local'ions of experimental plots in Florida, 1939-43

Variety Rootstock I Age of I Season of invest/· trees 1 Soil gationf , IYears

Marsh•••••..•• Rough lemon ..

Do•• __ .... SOllr orange

Duncnn .•__ ... Rongh lemOlL.

Foster (pinkl- ,.. do

Thompson /.. do. (pink).

18_. ..••.• Davenport. ,. Norfolk sand .......... .

26•...•.• , Lnke IJnmil· .....do................_.

ton.

15.. , •••.. Windermere.. Norfolk fine sand ...... . 15...._. .. Minneoln.........do ............... 15....... . Hn'i~rln'rhe Blnnton fine sand .... . 22•.•.•.•. Bradenton.... Bradenton fine snndy

lonm.' 20..... , •. Clenrwater•.•. Norfolk line snn(L. ' •. 15._ """ Fort Pierce.... Bradenton line snndy

loam.' About 27" Homesten(L .. Rockdale rockland,

cluyey phase. 2·J ...........do........ . Rockdale rockland,

sandy phase.20. Dn\·enporl... . Norfolk slln(1..

About 22 Brndenton... . Bradenton fine sand)'101lm.'

16..... VeroBeach .•• Manatee fine snnd~' loam.'

19 ...... ' .••do" •. Felda loamy fine sand '.25 _ _, ~ _~ Fort l)j('l'cc. Blnden fine sandy loam 2·L. ...... IJomcslelld.. Rockdnle rocklllnd,

snndy phase.18 Dnvenport. Norfolk sand .......... .

26. Lake Hamil· .....do.. ,,_. ........... .

tOil.

20...• _.. Jlfinncoln •. Norfolk fine sand .....

24 ........ Palmetto Bradenton loamy fine

sand.' 20 ... ". Clcarwater.•.. Norfolk fine snnd

28............do... " ... . Blnllton fine snnd .... '

15. .... Fort Pierce •••• Bradenton fine snndy

IOllm.3 About 27 Homestead Rockdale rockland,

clnyey phase. 20 ... Dnvenport .. Norfolk sllnd .....

About 30. Dundee. . ".do......... " .. ..

31. Palmctto.. Bmdenton fine sandy

lonm.' < ...22. Vero Beach .•. Manntee fine saudy

loam.' 15.. ,do...... P"rkwood fine sandy

loam.19. __ ... do .. " ... . Felda loamy fine snnd',25 Fort Pierce.. .. B1nrlen fine sandy loam. 10.... Brildonton .•.. Bradenton lIne sllndy

lonm.3 Bradenton loamy fine

snnd.'

1939-10, 1940-41,

1041-42,' 1942-43.'

1940-41, 19·11-42,

I!H2-43.'

1039-40,' J!J.lO--I1.' 1942-43.' 1942-43.'

1939-40, l!J.l0-41, 1941-42, 1942-43.'

1042-43.'

1939-40, 1040-41,

1941-12, 1942-43.'

1039-40, I!J.lO-Il,

10-11-42.

1941-42.

1039-40, 1949-11,

1941-12.

!O39-40, h)40-4 1,

1041-42, 1042-43.'

1939-40, 1040-41,

1941-12, 1!J.l2-43.'

1942-13.' 1942-13.' 10H-I2.

1939-10, 1949-11,

19,11-42,' 1042-43.'

1!J.l0-41, 1941-42,

1042-13.'

1942-13.' 1939-40, 1!J.l0-41,

1041-42, 19·12-43.2

1942-43.'

1!J.l 2-13.'

1930-10, 1!J.l0-41,

10-11-12, 1042-43.'

1939-10, 1!J.l0-4I,

1941-42.

19:1!I-IO, 1940-41,

1041-12 .

1042-13.'

1939-10, 1!J.l0-4I,

1941-42, 1942-43.'

1942-13.'

10:19-40, 1940-41,

1041-12,1942-13 •

1942-13,2

1942-13.'

1939-40, 1940-41.

1941-42, 1942-13.

I Age of trees lit the time the experiment wns started.

2 Plots spmyed with lead arsennte eompareti with eontrol plots.

''l'entath'e name of soillllapped In :l!'loridn but 110t. yct correlated.

light crops of fruit were not used. Care was always exrl'cised to piek only fruits from the regular bloom; otherwise, the grapefruits for all the tests WCI'C selected at random.

The fruit samples were takcn to the laboratory at Orlando, Fla.,

immediately after they were picked and were placed ill storage at

32° F. until tested. Each sample consisted of 60 or more grfipefruits

picked at random from the 15 to 25 trees. During the 3 seasons from

1939-1942, 25 fruits were fil1alyzed individually. These individual

analyses brought out the variation among the fruits and the percent

ages in each sample which passed 01' failed to pass existjng legalre

quirements for .total solids and acid. The remaining fruits were used

Technical Bull

Technical Bulletin 886. U. S. Department or Agriculture PLATE 3

Rockdale rocklalld Ruil ill tll(! 1I0lllPRfl'ad diRtTic(- fairl\' wnll Rllitcr! to citTIIl'. It diffC'rll from 1l1()~1; eit rUR :;oils ill Floridil. Bt'forc it is plnllt(!d to cit rlls I-u·ovp>;, til(' virgin Roil requires Uiorollgh sCllrification ill orcic'r to brl'nk up t lIP :mrfacl' rock cru:-;t; in add ilion, holns un' wHluily hhu;t I'd for ('tlell t.ree.

13 SEASONAL CHANGER TN FLORIDA CIlAPFWHUl'l'

for taste tests (fig. 5) and for ascorbic acid ddenninations. For the latter determinations the juice WitS ('ximctecL from the grapefruit by hand squeezing and then straiut'{l through cheeseeioth in order to remove the serds and pulp. Aliquots of this composited juice were used in the ddermination of ascorbic acid. During 1942-43 all the tests were made on composited juice samples nfter the seeds and pulp had bern sl'}Jal'ULl'c\ from thl' juice.

8amp1('s Wl'I'(, col\rcted from all th(' grov(,s at 4-\\'cck intervals. T('sts W(,l"l' stnrtrd ilbou t the last of August on immil ture fruit and continued through pach s('ason until nbout th(' middlp of nIuy, ",lI('n lllP fruit wns\'('ry rip(' 01' overripe, as shown by th(' pn'senc(' of sprouting set,cls, grnllulation, nnd off-f1u\'ors. This long lWl'iod of snmpJing pI'ovitil'(1 information on th(' changrs in physictll ehul't1.ctcrs and cll('miC'ul eonstiluents of thr fruit duriug the various stages of mutlll'ity and ripruing. (8('(' tfibh's 1:3 to GO, Apprudix.)

F~GrRE 5.-Sample;; of grapefruit arranged 011 a laboratory table for tltWor, or ta;;tr, ('valuation. Each judge wm.; acl\'iscd to tafit(' "p"eral pipccs bcfor(' rating a samplp nc('ordilll! to th

14 TECHNICAL BULLETTN SSG, U. S. DEPT. OF AORTCULTURE

Official methods were follow('d in determining the chemical constituents (2).

FACTOHS IXFLUENCING QUALITY AND THE :METHOD OF

EVALCATING PALATABILITY

The internal quality of grapefruit is influenced b.'T sewrnl fnctors such as acidity, sugar eon tent, ratio of totnl solids to totnl fI('id, j uici-

FIGUHE G.-Hand press used for extracting juices during J939-40.

nes~, textur~ of flesh, and aromatic condtituents. TIl(' age of the fruit is also important. ImmnturC' gmpdruit is usually very acid or tart and hns a rnw und immnture tnstl' , whereas overripe fruit held on the tree too long nnd tiw,t sprn.yC'd with higb concentrations of lead arsenate may become insipid or devdop disngreenble off-flavors. No onc relishes immature, very fieid, ric('y fmit. TherC' also appears to bl' a

SEASON AL CHANGES IN FLORIDA GRAPEFRUIT 15

prejudice against vel'y insipid fruit or that in which the seeds have sprouted. Individuals differ in their preference for degrees of tartness and sweetness; some customarily ndd sugar and others use salt on grapefruit, but many prefer no added flavoring.

Throughout this investigation assays for flavor or taste were made on the fruit to which no sugar or salt had been added. In each test 30 to 50 grapefruits were used. The fruits werr cut in half transversely, and from each half was cut a wedge··shapec\ piece for tasting (fig. 5).

Staff membprs of the BUl'etLU of Plant Industry, Soils, a,nd Agricultural Engineering and of the Bureau of Entomology and Plant Quat'11Iltine statio))('d nt Or1ando I'pgularly officiatpd as tastp judges, Frequently visitors also WNO present, and they too w('I'e iuyited to score the various samples, 11]'om] 5 to 28 tast!' judges appra.ised and scored

FIGU.RE 7,~Electric reamer used for extracting juices during 1940-41, 1941-42, and 1942-43.

ea('h lot of fl'lliL, ~Uld the l1ul11Nieal1'lltings werc avemged. Scoring of all samples of grapefruit wns done aecording to the arbitrary standard scale ~hown 011 pngp 16.

At the beginning of ench season, the arhitrary standard scale to be used and the method of pyaluating the internal quality of grapefruit were discussed with the stafr l1wmbers who were to participate as tnste judges. At thn,t time it was brought out tlwt illP 1l11mcl'ical value of 70 \"olIld be til!' millimum stnndfll'd of acceptability :llld that any grappfl'uit rated Iwlow thn.l vnJut' would be eonsidl'l'ed undesirable. On the other hand, de~imb}P intCl'l1al qunJily was given values of 70 to 100 as indicaled.

An effort has been made to COl'l'eiate the internal quality of grapefruit, as determined by taste, with the total solids tmd the tolal acid

16 TECHNICAL BULLETIN 886, U. S. DEP'l'. OF AGRICULTURE

SCORE CARD FOR TESTING TASTE OR FLAVOR OF GRAPEFRUIT

1Numf'ricnl i fndi. I 1 mting ~ \'idunl Afbltfan.. standard I '1'as!" Of flomf of ffuit r~~rl~~~~;?I~:r ~ uumer

~ ira!. to (tf~~fiJl'; rating! ----- .__ .__.._-------_. ---~

Very acid~ ~ _~ .... _ ~ _.1 "'cry acid. rn\\", immntllrr f}tn"or . _... 20-:lU A cid __ ~ ~_~ .... _.... ~ _.. ~ 1 ,,:\cid with tlllSt'IW(\ of raw, immnture fln \'or ~ ~ __ ~ __ ~ _.~ 40-50 '1'aft........... . •. : Too lnrLfof "onSllrnrf appfornl. •. '" " .. _.. __ ••••• OO-fiO .Pleasantly taft . .: :'Ilinimtlrn Sla~(, of accl'plnbilily for conSllnWf. .•.•.. : iO-ill Plcasnntl~' tort to i Plcnsllllt hlrnd of sllgnfs anel neid, with \"l'fl' ~ood tr'xlur~ 80-100

SWl'l,t~ i nnd 1111\'or. , lnsipid (nged) ~".,.! Yery SWl1IIC wnh'r~·, In(lkin~ in no\"Of, low in nddit~"', ngc(L __ : 50-100 , ______ 1.•___.•.. .____._~_ :

('ont('nt of tIl(' fruit. Thi~ \ViiS n('complish('d by tabulating.thc percrntages of totnl solids and tolnl neid of n11 snmples of grapefruit at th(' tim(' t1H'Y \\'('1'(' first e1nssified as TI1(, ('ollsid('l'('d of pnlaln.ble eating qun.lity. It is nlso in\.('I,('~ting to 110tl' that usually W}ll'll nn a('('('ptablt, grllpdl'uil had n low totnl solids coni.I'IIi it. nl~o had n. low acidity, nnd n fruit with high 01' V(,I'Y high total solids ('ont('nt nlso had high acidity. An t'xHmpl(' of til(' Inll!'I' is shown ill figUl'(' 4, ",hith iudicn\.('s that Duncan fruit ",us accl'plnble whl'll the acidity "'flS 2.:38 percent. Ordinarily this fruit would be cOllsitierwL far too Heid, but tIl(' uccompnllying lotnl solids ('onl!'lIt of OYP!' 14 percent dcmon~tmt('d that tastl' ",us infiuellced hy Ih!' ratio of solids to add in this fruit.

METHons FOil AVEHAGING CEHTAIN PIIYSIC.\I, CIIAHACTEHS AND CIIE~lrCAL CONSTITUENTS

COLon OF UlJIm,- Thc' color of Ihc' rind of ('nell in

17 SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

designation: Ricey, coarse, anti good. The average texture of the flesh for eaeh sfilnpk WI1S ascC'rtuinC'd by assigning a numerical value to each t('xture d('signn.tion und av('rnging these values (fig. 2); or each I1vcrngt' wus cOl1vn-ted to the neUfest texture designation, as shown in tnbks 13 to GO, Appendix. AYERAGJ~ pH VAr.rEs.-The ayerage pH vDlue wus detC'rmined by

av('rn~ing tIl(' antilogs of the pH \-ulul's nne! rOI1\-('rting til(' an'ruge antilog h:1('k to the pH \-n,lue (fig. 12).

l:\TEHHET~ATJ():-; OF SOIL, HOOTSTOCK. A)l1) Ql'AUTY 7

A hrief d('scription of soml' of the soils plantNf to rib'us is gi,-en he]'('in lH'

18 TECHNICAL BULLETfN 886, U. S. DEPT. OF AGRICULTURE

BRADENTON FINE SANDY LOAlII.B-Bradenton fine sandy loam was formerly included in the Parkwood series. It, differs from the Park\,'ood in that a 6to lO-inch sandy clay layer is found between the sandy surface soil and the marl substratum, Also the surfacc soil is much lower in organic matter thun the Parkwood.

ROCKDALE ROCKY,AND, CLAYEY PHAsB,-The clayey phase of Rockdale rockland differs from the sandy phase in that the cavities arc filled with a brown to reddish-brown sandy clay. It ig cOllgiciered slightly better for growfng citrus.

ROCKDALE ROCRI,AND, SANDY PH~\gB.-The sandy phase of Rockdale rockland consists of an oolitic limestone which is porous and honeycombed with numerous small ca"ities and holes from 2 to 24 inches or more deep filled with yellowishgray fine sand.

l\L-I.NATBE FINI, SANDY LOA~I.s-?\ranatee fine saIl(h' loam was al!lo formerhr included in the Parkwood series. The surface 10 to 12 inches is black fine sandy loam underlain by 12 to 15 inche!l of a mottled gray fine sandy clay. '''hich rests on a hard marl. rnder natural condition>: thig is a very poorly drained !loil.

FELDA LOAMY FINE RAND,5-Felda loamy fine sand is poorly drained under natural conditions and is charucleri7.{'cl by a dark-gray loamy fine sand surface layer 8 to 12 inches in depth, Thi,; grad('s into a light-gmy loamy fine sand splotched with yellow and browll. At approximately 30 inches is encountered a gray calcareolis sandy clay 1ll0tUe(lwith .,·ello\\' and brown and underlain with marl or limestone.

BLADEN FINE 8,11'.'01' LOA~I.-The ~urftlce of such ::oil to a dC'pth of 5 to 7 inches is a gray or browllish-gra.,' loamy fill(> sand /l:raciill/l: into 8 to 10 inches of a very light gray 10alllY lilll' ~and underluin by It gray IlPa,'y sticky fine sandy clay mottled with brown ext ending tv n dept h of 4 fe!;'1 or more. This soil is a very poorly drained llCid soil under natural conditions.

PAHXWOOD FINE RM\DY LOAM.-Pnrkwood fine sancl\r loam has about 10 to 15 inches of a dark-/l:ray loamy Rand surface Foil grueling'info a Goo to 8-inch layer of a whitiFh marl with inclusion;; of /l:ru." fine sand. This is underlain by a somewhat hardenecl white marl. Thi;4 soil i" poorly drainpcl under natural condifions.

}3RADEXTON LOAllY FIXE S"xD,s-·lkur!enf'on loanl\' fine sand is similar to Bradenton line sanely loam but dj[T('J"~ froIl! it ill that the sandy clay loam layer lies at depl hs tISllally hC'tween 30 amI 42 inehes ancl contains considerable organic matter, 'rhe color of this clay layer i" ;';olllelimes similar to that of tl)e hardpan in the Leon soil.

CLDIATOJ,OCICAI, INFORMATION TN UEI,ATION TO SEASONAL VARIATION

The results obtnined during the course of this study varied con,.. siderubly from srnson to srnson, For rxample, the n;\Ternge total solids content wns lowrl' during H)39-40 and in general higllPr during 1942-43 than during tl1(' othrl' SNlsons, while the nverngr total acid was genernlly lowrr during 1939-40 and Hl41-42 than during 1940-41 and J 942-48. Difl'rrences in f(lltilizntiou and cultural practices could hnrdly account for thr s(>asonal variations found, sinc(' the management of nn individual groye was rNlsonnbl~y uniform. However, 11. review of tlw dimntologicnl ciatrt for the 4 yenrs of this investigation rrY('flis some unusual and rxtreme wenther conditions, which it is beli('y('(1 may have nccolll1trd for the difl'c'rences in the results for the difTen'nt ·spnsons. A yenrly general summary of the climatological data for Florida has bern published by the l'nited States Weather BUl'C'au (29, 30, 31, 32). SOll1r of these data are presented in table 2.

'Tentative designutiollsllbject to ofllriul ~orrelalion by Division of Soil Survey, Bureau of Plant Industry, Soils, and Agricultural Engineering.

--

19 SEASONAL CHANGES IN F.LORlDA GRAPEFRUIT

TABLE 2.-Climaiolouica.l dala for Florida, souih Florida, and various localities in the .staie, 1939-48

.. ANALYSES Oli' VARIOUS PHYSICAL CHARACTERS

COLOH OF RIND

The color of the grn.pd1'lIit rind WflS dd(\rmined hy ffin.tching it with onl' of th{' Htn.ndal'fl ('olors show:n ill plntp 4. EaGh samplC' was

H .---- --~-i ••~.~.• • ZG t= ___ .- - --;--o ~ " ~F -.~- ..~~=:.-z to

~"t~j-

enE ~~-----w I o (1;0 1-o --- MARSH ON ROUGH LEMON ..J - - - MARSH ON SOUR ORANGE

8 c ~~ - DUNCAN ON ROUGH LEMON •~ DUNCAN ON SOUR ORANGE

8

IA AUG.Z5- SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY SEPT. Z 25-30 23-28 ZO-25 18-23 15-20 12-17 11-16 8-13 6-11

PICKING PERIOD

FIG C In; S.-HcnsOl1ul chnll!-(cs ill the n\'crage color of t he rind of ]\[arsh and Dunclln grapefruit 011 rongh klllon and sour orange rootstocks, 1939-43. (Sec pI. 4 for color designations.)

fn.irlv uniform. 1]1 color. N('\"{'rthdl'sS, illdi\"idlln.l values were deLpl'l1iined for Lhe 25 grn.pdrllit,s t.hn.f, (,OlnpriHod ('fwh snmpll', nlld from th!'se an n,\rf'mg(' WUH o\)ULillcd. The results :we prt'sl~nted ill figure 8 and in t:thles 1;'; to 3;~, Appcndix.

DegroC'llillg of gl'n:pefruit was nssoeiated with tli!' ripening of the fruit. This proecss oceulTed ]UtLumlly while t;}w fruit was 011 the tn.'e, and prtwtically :t11 the fruit had d!\grc'ened by January or February. After the fruit WitS degrcened, little change was fmmd in the color of the rind through the remainder of the season. The average of the results showed that during 1942-43 degreening was earlier and that the fl:uit had Ii bcttl'I' rind color than during the procl'ding SClHlons. During 1941-42 the process of degreening was retarded.

20 TECHNICAL BULLEl'lN 886, U, S. DEP'.r, OF AGRICULTURE

The color of the rind was a slightly deeper yellow when the fruits were from trees on som' Ol'flnge rootstock.

Individual groves showed vnrintiol1 in the colol' of the rind from one season to anotlwL Val'iation among g-I'oves 'Nas also noted, The variation among groves of the same variety and roof;slock was about the saml' as the val'iation ,\'ithin i.~Ton's, excrpi, for DunGan fruit on Tough lemon rootstoek. The colnr of t.he rind ,'aried mOI'(l from season to sl'ason within gron's than it did among the sl'v('m1 groves during- th(' same SNlson.

Tests W('I'.' made during two sl'asons on tIll' Fost!'r and thl' Thompson varieties of gl'fl.pefruit. 'rJ.l

Teclmical Bulletin 886, U. S. Department o( A\triculturc PLATE t.

J) G

/J E .H

c I

Stulldurd~ for det('rlllillilll/: the color of I/:J'Ilpcfrllit rilld.

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT 21

ing. USUu.lly the rind Wu.s 1 to 2 mm. thiC'kPr during immu.turity and senility thu.n it wns during the period of prime l'ating condition. There also wcre some indicn,tions of sel1sonnl behavior, since the average thickness of the rind was slightly greater dlU'ing 1939-40 than during 1940-41 and 1941-42.

The fruit hud slightly thicker rinds when the trees were on rough lC'mon roolstock, ond especiol\y whC'n tl)('se trC'es were grown in the light, sundy soils of the ridge district, thun those grown on the hC'aviel' soils of th(' eost and wC'st coast districts. ThC' rind thickIlt'sS of fruit grown on tll(' light, sundy soils rnngr.d from -( to 11 mm., while that of

.. thC' oUI('["s lIsuaHy ronged from 5 to -( m111., us shown in tubles 13 to 31, Appendix, £01' Duncon nnd 11ursh varicties.

'rhe results obtuilled for the Foster und Thompson varic·ties grown in the same districts were similur to those for the ~lursh and Duncan (tnblC's 32 und 33, Appendix).

125rl----~----~----_,----~----~------------~----__--__.

1201-!----- -----:-.----'-- l

1151-1---~--..;.....--- ...., j ::; I ::;110--- • -~----... --- , --~-~--__i

0:

~105f-i----

UJ .

::;

:'!,OO'---- '----:--.:=-=··:::::::::-;.;:;:;;s.;O·;,-~.;;_G-H-l-EM-"O~N---+----lCl

._--'--- ----- ~~:~~N O~:l s~~~GHO:~:~~ ---!-----j 0--_--'>" DUNC'N ON SOUR ORANGE

85~----~----~----~--__~___~____-L____-L____-k____-J

AUG.25- SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY SEPT,2 25-30 23-28 20"25 18-23 15-20 12-17 11-16 8"13 6"11

PICKING PERIOD

FIG UlUJ O.-Hl'a:iomtl changes in the ayerage diameter of :'far"h and DUllcall grapefrllit on rOllgh lemoll lind sOllr orange rootstocks, 1()30-42.

Throughout this illy(·stigution the Jruits of {'neh snmpJe were halved transversely, nncl til(' lexture of the flesh WilS classified. No abrupt chunges in texture w('re noted us the fl"uit 1lllltured. Howevpr, the flesh texture wus distinguis}t('d at c('l"tnin stng('sns: (1) Ricey-textured, in which the flesh had it riceIike npppnrnllce and the juice vesicles eOI1bin('d very small quantities of juiee; (2) cOlll"se-lextul"ecl, in which the vesicle cell walls were thiek and COJlSpieuous and the juice vesicles were not distended with juice; und (8) good-textured, in which the vesicle cell walls were thin aIld inconspicuous and the juice vesicles were fully expn,ncied. The textul"e oj' the J1esh of individuul gntpefruits and of composite fruit snmpies was clnssiiied accordingly.

Immature grapefruit wus ricey n.nd thnt piekeeL between November aneL January was usually coal"se, but that picked nfter Jnnuary or Februnry had good tl'xtUl'e. (Sec fig. 2 unci tn.bles 13 to 38, Appendix.) Grunuln,tion or drying out did llOt develop to any serious extent, although the study wns continued ench scnson unlil the middle of Mny. In JUI1UUl"Y 1940 It fn,pze dn1l1uged fl"uilulld trees in some of the experimental plots. In each sample lhe percentage of fruit that

22 TECHNICAL BULLE'I'TN SSG, U. S. DEP1'. Oli' AGRICULTURE

showed freezing injury was ascertained, and this is shown in tables 13, 15, 17,21,22,24,27,28,29, 31, and 32, Appendix.

The fruit developed good texture earlier during 1939-40 than during the three succeeding seasons; the development of good texture was retarded during 1941-42. Rootstock had no marked effect on the texture of the flesh of ripe fruit, but the results summarized in figure 2 show that the immature fruit had slightly better texture when it was grown on sour orange rootstock. Tlll'l"C was 110 marked difference in the texture of the different varieti('s of fruit from different groves.

COLOR OF FLESH

Progressive changes ill the color of the flesh were determined by observing periodically halves of trnnsYC'rse1y cut grapefruit. The results arc presC'nted in figure] 0 and .ill iablt,s ] 3 to 83, Appendix. It

z o ;:::

."\

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT 23

VOLU~U; OF JUICE

Two different methods were used in extracting the juice from grapefruit during the course of this investigation. During 1939-40 a hand press was employed (fig. 6), but it did not prove very satisfactory because of the difficulty of removing all the juice; therefore, during the last three seasons an electric reamer (fig. 7) was used. Although no difficulty was encountered in removing all the pulp and juice from the grapefruit halves with the rel1mer, no very fast or efficient method was devised for sepal'l1ting the juice from the pulp. The method em:. ployed was to remove the pulp and juice from el1ch individual grapefruit and then strnin the juice tln'ough a double thickness of cheesecloth, applyiog hl1nd pressure to force the juice through. This probably produced some irregularities in the data on the volume of juice, and the results must be regarded as approximate rather thaI,l exact.

The volume of juice WfiS dctC'I'minecl st'paratcly for each of the 25 I grn,pefruits in each sample, and tlte rcsults were computed in terms of milliliters of :iuitc pel' ] 00 gm. of Jl'uit, as shown in tables 13 to 33, Appendix, filld in figUl'e 2.

Immature fruit conLn.ined compal'H.tively small quantities of juice. As the fruit l'ipelwd, t.he volume of juice incl'cn,sed. The most rn,pid ill('1'('HSC occUI'l'ed ill S('ptembt'r n,nd Odobel'. During this p('l'iod the volulllc inel'en,spd from nbout 30 mr pCI' 100 gm. of fruit to n,hout 43 mI. Later in the season the volume of juice in ripe fruit remn,ined rn,ther constn,nt.

'l'hl' summary of Lbe findings illdicl1tes that, on the basis of milliliters of juice per 100 gm. of fruit, variety had some influence. Marsh fruits cOllsisteutJy ('onLnined more juiec than the Duncan. The inercast's mnged from 2 to 4 1111. of juice pel' 100 gm. of fruit. This sligh tly greater volume wns unclou btC'clly due to the practicn,lly!seedless character of the nl ursh vtlrit'ty. Rootstock apparently eliel not in- ' fllH'II('E' the juice eOnLl'Ilt of thc· fruit, since tho differences found were small nud irregular. ,

PALATABlLlTY OJ

24 TECHNICAL BULLETIN 886, U. S. DEPT. OF' AGRICULTURE

reported that rough lemon stor.k commorJy produced two or three times as much fruit as sour orange, but that it was somewhat poorer in quality.

Ripe Marsh and Duncan gmpefruit on sour orange rootstock were rated of equal quality, but on rough lemon rootstock the Duncan was rated superior to the Marsh. (See tables 13 to 33, Appendix.)

The flavor of grapefruit was more uniform during 1939-40, 19'1:0-41, and 1941-42 than during 1942-43. During the last-named season the fruit was rated lower between September and January or February than during the preceding seasons. However, from February to May the quality of the fruit of the 1942-43 crop surpasse(l tha,t of the other seasons, apparently because of greater quant.ities of total solids and total acid found in the fI'uit during thu,t season. During certain crop years there was evidence t.hat a deterioration in quality occurred late in the season in very ripe, fruit, this being more common in the :Mal'sh t.han in the Duncan variety.

TIlt? progressive improvement in the flavor of :Marsh and Duncan grapefruit with maturity alld ripening of the fruit 011 the tree is shown in figures land 2 and in tables 13 to 33, Appendix. In figure 2 three distinct periods of maturity and ripening, A, B, and C, are indicated:

PERTOD A.- -The fruit wus immature during September and October, and the fiavor was very acid or acid to taste. The improvemellt ill flavor was very rapid during this period and showed an increase in numerical values from a range of 20 to 23 to one of .54 to 60.

PERTOD B.-The fruit matured and ripepr!d from November to the middle of February, and the flavor was rated as tart:, pleasantly tart. and pleasantly tart to sweet. During period B t.he flavor ratings did not increase as rapidly as they did during period A; however, an improvement in the flavor occurred as shown by the numerical increase from a range of 54 to 60 to one of 78 to 93. During this period the grapefruit attained sufficient palatability to meet the minimum arbitrary standard of consumer approval as determined b~' the average numerical flavor ratings. The averages computed from all the fruit: samples and for the four crop years indicated that early grapefruit atta,ined satisfactory eatillg quality by about the first of December. In this cOJlnection it should be poillted out that the fruit from individual groves varied as to the datI! of maturity, based on flavor ratings. This information is shown in tables 13 to 33, Appendix.

PERIOD C.-The fruit was in prime eating condition from February to May, and the flavol' was classified as pleasantly tart und pleasantly tart to sweet. During peliod C changes in flavor were less rapid t.han in'period A 01' B. The 1\{arsh on rough lemon rootstock increased in flavor until April but decreased slightly in 1\'[a),; Mar"h fruit on sour orange rootstock "howed no significant change until April and a decrease in fiavor in May; Duncan grapefruit on both rough lemon and sour orange rootstock gradually increased in fiavor throughout the entire season.

ANALYSES OF CHEMICAL CONSTITUENTS ASCORBIC ACID

In view of the importance of the vitamin content of grapefruit in determining its dietetic value, the data herein presented are of particular interest. The highest amounts of ascorbic acid per unit of juice were always found in immature grapefruit. As the fruit ripened, the milligrams of ascorbic acid per milliliter (concentration) of juice gradually decreased i and the lowest values were usually found late in the season. However, on the basis of tot~.1 ascorbic acid per grapefruit the tendency was for the ascorbic acid to increase with the ripening of the fruit, as the volume of juice increased during this period.

Seasonal variations in the ascorbic acid concentration of the grapefruit within and among groves were comparatively small and irregular, as shown in tables 13 to 33) Appendix.

25 '.

I,

It.

•

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

The data obtained on the ascorbic acid concentration are in fairly close agreement with thosc'reported hy }"'l'cnch and Abbott (11). These inw'stigators analyzed oranges and grap('fruitgrown in the north, central, and east coast citrus distriets of FloridlL and reported that the range of valucs for vitamin C s('('med to bear no relation to the district where the fruit was produced. Thoy coneiud('d that this indicated that climatic or geographic featur('s within the section studied wp/'(' not factors of importance. However, certnin other factors whieh affect the aseorbic acid content have been reported. Harding and Thomas (13) determined the ascorbic acid concentration for 390 individual gmp('fruits picked fTom outside and inside branches. Tlwir results show that FIQrida, gra,pet'ruit from va,rious sources has high asco/'bie acid content and that thc concentration is highest in the outside fruit. As a result, of studi(\s in Arizona" JOlWS et a1. (18) stated that it is consistently ('vid('nt that tll(' fruit from trees handled to give a low l1itl'og('n {'olltent at lmrvcst a,re highct· (approximately 20 to 25 peJ'('('nt) in ascorbic acid con('('ntration than tha,t from trees in which a higher nitwgen level prevailed. Difl'l'rences of tbe same ord('r were observed at each harvest throughout the season.

'rhe rootstock on which the grapefruit were grown afl'ected slightly the eonccntrntion of ascorbic acid found .in the fruit. On the basis of milligrams of ascorbic acid per milliliter of juice, the amount was slightly greater when ,Marsh and Duncan fruit were on sour omnge than when on rough lemon rootstock. In ripe grapefruit very little difference was found in the concentration of ascorbic acid of the .Marsh fruit on sour orange and of the Duncan ft'nit Oil rough lemon and sour orange rootstocks; however, a, slightly low('r average nscorbic a,eid concentmtion was found in the Marsh grapefniit on rough lemon rootstock (fig. 2).

The ascol'bicacid results obtained from the pink va,rietics, Thompson and Foster, wpre similar to thosc from 11al'sh and Duncall fruit grown under comparable conditions.

TOTAL ASH

Grapefruit juice is acid in reaction becnnse of the presence of organic acids, chiefly eitric acid. The juic() is also rich in minerul salts in which the basic elements predominatc. Brcause the organic a,cids are destroyed in the pl'o('ess of digestion in the human alimentary trott, the final reaction of the juice is determined by its mineral content. As the basic clemeuts predominatc, grapefruit juice is regarded as a potentially basic, or nllmlille, food.

The percentage of ash in the juice of grapefruit was determined dUl'ing three seasons, 1939-42, and the results are shown in figure 11 and in tables 13 to 33, Appendix.

The ash content of the juice was generally highest in immature fruit. picked about September 1 and gradunlly decrensed as the fruit developed and ripened. In ripe fruit the'.perccntngl's of ash showed little change, although there were indications of a slight increase in very ripe fruit tested in Apl'il.

The findings showed very little seasonal variation in the ash content of :Marsh fruit 011 sour omnge stock, but more vnriotion occurred in the :Mnrsh on rough kmon nnd the Duncnn 011 both rootstocks. OcnemIly the percentage of ash was highest during 1940-41 and lowest during 1941-42.

2G TECHNICAL BULLETIN SSG, U. S:DEP'l'. OF AGRICULTURE

Duncan fruit consistently contained a greater percentage of ash in the juice thn:n did the :Marsh. Rootstock exerted little effect on the ash content of Duncan fruitj however, in the 1fttrsh variety the percentages of ash were consistently slightly lligher when th\( fruit was on sour orange rootstock.

CONSTITUENTS OF ASH 10

Fuller et al. (12, p. 4,) statC'd that CXPN-tS in nutrition are constantly stressing the importance of so 1'C'gulating thf' di(·t that deficiency ailments may be 3yoided. It was pointl'd out thn,l one usually thinks of vitamins in this COlUlN:tion, but tImt it is now l"('

SEASONAL CHANGES IN FLORIDA GRAPEFHUJT\ 27

.... .

.... '

e ~

'

"'" ~ !! .... oS "''C' ~

'"

28 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE

Generally, the grratest amOlUlts of mangallrse were found in the very ripe fruit pick('d in :May. Variety had little if any effect on the content of phosphorus, while usually a slightly grcater amount of manganese occurred in both the ~1u,rsh and the Duncan variety on sour orange rootstock.

The contcnt of iron varied and showed 14.0 definite trend. The greater amOlmts were fOlmd in ~farsh graprfruit on rough lemon rootstock at Fort Pil'rce and in the Duncan fruits on sour orange at Palmi'tto and Vero Bpach; smaller amounts of iron were found in the grapefruit grown at Dayenport.

PECTIC CONSTITUI

------

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT 29

October. During the commercial shipping season pH values increased gradually and more abruptly in very ripe fruit picked in April and MllY.

The seasonal variation in pH values was small during 1939-40, 1940-41, and 1941-42, but it was found to be considerably lower during 1942-43.

The summary of results shown in figure 12 indicates that the active acidity of grapefruit juice was influenced more by the variety than by the rootstock on which the trees were grown. Consistently higher pH values werc found in the juice of the Duncan than in that of the :Marsh fruit. Rootstock hlld little effect on the pH values of Marsh juice, but in the Duncan variety lower pH values were found when the fruit was on sour orange stock than on rough lemon.

Variation among groves was comparatively small, as shown in tables 13 to 33, Appendix.

3.4 -- MARSH ON ROUGH LEMON

---- MARSH ON SOUR ORANGE ~ ~ 3.3

-' ~- DUNCAN ON ROUGH LEMON

0-----0 DUNCAN ON SOUR ORANGE""> 3.2 -'E.. ~ :---- "'" 3. I ...... ::--:::

I

3.0 AUG.25- SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY SEPT. 2 25-30 23-28 20-25 18-23 15-20 12-17 11-16 8-13 6-11

PICKING PERIOD

FIGURE 12.-Sca.

___

30 TECHNICAL BULLETIN 886, U. S. DEP'l'. OF AGRICULTUF..E

The seasonal variation in sucrose was much greater than that found in the reducing sugars. The smallest amounts of sucrose were found during 1939-40 in the Mnrsh fruit nnd during 1940-41 in tlle Duncan fruit. Sucrose increased only slightly with the ripening of Thompson

e~o~~~~~~--.-------------.-------------.-------------~ TOTAL SUGARS

aoo~----------4------------I-----~~~~--+-----------~ /l,..--" ._-------

7.50 t-----------+-----~--~..,..- ---

I

7.00 1------/.-l7...-...-,-;;;..--~".,-=---~~----=-"'---~---1-----------I 6.50 I--/--.".....~ ~ C-""j-.===::::::;;:~r==~.... ... .,,·-l ____ 6.00 V ~

~ MARSH ON ROUGH LEMON

5.50 I --'" ---- MARSH ON SOUR ORANGE 1-----·· ~ -~-. DUNCAN ON ROUGH LEMON

5.00 yz-----------+-- 0-0-----00 DUNCAN ORANGE 1-------1ON SOUR

I4.50 t--------+-----"----t-------+-------! SUCROSE

3.40 t-------------t------------t----=".....==---+-=:~::::---------I---~ ~k:::-. ~ 3.20 I-----------~~---------=-,..,... - - - - - __ _ .....

~ ::::\?""'" .....=-------::::;.--x:::::..-;-· ...I---~----=~--:::-;i ----ll-~~~;::----------==!· ~ 2.60 ~=:=;;::::;:::::::::=t:======t=======~r-..~.,_-----Jv---- ~

2.40 t--------+-------------t--------l------=:~~:-----I

a40r-------+---------t--------~-----~~ REDUCING SUGARS

5.25 t----------+-----------+-------------+~---------l

4.75 r--------r----------+----------=,...~==----------=-=-.~-I

1----------+---------:7..,--',...-:r~.__=co -- - -,- - --~ 425 ~_;.~-~~ 3.75 r-----~------::~-~...~-=----.....-::::::--=::::-::1...---=::==---..:F----------j 3.25~ ~

2.75~

2.25L-------~------L-------L------~ AUG.25- OCT. DEC. FEB. APR. SEPT. 2 23-26 16-23 12-17 6-13

PICKING PERIO~

FIGURE 13.-SeaSOllal chnngp.s in reducing sugars, sucrose, and total sugars of Marsh and DUllcan grapefruit 011 j'ough ]cmOlI and SOLII' orange rootstocks, 1939-42.

gra.pcfl'uit and, ill genernl, the seasonnl trend was low. In the Foster variety a very high sucrose content wus found. The seasonal variation was wider and tlle amollnts of sucrose were grcI1ter during 1940-41 than during 1939-40.

31 SEASONAL CHANGES IN FLORIDA GRAPEFRUlT

Greater amounts of sucl'ose occurred in the fruit on sour orange than 011 rough lemon rootstock, Likewise, DUllcan fnlit contained more Stl('I'OS(~ than th(' 1l11!'sh when the teces were on the same kind of rootstock (fig, 13), A ('onsidcrllblc variation was found from one S(,I1S011 to anotller, ns wdl ns llmong difl'cJ'('nt groycs for the same sC'asOI1. Th('se J'('stdts \1/('['(' mo1'(' pronounced for sucrose than for the red lI('ing sugars,

It will b(~ noU'd 1'1'om figul'e 14 thnt total sugars usually increased in tll(' Mal'sh and DlIncutl fruit during the fall and midsenson but showed n tpndpl1cy to remn,in !'atllN' constant in ripe fruit. The ex('('ption to this was thl:' 1940··41 senson, w\H'n there wns a gradual inel'ense in totnl slIgtll'S dUI'ing th(' entire senson. Seasonal ynriation in totl1J sugn!';.; wn;.; mo(kl'ntC', nllt! th(' nmount wns influenced by the yearly amounts of J'('du('ing sugars lind ~m('rOfl(' t hnt mude up the total sugal's,

'rests on til(' ]i'OSL('l' varid)T wpre made during Lwo seasons, ThC' !'I~sults show(·d thnt.. tilt' fruit ('ollLnilwd n grNIl\,\[' ('ont('nt of totarsugars dlll'ing 19:39-40 t1l1ln dlll'ing 1940 -41, 'l'hompson f!'uit Ll'sted for one S(,:IS01l ollly l'onlnin('(j SIllIIJlt'!' Ulllolints of Lolnl Rugal'S than the ~farsh under ('ompl1.l'I1IJI!' condition".

TOTAL S~)L/l)S

TIl(' Lotal solids (prineipnlly sugars) g(>lwI'nJly increased slightly during tIl(' C'l1r1i(,I' stng('s of Il1ftturity, Aftcr the fruit wns ripe there was n. tt'lldC'IH'Y 1'01' tilt' total solids ('olltl'nt to I'pmain more or less ('ollstnnt. but ,r(,I'y late ill Lhe scason it fl'('qu('ntly d('crensed, (See fig, 2 find tables ]3 to :i3, ApPC'IHiix),

Thl' I't'stllts 1'01' gl'ujwfl'uit I'('ported \ll'!'('in, as well l1.S tbose for Floridn orllngc'S (1.4), ur(' in gl'IU'!'nl ngl'('('I1l(,llt with the findings of Chntp nne! Church (7), who I'cportpd that soluble solids increased from month to month, that the l1eidity of till' juice decreased, and that thpse ('iIllngesin composition took plll('(' more slowly in grapefl'Uit thlln in ornnges, _

Martin (19,20, )21) pointl'd out the influC'llc{' of nitrogen nutrition in alt(,l'ing filII ('olon1.lion nne! maturity of ~·lnrsh gm.pefruit, He found t.hat fruil fl'om tn'ps of low nitrogt'l) ('ontl'lll in the fn.11 developed ydlow color Jllu('h ('ndi('I' thun thnt from tn·(·g high in nitrogen, At the SflIilC' (inw sOlll('whaL S\\,('('«'I' fruit, as llleHS!l!'e

--

--

--

32 '1'ECHNICAL BUL'LE'l'TN 8813, U. S. DEPT. O,F AGRICULTURE

There was a greater variation in the total solids cont.('nt of the fruit from on(' S('llson to another within the Sllmc gl'OVCS thllll WllS found

l.s II

x--x 1939 - 40 12 ---_ 1940-4,

_1941-42

v-------1' 1942 - 43" I--- 1939 -1943 10

9

I --+-- - ~--~, --- I -8 b- • 1- =--J

7 X-j ! ~i- 1--1

13

I12 iI i --~ " ~

= -~. ~--=:;---~ 10 .., - - 1----.:;:'.:._I-Z !- ---- --t::::::~,,-!__W 9 I ~--o ~ Ioa: I ~ 8 i

B ! I I

---

- -

SEASONAL CHANGES IN FLORIDA GRAPEFRUl'l' 33 t.e

.__!1939-40 2.0. ---_ 1940-41

_1941-42 1.8 9---.v 1942-43

~ -- 1939-1943 1.6 ~~ --~-- --f-- I'1.4

1.2

"'-,r----... -......:: 1----= '-- -=.:::.:: ~ r--- --- 1 .~~ ~ -~1.0 0.8

A I ~ 2.2

2.0 ., 1.8 .'"r~j: 1.6

Z ' -...w '"- ... ,~~~ ~ 14 --- -----~ w R - . -.:::.: ~ ~ 1.2

~ -

I-ZLO I t---""""'" ~ w I -r----::::B Z 0.8 0 (.)22

0 (32.0. .q I;i 1.8 I- -..., -~-~ 1.6 -i_I

1.4 ~ ~ -- -- ,---- --,!--.r---J--=: t-=====:~ 1.2 - - ...I... .1JJ I f-'::: -{' O.B

2.2

r-....2.0

I.B ~ ~-----

I.e

~~----I ----- r----r-- ~ .........

~-----~ 1"---- t--::.--- -1.4 ~

1.2 - i~

'1.0

D O.B

MAR. APR. MAYAUG. 25- SEPT. No.V. 20.-25 19:~3 1~~~6 11-16 8-13 6-11SEPT. 2 25-30

PICKING PERIOD

FIGURE 15.-Seaso.nal changes in average to.tal acid co.ntent, of grapefrui ', 1!)30-43: A, l\Jarsh un rough lemo.n ro.o.tsto.ck; B, Marsh o.n so.ur o.range; d• Duncan on ro.ugh lemo.n; D. Ducan o.n Bo.Ur orange.

http:ro.o.tsto.ck

34 TECHNICAL BULLE1'lN 886, U. S. DEPT. OF AGRICULTURE

and Duncan grapefruit for 1939-40, 1940-41, and 1941-42 were analyzed statistically, as shown in tables 13 to 33, Appendix.

TOTAL ACID

A downward trend in total acid generally characterized :Marsh and Duncan grapefruit as the fruit ripened. Figure 2 shows the summary of results. The n.vemge totnJ acid mngcd from about 1.70 to 1.89 for immn.ture fruit to about 1 to 1.28 percent for very ripe fruit late in the st'asoll.

The seasonal difi'er(,lwes were rathcrpronouneed, and the averages were gen('rnlly lower dUI·ing 1939-40 and 19

SEASONAL CHANmJS IN FLORIDA GHAPEFR1HT 35

RELATION OF ARSENICAL S}lRAY LAW TO GRAPEFRUIT

The spraying of gmpcfl'uit trees with lead arsenate is a common practice in Florida., dating buck to the. time when the. spray was used as a control for insect infestation, It is no longer used fol' this purpose and the quantity of arsenic applied is suIlicient to leave only barely detectable tesiducs, if uny at all, OIl, the rind of the fruit at time of harvest, In carliN' timC's, howo\'C'r, wlH'1l lead ai'senate 'was used for insect control, growers ohsl'ryC'd thnt thC' fruit from spmyed trees contained less acid unci SN'Jl1l\d swC'C'ter than that from trees not sprayed with lead ursellatf\; Ull'r('for(\ til(' sprny ('nnl(' to be used solely for the purpose of obtaining s\\,('(\1(\r fruit, '1'hl' infhwllce of tlll' arsenute sprlly in low(,l'ing thp n('idily of tltC' fl'uit llPPC'Ul'S to be systemic in the tree and is C'xPl'lc'd Inl'gC'ly from dpposits on the leaves rather than on the fruit, Th(' physiological basis fol' thp effect is,still obscure,

Inj udicious use of lead ill'SI\nll l(' on \'nrious types of cib'us trees in . order to eHe('l an Nldil'l' allainnwlIt of legal matU1'ity of til(' fruit promptpcl th(' Flol'idlL Stu.tp L('gislntul'(\ to pnss till' AJ:senicul Spray Law (22, p, 5), which .is brielly d('scribed as follows:

AN" ACT to Prohibit tll(' ('fi(' of Arsenic or All\" of Its Dcrivatin's or An" Combination, Compollnd or Pr('parntion COlltainilig Arsenic, as a Fertilizer cir Spray on Bearing Citrus Trees; to Prohibit nIl' Sal(' or Transportation of Citrus Fruit Containing Any Ars('Ilicj and to Proyide for Enforcement Thereof.

• In 1929 the 1h·ditel'l'unean fruitfly mude its appearance, and arsenic was the only efl'l'ctive poison known itt that time fo1' its control. Consequently, IUl amenduwnt to tilt' Arsenical Spl'llY Ln.\\' was approved June 29, 1920, giving the Fedel'llL GovermuC'nt and the FLorida State Plant BonI'd the right to usC' nrsenic: for the purpose of erndicating the fruitfly, This IImendnH'nt IH'C\-C'ntcd the enforcement of the law until Janunry 1, 1931. Betw('l'n 1\)29 lind 1932 much investigational work wus done by the Florida Stutl' Department of Agriculture (22) to as(,t'I'tuin the eff(\('ts of fll's('nieals on citrus fruits, Ii; wns found that the flnvol' of grnpefruit npparently was not lowered by this sprlLy, wherPlls its injudkious US(\ Oil oranges and tungerin('s cflused a very milrked decl'pase in totnl neid und produced flnt, insipid, poor-quality fruit, Therefor£', i" 10:33 gmpefl'uit wus exempted from the Arsenical Spray Law (10, p, 11:3), through an ", , , injunction granted by Circuit JUclg(' H, C, j>ettawn.y, , , and uph('ld by the Supreme Court, l'estraining til(' Department of Agriculture from the enforcement of the Citrus ArsC'nical Sprny I.Jaw in til(' (~as(' of grapefruit,)) so that now this law is appliNI only to omngC's find tn.ngerinl\s.

On this n('('oullt ('oml)J'ehensin' ill"n'stigations wcrt' muck to obtnin more completei11fol'mation on the ell'pcts of spmyillg in ,July with lead arsenate (usuillly n.t the rflte of 1 pound to 100 gallons) on the composition unci internal qunlity of 11nrsh nod Duncan grapefruit, In tablcs 5 to ] 2 the piJysi('al characters und ('1Iemical constituents of these Yal'ieties on rough lemon and SOUl' orange rootstocks when unspru.yed und when sprayed with lend arsenate are directly compared and the difl'('l'cncl\s resulting from the Spl'll)' urc shown, The interrelations of the. physicnJ cbaracters and cJlcmicnl constituents of the individual vnrietY-Tootstock combinntiolls wIlen unsprayed and when sprayed with lead urscnntp ttt the different picking periods throughout the season m'e shown in figures 16 to 19,

----------

----

--

---

36 'l'ECHNICAL BULLE'l'IN SSG, U. S. DEPT. Olo' AGRlCUVl'URE

12 TOTAL SOLIDS TO ACID

II

10 .... ....0 ~----fi

9 ----- 0:: ---- -8

7 --6 ~ 5

t- 4 Z TOTAL SOLIDSW 10 0 --- -0:: 9 w rQ. 8

1.8 TOTAL ACID I- ... :::--.....1.6Z UJ

1.4 ',-,

0 a: - - --W 1.2 -- -Q. - ----- - -- t--... ---1.0 a:o.e",W ::!!t: I'..... ,.,,~CORBIIC ACID ct..J 0:::::;0.4 --

0.35 -"V .~

30 WEIGHT PER FRUIT

550

--~-~ ---- 500 "'450 ~400 .-~ 350 ...,..., -~

~ 300 L250

200

---- --- -85 FLAVOR (TASTE) OF FRUIT 80 ........

75

---- -..--::. .....V--- ~-M;;;M~,r-S-,.:rmARD--='=' Z ~ a:

70

65

1--- --- --....

--- -- V 7 OF ACCEPTABILITY ..J ct

60

55 ,."":"'---0 ~ a: w ::!! :;)

z

50

45

40

35 / f

d

30

25

20 V "./

AU G. 25 - SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY SEPT. 2 25-30 23-28 20-25 18-23 15-20 12-17 11-16 8-13 6-11

PICKING PERIOD

FIGURE l6.-Interrelation of physical charaeters and chemical constituents of Marsh grapefruit on rough lemon rootstock, when unsprayed and when sprayed with lead arscnate (1 pound to lOO gallons), at different picking periods throughout the season. (Averages of all seasons, 1939-43, and. all groves.)

-----

---

----

--------

----

37

•

•

.~

SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

3 ~ ......TOTAL SOLIDS TO At D

II o (;i 10

2

-- - -;,;

- ----P' 9a: 8 ---- 7

St;.7"- - - .... 2 5 ____ TOTAL SOLIDS ~ 1 -- - -a:

I __ ;..-0'" 0. TOTAL ACID .0 .B

""-... ...............

~ I .6

~ I .4

a: --- --.2 - --i----- -0. '" .0 i 1- - o.B -

ASC01BIC ACID

ffi 0.6 0. a: ~ ~~O.5

--

-- ---

- -

----- --

--

38 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURE

I TOTAL SOLIDS TO ACID

0 -_.....--- o 9 f; 8 f-.

_I

a: 7 ....1 61--;:"-

I ~ TOTAL SOLIDS Z

Ul

(.) 0 a: - -"'" 9-Ul a.

8 TOTAL ACID

l-

8

6 '-......

Ul

....... rs q(.)a: ----2 a. 0 -- ---- --

AS90RBIC ACID

~1-q -- -3

VOLUME OF JUICE ~..-5

UNSPRAYED0 //

,/

",'" ------- SPRAYED

30 ;/

WEIGHT PER FRUIT 700 1----650 V':: 600

--:::::. ----- ~,III

:0 550 --.:::-:.~ 500 -. -~- •Cl 450 ~ 400

~ 350 ..".-, 300

FLAVOR (TASTE) OF FRUIT -----B5 --

" 80

--,'/ ---- ----Cl 75

Z 70 ;.....---- -------t:---..: ~-~ --- --

-' MINIMUM STANOARD!;i 65 7 --_. a: f-- OF ACCEPTABILITY

60

..J ..,./--' '.--1. I ~ 55 (.) //

.a: 50 // ~ 45 1//::J 40

Z ./ V35

~ 30

,~25

20 1/ AUG.25 - SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. M/I1f SEPT. 2 25-3C 23-2B 20-25 IB-23 15-20 12-17 11-16 8-13 6-11

PICKING PERIOD

FIGURE 18.-Interrelation of physical characters and chemical constituents of Duncan grapefruit on rough lemon rootstock, when unsprayed and when sprayed with lead arsenate (1 pOllnd to 100 galJow.;), at different picking periods throughout the season. (Averages of all seasolls, 1939-43, and all groves.)

-- -- ---

-- -

----- ----

39 SEASONAL CHANGES IN FLORIDA GRAPEFRUIT

TOTAL SOLIDS TO ACID -9 ~---0

_---18 ---- , ~

7

61-_ --- - ,I 5t;..--

I - 2f.....!9TA'- SOLIDS -- ffi ·1 I I __6:0-- I ~ I IJJ 0 I Q.

2 o TOTAL ACID

. 1' ....- ......... ---.6 .4 - ---

I ----

ASCORBIC ACID 5~

.~

4 I --VOLUME OF JUICE -~-

j-.

3

- ----- ----- --- 5

.I' V- ,/'/

0

.I'~ '" ,."/

°v 25

WEIGHT PER FRUIT ~ 600 -550 f='- - ---I ~ --500 , ~-

III 450

~ 400 ~ -I '"'" UNSPRAYED Ig; 350 I="" ------SPRAYEDI I;;0 A -0L.4'.... ,I250 I I I200

FLAVOR (TASTE) OF FRUIT I 90 --=- ..85 ---BO

I --- V- I 75

.... I C> Z --- -Ir --70 --- ----r~ ....-- --~ 65 -~:;;;;,;u;- ;T:;':R";" r / OF ACCEPTABILITYa:: l.-- ...J

60 ....?? I z 40 V i f

35 /~ I

30 .?/'

25 V20

AUG.25 - SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY SEPT. 2 25-30 23-2B 20-25 18-23 15-20 12-17 11-16 8-13 6-11

PICKING PERIOD

FIGURE 19.-Interrelation of physical characters and chemical constituents of Duncan grapefruit on sour orangc rootstock, when unsprayed and when sprayed with lead arsenate (1 pound to 100 gallons), at different picking periods throughout the. season. (Averages of all seasons, 1939-43, and all groves.)

40 TECHNICAL BULLE'.rIN 886, U. S. DEPT. OF AGRICUL'l'URE

TABLE 5.-Effect oj lead arsenate spray on the average weight ojgrapeJruits at different picking periods, 1939-43

[+ indicates tbat weight o( sprayed fruit was greater than that of unsprayed; - that it was Jess]

"~----- ._---Weight p~r fruit

Variety, rootstock, and treatment

•

TAllLE 6.-Effect of lend arsenate spray on the average volume oj juice in 100 grams Ioj grapefruit at, different 71icking periods, 1939-43 [+ indicates that sprayed fruit contained n greater volume of juice than unsprayed; - aomaller volume]

I Juice per 100 grams of fruit Variety, rootstock, and \ I "• I I ' ' I '

treatment j A Ug. I ~ . . T .". • r I tI 2';- I Sept. Oct.. N0"l Dcc. I Jan. ! Feh. 1\[ar. Apr. May\SCI;t. 2\ 25-30 23·28! 2O-2-'i 18-2:\, 15-20 12-17 U-16 7-13 6-tt

_________1__1__._,_1______1________ Marsh on rough lemon: MI. MI.: .HI. [,\[1. MI. ,\fI. 1 ,\fI. }.fI. }./l. Ml.

Unsprayed............. a:l :1.1 45 I 45 41; 47 49 50 51 51I-Spruyed.................. a:1 37 44! 46 46 47 49 48 _ 50 51

1,larsl~:::::r~~:~;~;·····.. 0I :2) -I I +1 0I 0 0 -2\1 -I: ° Unsprayed... ••••••••••. 31 :l~ I H i 4~ 47 \ 50 51 5~ ~I 52

Sprayed.................. 29 I ,110 I Hi, 41 48 1 50 51 5* : 03 54

Pifference.............. -------1--1----I ~L +1 +1 0 I () +1 +2 +2-2! DunClul on rough lemon: _.!. (' I ..-

Unsprayed............... :10, 34 i 4.1 44. 44 46 46 46 41 48

SPr~Yed.................. :l~ L--~I~I--4-41'~~~~l~~

DIfference.............. ---..±.:..1-.::!::::.1__O____0 ....±'...l~ __0___0___0____0

Dunclln OIl sour orange: ---1--1--- ---1-- ---,--- ---)-----

C"nsprand. .............. ~7 ! :I~ : 42 4" i 4~ 4~ 46 4~ f 49 48

Sprayed ................ ~!~1__44_ ~.~j~\~__41_\~~

Difference.............. +31 __+:1 I . ~~_~J_:~~L~2L__~1 +1 I +1 +2

41

----------------------------------------

SEASONAL CHANGES IN :FLORIDA GRAPEFRUIT 41

TABLE 7.-Effect of lead arsenate spray on the average percentage of grapefruit that was juice at different picking periods, 1939-43

[+ indicates that a greater percentage of sprayed fruit was juice than unsprayed: - a smaller percentage)

Juice per fruit

Variety, rootstock, and

treatment .\~.

! : Sept. Oct. !No\·. Dec. Jan. Feb. Mar. Apr. lIIay

Sept. 2: 25-30 23-28 20-25 18-23 15-20 12-17 11-16 7-13 6-11

Marsh on rou~h lemon: Pel. Pd. Pd. Pd. Pd. Pet. Pd. Pet. Pd. Pd. Unsprayed ...•. 33 36 46 47 47 49 50 51 52 53 Sprayed...•...•....•.••• 33 39 45 48 47 49 50 50 52 53

Difference•••••.•• o -I o o o -1 o o .M arsh on sour orange:

UnsprRycd~_~ 32 :18 45 48 49 52 53 52 52 55 Sprayed._•••••. 30 37 45 49 50 51 52 54 55 56

• Difference.• -2 -1 o -I -I i==========

Duncan on rough lemon: Unsprn:n1d, - 31 3.1 45 46 46 47 47 47 48 50 Sprayed._._••. 32 37 45 45 46 47 48 47 48 50

Difference.. o -1 o o +1 o o o ==========

Duncan on sonr orange:Unsprayed.. ..• 29 34 44 46 47 46 48 48 51 50 Sprayed. ........... •••••• :11 37 45 48 48 48 49 49 51 52

Difference.............. +21~ -=i=l---=i=2 -:;::1---=i=2 -:;::1-:;::1--0-4=2

TABLE S.-Effect of lead arsenate spray on l.he average ascorbic acid concentration per milliliter of gmpe!rllit juice at different picking periods, 1939-43

1+ indicates that ascorbic acid content: in sprayed fruit was greater than in unsprayed: - that it was .less)

Ascorhic acid per milliliter of juice---.,---,--_._.._-_._----_.__._-- -;----;----,--

Variety, motstock, alld : i ,

treatmcnt : ...~ug. : R!'pt. I Oct. : Xo,-. Dec. Jan. I Feh. Mar. Apr. May

:~.-5- ~, 25-30 ' 23-28 120-25 18-23 15-20 12-17 11-16 i-13 6-11,.,cpt. - . ------_.- --------------------Marsh on rOllgh lemon: MO. MO. J\[g. l\fU. lofg. ~fg. lofU. .Vg. l\fU. l\fU.

enspraycd I n.49 0.42 0.41 0.39 0.:18 0.3i 0.30 0.35 0.34 0.32 Sprayed.••••. .50 .43 .41 .41 .39 .38 .3i .36 .34 .32

Ditrcrence ••••. +.01 +.01 -:00 +.02 +.01 +.01 +.01 +.01-:00--:00 ==========

1\1 ursh on sour oran~e: Unsprayed... .51 .4i .44 .42 .42 .42 .42 .40 .37 Sprayed•.•... .49 .4i .46 .44 .42 .42 .43 .39 .37

Difference .00 -.02 .00 +.02 +.02 .00 .00 +.01 -.01 .00 =1=========

Duncan on rough lemon: Unspraycd.. . .50 .41; .44 .43 .42 .41 .40 .41 .40 .38 Spmyed..... . .49 .46 .45 .44 .43 .42 .42 .42 .40 .38

Difference.••. -.01 +.01 +.01 +.01 +'01 +.01 +.02 +.01 .00 .00 =========:;==

Duncan On sonr orange: Unsprayed. • • .. .53 .46 .45 .44 .43 .43 .42 .42 .40 .38 Spra~·ed•••..•.•••••. .52 .46 .4-1 .44 .43 .43 .42 .42 .41 .39------------------------.,-------

Diffcrence............. -.01 .00 -.01 .00 .00 .00 .00 .00 +.01 +.01

-----------------------------

------------------------

---------------------------

---------------------------

---

---

---

42 TECHNICAL BULLETIN 886, U. S. DEPT. OF AGRICULTURJ

SEASONAL CI-IANm~s IN FLORIDA GRAPEFRUIT 43

TABLE ll.-Rffect of lead arsenate spraJl on the average ratios of total .~olids to acid in qrapefrldts at different 1)icking periods, 19.'39-4.'3 •

l+ indicates that the total solids-to-acid ratio was greater in sprayed fruit than in unsprayed) ----------,---.---.~-- ------.-_._._- ,.--~--.--------

Solids-acid rutio

Variety. rootstock, and treatment, -'2.~·IS,·pt.1 Oct. : XOY. i Dee., Jan.. 1Feb. lIrar.1 Apr. May

~ It?' 2f...:IO 2~-28 20-2.1' 18-~ If...2O I 12-17 11-16 7-13 fHI ..,e J • -I ii, ! '

-----------.'- ---'---- ---'--- ---1-.--:--- ---,--- ---Marsh on rough lemon: I '

Unsprnwc! l 4.95; O. wj h_ 10' n.4·1 r..79 I h. \~i I •. an ,. n4 1 8. II 8. 92 Sprayed __ _ __ I 5.2S· n..;'" n.H" 7.50 7.91 1 s.:m' 8 . .'\7 9.08 I 9.93 11.04

DUTerNlc,' _j +. ;1:1 ~+.:l~ =+.82:., +I!~ ±I. 12 I~l. 40 1+1.21 1+1.44 ~1.82 +2.12 ?-rnrsh on &llIr orunge: I I' " ! Il'nsprnyed. _______ . ___ Ii. 08 0.35l 0.40 6.0\1, •. 77 f •••4 I 8.23 8.n8 9.35 9.52

S]lrayed • _ _ _ • 5.81 0.88 7.2.;: 8.12 s.m \1.:12 9.•9110.41 11.34 12.,5

Difference _;~!+.5:l +.,111 +1.lal~ +I..iS 1+1..111 1+1.7:11+1.09 +a.2~ Duncan on rough lemon: 1=1==1=1= '="--=.--= ~=I=I=

Unspmy..d __ /4.00 5.85 6.14 6.4710.79 G.81 7.09; 7.291 7.701 8.23

Sprayed . ~ G..18 G. 82 I~:~~ __~~_L9.21, 9.04. 10.48

Difference ,+.49 +.7:1 +.ns 1+1.09' +.94 +1.36,+1.3.; :+1.92 '+1.94 1+2.2.; 1'""="""'='='=======

Duncan on ~nur orange: I 1 r. - I - ! ! - 1 - '- I _ I Ullsprn)~d . _____ r 5.14, ., •• 41 .;.6. I G.on 0.3, I n.n.1 fl.9S ,.39 1.53 8.0.,

Sprayed. . .• _ I 5.4i G.52 O. na i.06 I i. i5 7.11" 8. (l4 8.00, O. i2 9.98

___D!ff~~enCe .. J~3:1 I +. ;SI +:9G +.97 ~1~S :+L~O +J:6I11+I:57l+2:l9r+1.93

TA HLP. 12.-Eff(ct of lead arsenate spray on the average flavor, or taste, as indicated by n1l"lllericall'athlgs of grapefruits at different picking periods, 19.'39-43

r+ indicates [ncrense in flayor ill sllray\'c! fruil; -decrease in flavor)

,,\,merien! ratings (flamr, or lnste,)

-----------._----Variet:r;:~t~~~riik. and ! A lIg ,.,! I' 1

I ?5-' Sept. Oel. i No,'. I Drc. j' Jnll. j' Feb. lITar., Apr. May !::(:pt ~ 25-30 2:1-28' 21f--25 I 18-23 If,..20 12-Ji 11-16' ,-13 6-11 -----------'t-'--·--I--- ___'___'___1___1__