Chocolate success: controlling its 'temper'aocs.files.cms-plus.com/inform/1998/09/872.pdf · Nestle in Switzerland and Cadbury's in England developed milk chocolate products. ...

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MEETINGS

Chocolate success: controlling its 'temper'The Process Engineering Group of theSCI and the Institute of ChemicalEngineers joined together for acheese-and-wine evening at the SCIoffices in Belgrave Square, London,on June 9. This report is by KurtBerger, a consultant based in London.

B efore indulging in a liberal pro-vision of food and drink, the 35participants in a cheese-and-

wine evening enjoyed a lecture onchocolate by the technical and pur-chasing director of Cadbury Ltd ..Peter Hebblethwaite.

The cocoa bean is native to theheadwaters of the Amazon River andwas cultivated by Mayan Indians.However, Europeans first came intocontact with cocoa in the 16th centurywhen the Spanish invader Cortez vis-ited Montezuma at the Aztec court inMexico City. He found that therecocoa was a highly prized commodity,which could be used as a currency.

After roasting, the bean was mixedwith maize and chili powder and madeinto a luxury drink-hot chocolate, inevery sense of the word "hot."

Cortez introduced the cocoa beanto Spain in 1528 and it continued to beimported in small quantities, spread-ing northward after about 100 years. Itwas valued in Holland as a stimulantand medicine. During the 18th centu-ry, grinding techniques improved andin 1828, Van Houten introduced a fil-ter press to separate the fat from thecocoa powder. The mixing of this fatwith more ground beans and sugar ledto the development of chocolate.

Soon there were 27 chocolate fac-tories in Holland. In 1835, Peters andNestle in Switzerland and Cadbury'sin England developed milk chocolateproducts. In the United States, choco-late manufacture was pioneered byHershey. The industry in the UnitedKingdom was dominated by threeQuaker families, Cadbury in Binning-ham, Fry in Bristol, and Rowntree inYork. As nonconformists, Quakerswere excluded from the universitiesand the military at that time and there-fore turned their considerable talentsto commerce and industry. Cocoa. as

the basis for a nonalcoholic drink, fit-ted in well with their philosophy.

The cultivation of cocoa was suc-cessfully introduced into The Philip-pines and the Indonesia island ofSulawesi during the 16th century, butreached West Africa only in theI870s.

The beans are produced in largeoblong pods, 40 beans per pod, on asmall tree. Conditions for producing thecrop are 2,000 sunshine hours and1.300 mill rainfall per year, within 20°of the equator. and average tempera-tures of 22-32cC. The rainfall shouldbe evenly distributed except that a dryspell improves fruiting. The tree is diffi-cult to grow, requires panial shade, andis prone to disease and pests so that upto half of the crop may be lost. Cocoa ismainly a smallholders' crop.

Preparation for shipping consists ofextracting the beans from the pod andthe surrounding mucilage, allowingthem to ferment naturally in a heapcovered with plantation leaves for fivedays. During this time, the heap isturned to avoid overheating. Next thebeans are spread on the ground andsun-dried before bagging up and dis-patching.

Current world production of cocoabean is estimated at 2,8 million metrictons, with more than 60% from WestAfrica. Production in 1996 in the pri-mary production nations was: IvoryCoast, 1,126,00 metric tons (MT);Ghana. 326,000 MT; Indonesia,310,000 MT; Brazil, 165,000 MT;Nigeria, 162.000 MT; and Malaysia,98,000 MT.

The United Kingdom market forchocolate confectionery products isworth about £3.5 billion ($5.75 bil-lion) a year, significantly larger thanthe market for bread, milk, or newspa-pers.

The production of chocolate frombean involves first roasting, whichdevelops the flavor initiated by thefermentation step. Next the shell isremoved and the nib is ground. Theresulting cocoa liquor is blended withsugar, condensed milk, additionalcocoa butter, and lecithin to createchocolate. This blend is subjected to

conching, a unique process in whichthe product is worked with a heavyroller. This alters the flavor and tex-ture in a desirable way. Before thechocolate is allowed to set either inbars or as a coating on enrobed prod-ucts. it must be "tempered" to obtainthe correct polymorphic form of thefat phase. Cocoa butter is unique inbeing able to crystallize in six distinctforms of successively increasing melt-ing point. Only form 5 gives a choco-late of good gloss and smooth eatingproperties. To reach form 5, thechocolate is heated to 50°C, cooled to26cC, and warmed to 30°C before till-ing into molds or enrobing. This treat-ment induces crystal seeds of thedesired form.

When chocolate is subject to fluc-tuating temperature during storage,the tendency 10 move 10 the thermody-namically most stable form 6 assertsitself, and the surface acquires a dullor whitish appearance as form 6 crys-tals grow out from the surface. Con-sumers often confuse this appearancewith mold growth. Eventually the fatthroughout the chocolate reaches form6 and the mouthfeel is dry, powdery.and quite unappealing.

In the United Kingdom and a num-ber of other nations, products labeled aschocolate may contain up to 5% of veg-etable fat other than cocoa butter. Thisaddition enables the physical propertiesof the fat phase to be adjusted 10 takeinto account the natural variation incocoa butter, but the fat used must havea glycerides structure compatible withcocoa butter. In practice, the fats usedare usually derived from tropical nuts,such as shea and illipe. and from palmoil fractions. Addition of such veg-etable fat in chocolate is not pennittedin some countries of the EuropeanUnion and continues to be a subject ordispute.

The various stages of production ofthe cocoa beans and chocolate werecopiously illustrated with slides inter-spersed with video action shots, andthe properties of the product weredemonstrated with samples for theaudience. Needless 10 say, the lectureand the samples were thoroughly

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applauded, not the least by severalschool children in the audience.

'Young Authors' meetingattracts 15 presentationsOn July 7, 1998, the Oils and FatsGroup of the Society of ChemicalIndustry, jointly with the Royal Soci-ety of Chemistry, held a one-daymeeting for presentations by youngauthors. This TetJO" is by Kurt Berger.a consultant based in London.The Young Authors Meeting providesa biennial opportunity mainly for doc-roral students in relevant fields tomeet and present their work. At the1998 meeting there was a full programof 12 oral presentations and threeposters.

Chris Firman from Reading Uni-versity is studying the analysis of stig-mastadiene in olive oil. This com-pound is formed from /l-sitosterol inthe refining process and can thereforebe used to detect the presence ofrefined olive oil in the more expensivevirgin grades. A European Union reg-ulation specifies a maximum stigmas-tadiene content of 0.1 5 mglkg in thevirgin grades and gives an analyticalmethod involving saponification. col-umn chromatography, and gas chro-matography. However, both saturatedhydrocarbons and squalene interferein the final chromatogram. Finnan hastherefore introduced a purificationstep, using a bond elute cartridgeloaded with silver ions to separate thestigmastadiene-comaining portionsfrom both the saturated and the highlyunsaturated hydrocarbons. The rele-

varu fraction is finally analyzed by gaschromatography, and cholestadiene isused as an internal standard. Finnanalso investigated the formation of stig-rnastadiene during the various refiningsteps. Some formation occurs duringbleaching. depending on temperatureand on the amount and activities ofthe earth used. Deodorization alsocauses some dehydration of the sterol.depending on temperature. The activa-tion energy of dehydration was calcu-lated as 145 kjoulelmole.

Graham Bennett from NottinghamUniversity investigated the use of theMaran low-resolution nuclear magneticresonance spectrometer. This instru-ment has an enhanced pulse program-ming facility. The magic echo pulsesequence enables solid fat content to be

[continued on pagi! 875)

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[continued from page 873)

measured directly without the use of anI-Iecror. The results for a tristearill-lri-olein mixture were more accurate thanthe normal measurements. Bennettfound incidentally during his work thatthe signal decay time of the p-poly-morph is much longer than that of the aform

Stephanie Dudd from the Universi-ty of Bristol has analyzed fatlyresidues extracted from pottery foundin various archeological sites in theUnited Kingdom. The residues were amixture of fatly acids and mono-, di-,and triglycerides, resulting from thedegradation of food fat over time.Carbon 13 stable isotope analysisreadily distinguishes between pig fatand the body fat of ruminants. Thelow-molecular weight compounds thatare characteristic of milk fat were nOIfound, presumably because they hadbeen leached away by percolating rainwater over time. However. the isotoperatio of milk fats was found to bedifferent from that of the adipose tis-sue fats. because of their more directformation from forage lipids. Theanalysis can therefore be used todetect the early use of dairy products.

After lunch. Adil Abdul Hamidfrom Hull University described hisstudies on lipid synthesis in fungi.Malic enzyme is an importantprovider of NADPH. Hamid was test-ing the hypothesis that malic enzymeis part of a multienzyme cluster alsocontaining fatty acid synthase andother enzymes involved in lipid syn-thesis. When cells were centrifuged at100.000 x g, malic enzyme was in thesupernatant. while fatty acid synthasewas in the pellet. This suggested thatat least some of the malic enzyme isfree in the cytosol and that the syn-thase is bound to the cell membrane.Lipid synthesis in Mucor circinel-loides is almost completely inhibitedby sesamo!. extractable fat beingreduced from 24 to 2% by weight.Growth of the fungus is also inhibited.

The next speaker presented a tech-no-economic study of olive oil pro-duction in hcr home country of Crete.Agapi Vassiliou is at the Welsh Insti-tute of Rural Studies in Aberystwythand is comparing the conventional

with an ecological or "green" produc-tion method in collaboration with agroup of Cretan farmers. From dataobtained in the field. she finds that aviable income can be obtained by eco-logical production from 5.77 hectares.Although labor requirements are high-er, the cost of chemical inputs isreduced. Overall production costs are

somewhat higher and would have tobe recovered by the higher retailprices available for "organic" pro-duce. Vassiliou developed an input-output model to determine the effecton other sectors of the economy andon the overalt economy of Crete.

Hazel Mottram from Bristol Uni-versity returned to an analytical chem-

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isrry topic. the analysis of fatty acid inthe slI-2 position of the triglyceridemolecule. She reviewed the availablemethods. the most usual involvingenzyme hydrolysis and then describedher work with high-pressure liquidchromatography in combination with

atmospheric pressure chemical ioniza-tion mass spectrometry. The spectraobtained for a lriglyceride are simple.showing a protonated molecular ion(M + H)+ and a "diglyceride" ion [M- RC021+. The Lj-diglyceride is theleast abundant, possibly due to some

stenc protection of the sn-2 position.and hence the position of fatty acids inABC-type triglycerides can beobtained and the ABA triglyceridescan be distinguished from AAB type.Application of the technique to soy-bean oil, pork fat, and lamb fat gaveresults which agreed well with lipaseanalysis. Milk fat. with its large num-ber of triglycerides, presents a moredifficult problem, but progress isbeing made by analyzing fat fraction-ated into groups of different molecularweight.

Ii i~§ BAFl:/fJ11:~EJJfjli~~B{jRet..1 ;~~Jj,1~~~~:~ei~~:fi~~lactobacillic and mycolic acid. Theircis-I,2. disubstituted cyclopropaneunits are chiral, but the absolute con-figuration needs to be established.Coxon described his approach to thesynthesis of lactobacillic acid ofknown configuration and the prepara-tion of derivatives with enhanced opti-cal activity,

The SO-carbon compound mycolicacid is a component of the tuberculo-sis bacterium. The compoundthicbactomycin inhibits the formationof a-mycolic acid at two sites of itsbiosynthetic pathway. James Douglasdescribed his procedure for the prepa-ration of a number of thiobactomycinanalogs. Tests of their inhibiting activ-ities indicated which structural fea-tures were of value.

Samia Mezouari from MunsterUniversity in Germany is studying theformation of trans fatty acids. dimericglycerides, and particularly stigmasta-diene during processing. She foundthat deodorization at 200cC could pro-duce 0.2 mglkg stigmastadiene in sun-flower seed oil and 0.15 mg/kg inolive oil. However, the main effectswere in the bleaching step where 20minutes at 90°C resulted in some stig-mastadiene formation. The effects ofbleaching earth activity, time, andtemperature were investigated. Theuse of some additives could reducestigmastadiene levels. but could not bedisclosed at present.

Anne Marie Minihane of the Uni-versity of Reading is studying thenutritional effects of fish oil. Theblood lipid profile of about 20% of

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men is characterized by a hightriglyceride concentration. a reducedhigh-density lipoprotein (HDL)cholesterol level, and a high propor-tion of small, dense particles in theirlow-density lipoprotein (LOL). Sixtysubjects in a double-blind study withthis atherogenic lipoprotein pheno-type were given capsules containingeither 2.8 g eicosapenlaenoic acid ordocosahexaenoic acid, or olive oilfor 6-week periods with 12 weekswash-out in between. There was noeffect on total cholesterol levels oron glucose. Fasting blood triglyc-eride levels were 25-30% lower andpostprandial levels also werereduced. A next proposed step is tosee whether cr.-linolenic acid isequally effective.

K. Rakoski at the Queens Universi-ty. Belfast. is examining the use ofmicrobial lipase from Pseudomonasfor the industrial hydrolysis of fats.Potentially this could be less expen-sive in capital and operating costs. andsuitable for preparation of highlyunsaturated fatty acids.

The lipase was immobilized on asolid support consisting of porouspolypropylene. in some cases with15% added silica or chitosan. It wasfound that the water dissolved in thefat was sufficient to enable the reac-tion to proceed. During hydrolysis.water contents of 0.9-1.4% weredetermined. Hydrolysis was 98%complete in 24 hours.

Naomi Quinton is using facilitiesat both Sheffield Hallam Universityand the University of Sheffield in herstudy of obesity. The role of leptin insatiety regulation has aroused a greatdeal of interest, and is effectedthrough the presence of the leptinreceptors in the hypothalamus. Lep-tin receptors in other organs arethought to be involved in thermogen-esis, hematopoiesis. and reproduc-tion. Quinton measured leptin levelsin a sample population of post-menopausal women. She found goodcorrelation with body mass index(8M I). Several polymorphs of theleptin receptor are known. Quintonfound that womcn with two alleles ofthe G form of the gene had lowerserum levels of leptin than thosewith AA or with AG alleles. They

also had significantly lower BM!.Clearly. polymorphism of the leptinreceptor is a genetic factor in obesi-ty, and Quinton thinks this may bedue to differences in binding.

There were opportunities to exam-ine the three poster presentations dur-ing coffee and tea breaks and at lunchtime. Muhammed Dmar from Liver-pool John Moores Universitydescribed an eleven-step synthesis ofthe chiral methyl ester of 3-R-hydroxy-5-oxo-cyclopentene-l-hep-tanoic acid from methyl oleate. Themolecule is potentially of interest forits biological activity.

Keceli Turkan of Reading Univer-sity is investigating potential antimi-crobial activity of phenolics present inolive oil. At 50 ppm ryrosct. p-hydroxy phenylacetic acid. p-coumar-lc acid, and ferulic acid individuallyhad no effect on Streptococcus ther-mophilus or Lactobacillusbutgaricus-s-ei 200 ppm and above,the former was inhibited while the lat-ter was partly inhibited.

Matthew Hiscock from the Universi-ty of Newcastle showed his attempts tosynthesize diastereomeric lactones fromlong-chain 2-alkyl-3-hydroxy acids.

(Author's commelll: This reporterwas very impressed and mentallystretched by the wide range of topicspresented. Interaction between thestudents and the older members of theaudience of 30 was vigorous lind awelcome aspect of the meeting. Alsoimpressive was the general compe-tence of the presentations. especiallysince English was nOl the native lan-guage of several speakers. It II'(/S withconsiderable difficulty Ih(1/ the com·mittee chose Hazel Mottram to receivea small prize for the best presenta-tion.)

Lipid analysis discussedat Lipidforum seminar(This anicle is based on a report by80 Jorgensen of the Technical Uni-versity in Lyngby, Denmark. of theFeb. 2-3. 1998. Lipidforum seminarheld at that location.]

"Modern Methods of Lipid Analysis"was the theme of a Lipidforum semi-nar held earlier this year at the Techni-cal University in Lyngby, Denmark.which included 17 presentations infive sessions.

The opening session on extractionand sample preparation began with apresentation by Seren Bewadt fromVandkvalitetsinstituttet in Hershotm.Denmark. on using supercriticalfluid extraction for gravimetric fatdetermination. The system wasdescribed as faster than traditionalmethods. and it requires little, if any.organic solvent. Ingrid Undeland ofthe Swedish Food Institute in Gete-borg reported that the Bligh andDyer extraction method is stillamong the best available, but alter-native systems using detergent ratherthan chloroform may prove suitable.Lea Hyvcnen of Helsinki Universityin Finland concluded that extractedfatty acids expressed as triacylglyc-erol equivalents provide a more use-ful description of the nutritionallyrelevant energy content than does asum total of extracted "fat," whichcan include nonfat materials.

In a session on spectroscopy anddata analysis, Marit Aursand of SIN-TEF in Trondheim, Norway. dis-cussed the advantages of using non-destructive, noninvasive nuclearmagnetic resonance techniques forlipids in biological and food sam-ples. W.w. Christie of the ScottishCrop Research Institute in Dundee,Scotland, covered use of gas chro-matography-mass spectroscopy forstructure determination. Peter Kauf-mann of Scotia LipidTeknik inStockholm. Sweden, spoke on usingchemometrics in design, develop-ment. and validation of analyticalmethods. Chemometrics' use as aclassification tool was covered byTorben Leth from veterinar og Fade-vare Direktoratet in Seborg. Den-mark. Loui Larsen of Perkin-Elmerin Allered, Denmark, discussed thehandling of chromatographic data indesktop computers and network sys-tems.

The third session covered liquidand gas chromatography, withChristie opening the program with atalk on silver-ion chromatography.

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MEETINGS

fatty acid composition in marineoils."

Supercrhical chromatography wasthe topic for the fourth session. withChristine Botch-Jensen of the Tech-nical University in Lyngby. Den-mark, beginning the program byshowing some possible applications.including separations at lower tem-peratures for unstable compoundssuch as polyunsaturated acyl groups.Kim G. Stjerne of Biolab/Arhus inDenmark spoke on separation oftriglyceride classes using supercriti-cal chromatography.

The final session was an overviewof international standards methods byKarsten Stig Andersen of AarhusOils & Fats AIS. Denmark. One

major concern has been the relativelylengthy time required for new merh-ods (0 be approved by internationalgroups.

The seminar, which included aseminar dinner, attracted 77 partici-pants. The official seminar bookletcontaining the program, list of par-ticipants, and abstracts of almost allthe presentations and poster is avail-able from the Lipidforum SecretaryIclo E.N. Christiansen, Institute forNutrition Research. P.O. Box 1046,Blindern, N-03l6 Oslo, Norway(phone: 47-22-851357; fax: 47-22-851341; e-mail:[email protected]). Thecost is 120 NOK (Norwegian krone)($16), which includes postage. •

Anu Hopia of Helsinki Universityspoke on using high-performanceliquid chromatography (HPLC) witha combination of detectors that canprovide details of primary oxidationproducts. Yves Dehan of Hewlett-Packard in Birkered. Denmark. andCraig Dorschel of Waters in Mil-ford, Massachusetts, each gave atalk on using a mass spectrometer asan HPLC detector. Carl-Erik Hay ofthe Technical University in Lyngby,Denmark. discussed analysis ofintere s terified fats, a topic ofincreasing importance. The finalpresentation in the session, by TerjeAasoldsen of Perkin-Elmer in Oslo,Norway, was a demonstration of a"Standard fish oil analysator for

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