- 1. Modern Food MicrobiologySixth EditionJames M. JayProfessor
EmeritusWayne State UniversityDetroit, MichiganAdjunct
ProfessorUniversity of Nevada Las VegasLas Vegas, NevadaAN ASPEN
PUBLICATIONAspen Publishers, Inc.Gaithersburg, Maryland2000
2. The author has made every effort to ensure the accuracy of
the information herein. However, appropriate informationsources
should be consulted. The author, editors, and the publisher cannot
be held responsible for any typographical orother errors found in
this book.Library of Congress Cataloging-in-Publication DataJay,
James M. (James Monroe), 1927Modern food microbiology / James M.
Jay.6th ed.p. cm. (Aspen food science text series)Includes
bibliographical references and index.ISBN 0-8342-1671-X1.
FoodMicrobiology. I. Title. II. Series.QR115.J3
2000664'001'579dc2199-054735Copyright O 2000 by Aspen Publishers,
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in the United States of America2 3 4 5 3. PrefaceThe sixth edition
of Modern Food Microbiol-ogy,like the previous edition, focuses on
thegeneral biology of the microorganisms that arefound in foods.
Thus, the contents are suitablefor its use in a second or
subsequent course in amicrobiology curriculum, or as a primary
foodmicrobiology course in a food science or foodtechnology
curriculum. Although organic chem-istryis a desirable prerequisite,
it is not neces-saryfor one to get a good grasp of the
topicscovered.When used as a microbiology text, the
fol-lowingsequence has been found to be suitable.A synopsis of the
information in Chapter 1 willprovide students with a sense of the
historicaldevelopments that have shaped this disciplineand how it
continues to evolve. Memorizationof the many dates and events is
not recommendedsince much of this information is presented againin
the respective chapters. The material in Chap-ter2 is designed to
provide a brief backgroundon microorganisms in nature with emphasis
onthose that are important in foods. This materialcan be combined
with the intrinsic and extrinsicparameters of growth in Chapter 3
as they existin food products and as they affect the
commonfoodborne organisms. Chapters 4 to 9 deal withspecific food
products and they may be coveredto the extent desired with
appropriate reviews ofthe relevant topics in Chapter 3. Chapters 10
to12 cover methods for culturing and identifyingfoodborne organisms
and/or their products, andthese topics may be dealt with in this
sequenceor just before foodborne pathogens. The foodpreservation
methods in Chapters 13 to 19 in-cludeinformation that goes beyond
the usualscope of a second course. Chapters 14 and 19are new to the
sixth edition. Chapter 14 consoli-datesinformation from the
previous edition thatwas scattered throughout several chapters,
andit contains much new information on modifiedatmosphere
packaging. Chapter 19 covers highpressure and pulsed electric field
processing offoods, and it contains two sections taken fromthe
chapter on high temperature processing inthe previous
edition.Chapters 20 and 21 deal with food sanitation,indicator
organisms, and the HACCP system, andcoverage of these topics is
suggested before deal-ingwith the pathogens. Chapters 22 to 31
dealwith the known (and some suspected) foodbornepathogens
including their biology and methodsof control. Chapter 22 is also
new to this edi-tionand it is intended to provide an overview ofthe
chapters that follow. The material in this chap-terthat deals with
mechanisms of pathogenesisis probably best dealt with when the
specificpathogens are covered in their respective chap-ters.For
most semester courses with a 3-credit lec-tureand accompanying 2 or
3 credit laboratory,only about 70% of the material in this edition
is 4. likely to be covered. The remainder is meant forreference
purposes. Citations for new and up-datedmaterial can be found in
the Reference listsat the end of the chapters.The following
individuals assisted me bycritiquing various parts or sections of
the sixthedition, and I pay my special thanks to each:P. Druggan,
P. Feng, R.B. Gravani, D.R. Henning,YJ. Lee, J.A. Seiter, L.A.
Shelef, J.N. Sofos,A.C.L. Wong, and A.E. Yousef. Those who
as-sistedme with the previous five editions are ac-knowledgedin the
respective editions. 5. This page has been reformatted by Knovel to
provide easier navigation. vContentsPreface
....................................................................................................
xvPart I. Historical Background
.............................................................. 11.
History of Microorganisms in Food
..........................................................
3Historical Developments
...................................................................
4Part II. Habitats, Taxonomy, and Growth Parameters
....................... 112. Taxonomy, Role, and Significance of
Microorganisms in Foods ............ 13Bacterial Taxonomy
..........................................................................
13Primary Sources of Microorganisms Found in Foods
........................ 17Synopsis of Common Foodborne Bacteria
....................................... 19Synopsis of Common Genera
of Foodborne Molds .......................... 24Synopsis of Common
Genera of Foodborne Yeasts ......................... 293. Intrinsic
and Extrinsic Parameters of Foods That Affect MicrobialGrowth
.....................................................................................................
35Intrinsic Parameters
.........................................................................
35Extrinsic Parameters
........................................................................
49Combined Intrinsic and Extrinsic Parameters: The HurdleConcept
......................................................................................
53Part III. Microorganisms in Foods
...................................................... 574. Fresh
Meats and Poultry
.........................................................................
59Biochemical Events That Lead to Rigor Mortis
................................. 60The Biota of Meats and Poultry
........................................................
60Incidence/Prevalence of Microorganisms in Fresh Red Meats
.......... 60Microbial Spoilage of Fresh Red Meats
............................................ 68Spoilage of Fresh
Livers
...................................................................
76Incidence/Prevalence of Microorganisms in Fresh Poultry
................ 77Microbial Spoilage of Poultry
............................................................
78Carcass Sanitizing/Washing
............................................................. 81 6.
vi Contents5. Processed Meats
.....................................................................................
87Curing
..............................................................................................
87Smoking
...........................................................................................
89Sausage, Bacon, Bologna, and Related Products
............................ 89Bacon and Cured Hams
...................................................................
91Fermented Meat Products
................................................................
936. Seafoods
..................................................................................................
101Microbiological Quality of Various Fresh and Frozen Products
......... 101Fermented Fish Products
.................................................................
104Spoilage of Fish and Shellfish
.......................................................... 1057.
Fermentation and Fermented Dairy Products
......................................... 113Fermentation
....................................................................................
113Dairy Products
..................................................................................
119Apparent Health Benefits of Fermented Milks
................................... 124Diseases Caused by Lactic
Acid Bacteria ......................................... 1288. Fruit
and Vegetable Products: Whole, Fresh-Cut, andFermented
................................................................................................
131Fresh and Frozen Vegetables
..........................................................
131Spoilage of Fruits
.............................................................................
141Fresh-Cut Produce
...........................................................................
141Fermented Products
.........................................................................
146Miscellaneous Fermented Products
.................................................. 1549.
Miscellaneous Food Products
.................................................................
163Delicatessen and Related Foods
...................................................... 163Eggs
.................................................................................................
164Mayonnaise and Salad Dressing
...................................................... 167Cereals,
Flour, and Dough Products
................................................. 168Bakery
Products
...............................................................................
168Frozen Meat Pies
.............................................................................
168Sugar, Candies, and Spices
.............................................................
169Nutmeats
..........................................................................................
169Dehydrated Foods
............................................................................
170Enteral Nutrient Solutions (Medical Foods)
....................................... 171Single-Cell Protein
............................................................................
171This page has been reformatted by Knovel to provide easier
navigation. 7. Contents viiPart IV. Determining Microorganisms
and/or Their Products inFoods
........................................................................................
17710. Culture, Microscopic, and Sampling Methods
........................................ 179Conventional Standard
Plate Count ..................................................
179Membrane Filters
.............................................................................
182Microscope Colony Counts
...............................................................
184Agar Droplets
...................................................................................
184Dry Film and Related Methods
......................................................... 185Most
Probable Numbers
...................................................................
186Dye Reduction
..................................................................................
186Roll Tubes
........................................................................................
187Direct Microscopic Count
..................................................................
187Microbiological Examination of Surfaces
.......................................... 188Metabolically Injured
Organisms .......................................................
190Viable but Nonculturable Organisms
................................................ 19411. Physical,
Chemical, Molecular, and Immunological Methods ................
201Physical Methods
.............................................................................
201Chemical Methods
............................................................................
206Methods for Characterizing and Fingerprinting FoodborneOrganisms
..................................................................................
214Immunological Methods
....................................................................
22112. Bioassay and Related Methods
..............................................................
237Whole-Animal Assays
.......................................................................
237Animal Models Requiring Surgical Procedures
................................. 242Cell Culture Systems
........................................................................
243Part V. Food Preservation and Some Properties ofPsychrotrophs,
Thermophiles, and Radiation-ResistantBacteria
.....................................................................................
25113. Food Preservation with Chemicals
..........................................................
253Benzoic Acid and the Parabens
........................................................ 253Sorbic
Acid
.......................................................................................
255The Propionates
...............................................................................
257Sulfur Dioxide and Sulfites
...............................................................
257This page has been reformatted by Knovel to provide easier
navigation. 8. viii ContentsNitrites and Nitrates
..........................................................................
258NaCl and Sugars
..............................................................................
264Indirect Antimicrobials
......................................................................
265Acetic and Lactic Acids
.....................................................................
268Antibiotics and Bacteriocins
..............................................................
268Antifungal Agents for Fruits
..............................................................
274Ethylene and Propylene Oxides
.......................................................
274Miscellaneous Chemical Preservatives
............................................. 27514. Food
Preservation with Modified Atmospheres
...................................... 283Definitions
........................................................................................
283Primary Effects of CO2 on Microorganisms
....................................... 286Food Products
..................................................................................
288The Safety of MAP Foods
.................................................................
290Spoilage of MAP and Vacuum-Packaged Meats
.............................. 29315. Radiation Preservation of
Foods and Nature of MicrobialRadiation Resistance
...............................................................................
301Characteristics of Radiations of Interest in Food Preservation
.......... 301Principles Underlying the Destruction of
Microorganisms byIrradiation
...................................................................................
303Processing of Foods for Irradiation
................................................... 305Application
of Radiation
....................................................................
305Radappertization, Radicidation, and Radurization of Foods
............. 306Legal Status of Food Irradiation
........................................................ 312Effect
of Irradiation on Food Quality
................................................. 313Storage
Stability of Irradiated Foods
................................................. 315Nature of
Radiation Resistance of Microorganisms ..........................
31516. Low-Temperature Food Preservation and Characteristics
ofPsychrotrophic Microorganisms
..............................................................
323Definitions
........................................................................................
323Temperature Growth Minima
............................................................
324Preparation of Foods for Freezing
.................................................... 324Freezing of
Foods and Freezing Effects
........................................... 325Storage Stability of
Frozen Foods ....................................................
327This page has been reformatted by Knovel to provide easier
navigation. 9. Contents ixEffect of Freezing on Microorganisms
.............................................. 327Some
Characteristics of Psychrotrophs and Psychrophiles ..............
331The Effect of Low Temperatures on Microbial
PhysiologicMechanisms
...............................................................................
333Nature of the Low Heat Resistance of Psychrotrophs
....................... 33617. High-Temperature Food Preservation
and Characteristics ofThermophilic Microorganisms
.................................................................
341Factors Affecting Heat Resistance in Microorganisms
...................... 342Relative Heat Resistance of
Microorganisms ................................... 346Thermal
Destruction of Microorganisms
........................................... 348Some Characteristics
of Thermophiles .............................................
351Other Aspects of Thermophilic Microorganisms
................................ 354Canned Food Spoilage
.....................................................................
35618. Preservation of Foods by Drying
.............................................................
363Preparation and Drying of Low-Moisture Foods
................................ 363Effect of Drying on
Microorganisms ..................................................
364Storage Stability of Dried Foods
.......................................................
366Intermediate-Moisture Foods
............................................................ 36719.
Other Food Preservation Methods
..........................................................
375High-Pressure Processing
................................................................
375Pulsed Electric Fields
.......................................................................
379Aseptic Packaging
............................................................................
380Manothermosonication (Thermoultrasonication)
............................... 381Part VI. Indicators of Food
Safety and Quality, Principles ofQuality Control, and Microbial
Criteria ................................... 38520. Indicators of
Food Microbial Quality and Safety
..................................... 387Indicators of Product
Quality
............................................................
387Indicators of Food Safety
..................................................................
388The Possible Overuse of Fecal Indicator Organisms
........................ 401Predictive Microbiology/Microbial
Modeling ...................................... 40221. The HACCP
System and Food Safety
.................................................... 407Hazard
Analysis Critical Control Point System
................................. 407Microbiological Criteria
.....................................................................
415This page has been reformatted by Knovel to provide easier
navigation. 10. x ContentsPart VII. Foodborne Diseases
..............................................................
42322. Introduction to Foodborne Pathogens
.....................................................
425Introduction
......................................................................................
425Host Invasion
...................................................................................
425Pathogenesis
....................................................................................
428Summary
..........................................................................................
43423. Staphylococcal Gastroenteritis
................................................................
441Species of Concern in Foods
............................................................
441Habitat and Distribution
....................................................................
443Incidence in Foods
...........................................................................
443Nutritional Requirements for Growth
................................................. 444Temperature
Growth Range
.............................................................
444Effect of Salts and Other Chemicals
................................................. 444Effect of pH,
Water Activity, and Other Parameters ..........................
444Staphylococcal Enterotoxins: Types and Incidence
.......................... 445The Gastroenteritis Syndrome
..........................................................
453Incidence and Vehicle Foods
............................................................
454Ecology of S. aureus Growth
............................................................
455Prevention of Staphylococcal and Other Food-PoisoningSyndromes
.................................................................................
45524. Food Poisoning Caused by Gram-Positive SporeformingBacteria
....................................................................................................
461Clostridium perfringens Food Poisoning
........................................... 461Botulism
...........................................................................................
466Bacillus Cereus Gastroenteritis
........................................................ 47725.
Foodborne Listeriosis
..............................................................................
485Taxonomy of Listeria
........................................................................
485Growth
..............................................................................................
488Distribution
.......................................................................................
492Thermal Properties
...........................................................................
494Virulence Properties
.........................................................................
497Animal Models and Infectious Dose
.................................................. 498Incidence and
Nature of the Listeriosis Syndromes ..........................
500Resistance to Listeriosis
...................................................................
502This page has been reformatted by Knovel to provide easier
navigation. 11. Contents xiPersistence of L. monocytogenes in Foods
...................................... 503Regulatory Status of L.
monocytogenes in Foods ............................. 50426.
Foodborne Gastroenteritis Caused by Salmonella and Shigella
............ 511Salmonellosis
...................................................................................
511Shigellosis
........................................................................................
52527. Foodborne Gastroenteritis Caused by Escherichia coli
.......................... 531Serological Classification
..................................................................
531The Recognized Virulence Groups
................................................... 531Prevention
........................................................................................
543Travelers' Diarrhea
...........................................................................
54328. Foodborne Gastroenteritis Caused by Vibrio, Yersinia,
andCampylobacter Species
...........................................................................
549Vibriosis (Vibrio parahaemolyticus )
.................................................. 549Other Vibrios
....................................................................................
552Yersiniosis (Yersinia enterocolitica)
..................................................
556Campylobacteriosis (Campylobacter jejuni)
...................................... 560Prevention
........................................................................................
56329. Foodborne Animal Parasites
...................................................................
569Protozoa
...........................................................................................
569Flatworms
.........................................................................................
579Roundworms
....................................................................................
58430. Mycotoxins
...............................................................................................
595Aflatoxins
..........................................................................................
595Alternaria Toxins
..............................................................................
600Citrinin
..............................................................................................
600Ochratoxins
......................................................................................
601Patulin
..............................................................................................
601Penicillic Acid
....................................................................................
602Sterigmatocystin
...............................................................................
602Fumonisins
.......................................................................................
602Sambutoxin
......................................................................................
606Zearalenone
.....................................................................................
606Control of Production
........................................................................
606This page has been reformatted by Knovel to provide easier
navigation. 12. xii Contents31. Viruses and Some Other Proven and
Suspected FoodborneBiohazards
...............................................................................................
611Viruses
.............................................................................................
611Bacteria and Prions
..........................................................................
616Toxigenic Phytoplanktons
.................................................................
622Appendices
............................................................................................
629Appendix A: Relationships of Common Foodborne Genera of
Gram-Negative Bacteria
....................................................................................
629Appendix B: Relationship of Common Foodborne Genera of
Gram-Positive Bacteria
......................................................................................
631Appendix C: Biofilms
......................................................................................
633Appendix D: Grouping of the Gram-Negative Asporogenous
Rods,Polar-Flagellate, Oxidase Positive, and Not Sensitive to 2.5
IUPenicillin, on the Results of Four Other Tests
......................................... 635Index
.......................................................................................................
637This page has been reformatted by Knovel to provide easier
navigation. 13. PART IHistorical BackgroundThe material in this
part provides a glimpseof some of the early events that ultimately
led tothe recognition of the significance and role ofmicroorganisms
in foods. Food microbiology asa defined subdiscipline does not have
a precisebeginning. Some of the early findings and ob-servationsare
noted, along with dates. The se-lectivelists of events noted for
food preserva-tion,food spoilage, food poisoning, and
foodlegislation are meant to be guideposts in the
con-tinuingevolution and development of food mi-crobiology.An
excellent and more detailed review of thehistory of food
microbiology has been presentedby Hartman.Hartman, P.A. 1997. The
evolution of food microbiology.In Food MicrobiologyFundamentals and
Frontiers,eds. M.P Doyle, L.R. Beuchat, and TJ. Montville,
3-12.Washington, D.C.: ASM Press. 14. CHAPTER 1History of
Microorganisms in FoodAlthough it is extremely difficult to
pinpointthe precise beginnings of human awareness ofthe presence
and role of microorganisms infoods, the available evidence
indicates that thisknowledge preceded the establishment of
bacte-riologyor microbiology as a science. The eraprior to the
establishment of bacteriology as ascience may be designated the
prescientific era.This era may be further divided into what hasbeen
called the food-gathering period and thefood-producing period. The
former covers thetime from human origin over 1 million years agoup
to 8,000 years ago. During this period, hu-manswere presumably
carnivorous, with plantfoods coming into their diet later in this
period.It is also during this period that foods were
firstcooked.The food-producing period dates from about8,000 to
10,000 years ago and, of course, includesthe present time. It is
presumed that the prob-lemsof spoilage and food poisoning were
en-counteredearly in this period. With the adventof prepared foods,
the problems of disease trans-missionby foods and of faster
spoilage causedby improper storage made their appearance.Spoilage
of prepared foods apparently dates fromaround 6000 BC. The practice
of making potterywas brought to Western Europe about 5000 BCfrom
the Near East. The first boiler pots arethought to have originated
in the Near East about8,000 years ago.11 The arts of cereal
cookery,brewing, and food storage were either started atabout this
time or stimulated by this new devel-opment.10 The first evidence
of beer manufac-turehas been traced to ancient Babylonia as farback
as 7000 BC.8 The Sumerians of about 3000BC are believed to have
been the first great live-stockbreeders and dairymen and were
amongthe first to make butter. Salted meats, fish, fat,dried skins,
wheat, and barley are also known tohave been associated with this
culture. Milk,butter, and cheese were used by the Egyptians asearly
as 3000 BC. Between 3000 BC and 1200 BC,the Jews used salt from the
Dead Sea in the pres-ervationof various foods.2 The Chinese
andGreeks used salted fish in their diet, and theGreeks are
credited with passing this practice onto the Romans, whose diet
included pickledmeats. Mummification and preservation of foodswere
related technologies that seem to have in-fluencedeach other's
development. Wines areknown to have been prepared by the
Assyriansby 3500 BC. Fermented sausages were preparedand consumed
by the ancient Babyloniansand the people of ancient China as far
back as1500 BC.8Another method of food preservation that
ap-parentlyarose during this time was the use ofoils such as olive
and sesame. Jensen7 has pointedout that the use of oils leads to
high incidencesof staphylococcal food poisoning. The Romansexcelled
in the preservation of meats other thanbeef by around 1000 BC and
are known to haveused snow to pack prawns and other perishables,
15. according to Seneca. The practice of smokingmeats as a form of
preservation is presumed tohave emerged sometime during this
period, asdid the making of cheese and wines. It is
doubt-fulwhether people at this time understood thenature of these
newly found preservation tech-niques.It is also doubtful whether
the role offoods in the transmission of disease or the dan-gerof
eating meat from infected animals wasrecognized.Few advances were
apparently made towardunderstanding the nature of food poisoning
andfood spoilage between the time of the birth ofChrist and AD
1100. Ergot poisoning (caused byClaviceps purpurea, a fungus that
grows on ryeand other grains) caused many deaths during theMiddle
Ages. Over 40,000 deaths due to ergotpoisoning were recorded in
France alone in AD943, but it was not known that the toxin of
thisdisease was produced by a fungus.12 Meat butch-ersare mentioned
for the first time in 1156, andby 1248 the Swiss were concerned
with market-ableand nonmarketable meats. In 1276, a
com-pulsoryslaughter and inspection order was is-suedfor public
abattoirs in Augsburg. Althoughpeople were aware of quality
attributes in meatsby the thirteenth century, it is doubtful that
therewas any knowledge of the causal relationshipbetween meat
quality and microorganisms.Perhaps the first person to suggest the
role ofmicroorganisms in spoiling foods was A. Kircher,a monk, who
as early as 1658 examined decay-ingbodies, meat, milk, and other
substances andsaw what he referred to as "worms" invisible tothe
naked eye. Kircher's descriptions lacked pre-cision,however, and
his observations did not re-ceivewide acceptance. In 1765, L.
Spallanzanishowed that beef broth that had been boiled foran hour
and sealed remained sterile and did notspoil. Spallanzani performed
this experiment todisprove the doctrine of the spontaneous
gen-erationof life. However, he did not convince theproponents of
the theory because they believedthat his treatment excluded oxygen,
which theyfelt was vital to spontaneous generation. In 1837,Schwann
showed that heated infusions remainedsterile in the presence of
air, which he suppliedby passing it through heated coils into the
infu-sion.9 Although both of these men demonstratedthe idea of the
heat preservation of foods, nei-thertook advantage of his findings
with respectto application. The same may be said of D. Papinand G.
Leibniz, who hinted at the heat preserva-tionof foods at the turn
of the eighteenth cen-tury.The event that led to the discovery of
canninghad its beginnings in 1795, when the Frenchgovernment
offered a prize of 12,000 francs forthe discovery of a practical
method of food pres-ervation.In 1809, a Parisian
confectioner,Frangois (Nicholas) Appert, succeeded in
pre-servingmeats in glass bottles that had been keptin boiling
water for varying periods of time. Thisdiscovery was made public in
1810, when Appertwas issued a patent for his process.6 Not being
ascientist, Appert was probably unaware of thelong-range
significance of his discovery or whyit worked. This, of course, was
the beginning ofcanning as it is known and practiced today.5
Thisevent occurred some 50 years before L. Pasteurdemonstrated the
role of microorganisms in thespoilage of French wines, a
development thatgave rise to the rediscovery of bacteria.
A.Leeuwenhoek in the Netherlands had examinedbacteria through a
microscope and describedthem in 1683, but it is unlikely that
Appert wasaware of this development, as he was not a sci-entistand
Leeuwenhoek's report was not avail-ablein French.The first person
to appreciate and understandthe presence and role of microorganisms
in foodwas Pasteur. In 1837, he showed that the souringof milk was
caused by microorganisms, and inabout 1860 he used heat for the
first time to de-stroyundesirable organisms in wine and beer.This
process is now known as pasteurization.HISTORICAL DEVELOPMENTSSome
of the more significant dates and eventsin the history of food
preservation, food spoil- 16. age, food poisoning, and food
legislation arelisted below.Food Preservation1782 Canning of
vinegar was introduced by aSwedish chemist.1810Preservation of food
by canning waspatented by Appert in France. Peter Durand was issued
a British patentto preserve food in "glass, pottery, tinor other
metals or fit materials." Thepatent was later acquired by
Hall,Gamble, and Donkin, possibly fromAppert.141813Donkin, Hall,
and Gamble introducedthe practice of postprocessing incubationof
canned foods. Use of SO2 as a meat preservative isthought to have
originated around thistime.1825T. Kensett and E. Daggett were
granteda U.S. patent for preserving food in tincans.1835A patent
was granted to Newton in En-glandfor making condensed
milk.1837Winslow was the first to can corn fromthe cob.1839Tin cans
came into wide use in theUnited States.3 L.A. Fastier was given a
French patentfor the use of brine bath to raise the
boil-ingtemperature of water.1840 Fish and fruit were first
canned.1841S. Goldner and J. Wertheimer were is-suedBritish patents
for brine baths basedon Fastier's method.1842A patent was issued to
H. Benjamin inEngland for freezing foods by immer-sionin an ice and
salt brine.1843Sterilization by steam was first at-temptedby I.
Winslow in Maine.1845 S. Elliott introduced canning to
Austra-lia.1853R. Chevallier-Appert obtained a patentfor
sterilization of food by autoclaving.1854 Pasteur began wine
investigations. Heat-ingto remove undesirable organismswas
introduced commercially in 1867-1868.1855Grim wade in England was
the first toproduce powdered milk.1856 A patent for the manufacture
of unsweet-enedcondensed milk was granted to GailBorden in the
United States,1861 I. Solomon introduced the use of brinebaths to
the United States.1865The artificial freezing offish on a
com-mercialscale was begun in the UnitedStates. Eggs followed in
1889.1874The first extensive use of ice in trans-portingmeat at sea
was begun. Steam pressure cookers or retorts wereintroduced.1878
The first successful cargo of frozen meatwent from Australia to
England. The firstfrom New Zealand to England was sentin 1882.1880
The pasteurization of milk was begun inGermany.1882Krukowitsch was
the first to note thedestructive effects of ozone on
spoilagebacteria.1886A mechanical process of drying fruitsand
vegetables was carried out by anAmerican, A.F. Spawn.1890The
commercial pasteurization of milkwas begun in the United States.
Mechanical refrigeration for fruit stor-agewas begun in
Chicago.1893The Certified Milk movement was be-gunby H.L. Coit in
New Jersey.1895The first bacteriological study of can-ningwas made
by Russell.1907E. Metchnikoff and co-workers isolatedand named one
of the yogurt bacteria,Lactobacillus bulgaricus. The role of acetic
acid bacteria in ciderproduction was noted by B.TP.
Barker.1908Sodium benzoate was given officialsanction by the United
States as a pre-servativein certain foods. 17. 1916The quick
freezing of foods wasachieved in Germany by R. Plank, E.Ehrenbaum,
and K. Reuter.1917Clarence Birdseye in the United Statesbegan work
on the freezing of foods forthe retail trade. Franks was issued a
patent for preserv-ingfruits and vegetables under CO2.1920Bigelow
and Esty published the firstsystematic study of spore heat
resistanceabove 212F. The "general method" forcalculating thermal
processes was pub-lishedby Bigelow, Bohart, Richardson,and Ball;
the method was simplified byCO. Ball in 1923.1922 Esty and Meyer
establishedz = 18F forClostridium botulinum spores in
phos-phatebuffer.1928The first commercial use of
controlled-atmospherestorage of apples was madein Europe (first
used in New York in1940).1929A patent issued in France proposed
theuse of high-energy radiation for the pro-cessingof foods.
Birdseye frozen foods were placed inretail markets.1943 B.E.
Proctor in the United States was thefirst to employ the use of
ionizing ra-diationto preserve hamburger meat.1950The D value
concept came into generaluse.1954 The antibiotic nisin was patented
in En-glandfor use in certain processedcheeses to control
clostridial defects,1955Sorbic acid was approved for use as afood
preservative. The antibiotic chlortetracycline was ap-provedfor use
in fresh poultry (oxytet-racyclinefollowed a year later).
Ap-provalwas rescinded in 1966.1967The first commercial facility
designedto irradiate foods was planned anddesigned in the United
States. The sec-ondbecame operational in 1992 inFlorida.1988Nisin
accorded GRAS (generally re-gardedas safe) status in the
UnitedStates.1990Irradiation of poultry approved in theUnited
States.1997The irradiation of fresh beef up to amaximum level of
4.5 kGy and frozenbeef up to 7.0 kGy was approved in theUnited
States.1997Ozone was declared GRAS by the U.S.Food and Drug
Administration for fooduse.Food Spoilage1659 Kircher demonstrated
the occurrence ofbacteria in milk; Bondeau did the samein
1847.1680Leeuwenhoek was the first to observeyeast cells.1780
Scheele identified lactic acid as the prin-cipalacid in sour
milk.1836Latour discovered the existence ofyeasts.1839Kircher
examined slimy beet juice andfound organisms that formed slime
whengrown in sucrose solutions.1857 Pasteur showed that the souring
of milkwas caused by the growth of organismsin it.1866 L. Pasteur's
Etude sur Ie Vin was pub-lished.1867Martin advanced the theory that
cheeseripening was similar to alcoholic, lactic,and butyric
fermentations.1873The first reported study on the
micro-bialdeterioration of eggs was carried outby Gayon. Lister was
first to isolate Lactococcuslactis in pure culture.1876 Tyndall
observed that bacteria in decom-posingsubstances were always
traceableto air, substances, or containers.1878Cienkowski reported
the first micro-biologicalstudy of sugar slimes and 18. isolated
Leuconostoc mesenteroidesfrom them.1887Forster was the first to
demonstrate theability of pure cultures of bacteria togrow at
00C.1888Miquel was the first to study thermo-philicbacteria.1895The
first records on the determinationof numbers of bacteria in milk
werethose of Von Geuns in Amsterdam. S.C. Prescott and W. Underwood
tracedthe spoilage of canned corn to improperheat processing for
the first time.1902 The termpsychrophile was first used
bySchmidt-Nielsen for microorganismsthat grow at 00C.1912The term
osmophilic was coined byRichter to describe yeasts that grow wellin
an environment of high osmotic pres-sure.1915Bacillus coagulans was
first isolatedfrom coagulated milk by B. W. Hammer.1917Bacillus
stearothermophilus was firstisolated from cream-style corn by
RJ.Donk.1933Oliver and Smith in England observedspoilage by
Byssochlamys fulva; firstdescribed in the United States in 1964by
D. Maunder.Food Poisoning1820The German poet Justinus Kerner
de-scribed"sausage poisoning" (which inall probability was
botulism) and its highfatality rate.1857Milk was incriminated as a
transmitterof typhoid fever by W. Taylor of Penrith,England.1870
Francesco Selmi advanced his theory ofptomaine poisoning to explain
illnesscontracted by eating certain foods.1888 Gaertner first
isolated Salmonella enter-itidisfrom meat that had caused 57
casesof food poisoning.1894T. Denys was the first to
associatestaphylococci with food poisoning.1896Van Ermengem first
discoveredClostridium botulinum.1904Type A strain of C. botulinum
was iden-tifiedby G. Landman.1906 Bacillus cereus food poisoning
was rec-ognized.The first case of diphylloboth-riasiswas
recognized.1926 The first report of food poisoning bystreptococci
was made by Linden,Turner, and Thorn.1937Type E strain of C.
botulinum was iden-tifiedby L. Bier and E. Hazen.1937 Paralytic
shellfish poisoning was recog-nized.1938Outbreaks of Campylobacter
enteritiswere traced to milk in Illinois.1939Gastroenteritis caused
by Yersiniaenterocolitica was first recognized bySchleifstein and
Coleman.1945 McClung was the first to prove the etio-logicstatus of
Clostridium perfringens(welchii) in food poisoning.1951 Vibrio
parahaemolyticus was shown tobe an agent of food poisoning by
T.Fujino of Japan.1955Similarities between cholera and
Es-cherichiacoli gastroenteritis in infantswere noted by S.
Thompson. Scombroid (histamine-associated) poi-soningwas
recognized. The first documented case of anisakiasisoccurred in the
United States.1960Type F strain of C. botulinum identifiedby Moller
and Scheibel. The production of aflatoxins by As-pergillusflavus
was first reported.1965Foodborne giardiasis was recognized.1969 C.
perfringens enterotoxin was demon-stratedby CL. Duncan and D.H.
Strong. C. botulinum type G was first isolatedin Argentina by
Gimenez and Ciccarelli.1971 First U.S. foodborne outbreak of
Vibriopar ahaemolyticus gastroenteritis oc-curredin Maryland. 19.
First documented outbreak of E. colifoodborne gastroenteritis
occurred in theUnited States.1975Salmonella enterotoxin was
demon-stratedby L.R. Koupal and R.H. Deibel.1976 First U.S.
foodborne outbreak of Yersiniaenterocolitica gastroenteritis
occurred inNew York. Infant botulism was first recognized
inCalifornia.1977The first documented outbreak ofcyclosporiasis
occurred in Papua, NewGuinea; first in United States in 1990.1978
Documented foodborne outbreak of gas-troenteritiscaused by the
Norwalk virusoccurred in Australia.1979Foodborne gastroenteritis
caused bynon-01 Vibrio cholerae occurred in Flor-ida.Earlier
outbreaks occurred in Czecho-slovakia(1965) and Australia
(1973).1981 Foodborne listeriosis outbreak was rec-ognizedin the
United States.1982The first outbreaks of foodborne
hem-orrhagiccolitis occurred in the UnitedStates.1983Campylobacter
jejuni enterotoxin wasdescribed by Ruiz-Palacios et al.1985 The
irradiation of pork to 0.3 to 1.0 kGyto control Trichinella
spiralis was ap-provedin the United States.1986Bovine spongiform
encephalopathy(BSE) was first diagnosed in cattle inthe United
Kingdom.Food Legislation1890The first national meat inspection
lawwas enacted. It required the inspectionof meats for export
only.REFERENCES1. Bishop, RW. 1978. Who introduced the tin can?
NicolasAppert? Peter Durand? Bryan Donkin? Food
Technol32(4):60-67.2. Brandly, RJ., G. Migaki, and K.E. Taylor,
1966. MeatHygiene. 3d ed., Chap. 1. Philadelphia: Lea &
Febiger.1895The previous meat inspection actwas amended to
strengthen its provi-sions.1906 The U.S. Federal Food and Drug Act
waspassed by Congress.1910The New York City Board of Health
is-suedan order requiring the pasteuriza-tionof milk.1939 The new
Food, Drug, and Cosmetic Actbecame law.1954 The Miller Pesticide
Chemicals Amend-mentto the Food, Drug, and CosmeticAct was passed
by Congress.1957 The U.S. Compulsory Poultry and Poul-tryProducts
law was enacted.1958The Food Additives Amendment to theFood Drug,
and Cosmetics Act waspassed.1962The Talmadge-Aiken Act (allowing
forfederal meat inspection by states) wasenacted into law.1963 The
U.S. Food and Drug Administrationapproved the use of irradiation
for thepreservation of bacon.1967The U.S. Wholesome Meat Act
waspassed by Congress and enacted into lawon December 15.1968 The
Food and Drug Administration with-drewits 1963 approval of
irradiated ba-con. The Poultry Inspection Bill was signedinto
law.1969The U.S. Food and Drug Administra-tionestablished an
allowable level of20 ppb of aflatoxin for edible grains
andnuts.1973The state of Oregon adopted microbialstandards for
fresh and processed retailmeat. They were repealed in 1977.3.
Cowell, N.D. 1995. Who introduced the tin can?Anew candidate. Food
Technol 49(12):61-64.4. Farrer, K.T.H. 1979. Who invented the
brinebath?The Isaac Solomon myth. Food Technol. 33(2):75-77. 20. 5.
Goldblith, S. A. 1971. A condensed history of the sci-enceand
technology of thermal processing. FoodTechnol. 25(12): 44-50.6.
Goldblith, S.A., M.A. Joslyn, and J.T.R. Nickerson.Introduction to
Thermal Processing of Foods, vol. 1.Westport, CT: AVI.7. Jensen,
L.B. 1953. Man's Foods, chaps. 1, 4, 12.Champaign, IL: Garrard
Press.8. Pederson, CS. 1971. Microbiology of Food
Fermen-tations.Westport, CT: AVI.9. Schormiiller, J. 1966. Die
Erhaltung der Lebensmittel.Stuttgart: Ferdinand Enke Verlag.10.
Stewart, G.F., and M.A. Amerine. 1973. Introductionto Food Science
and Technology, chap. 1. New York:Academic Press.11. Tanner, F. W.
1944. The Microbiology of Foods, 2d ed.Champaign, IL: Garrard
Press.12. Tanner, F.W., and L.P. Tanner. 1953. Food-Borne
In-fectionsand Intoxications. 2d ed. Champaign, IL:Garrard Press.
21. PART IIHabitats, Taxonomy, andGrowth ParametersMany changes in
the taxonomy of foodborne or-ganismshave been made during the past
decade,and they are reflected in Chapter 2 along withthe primary
habitats of some organisms of con-cernin foods. The
factors/parameters that affectthe growth of microorganisms are
treated in Chap-ter3. See the following for more
information:Deak,T., and L.R. Beuchat. 1996. Handbook of Food
Spoil-ageYeasts. Boca Raton, FL: CRC Press. Detection,
enu-meration,and identification of foodborne yeasts.Doyle, M.P.,
L.R. Beuchat, TJ. Montville, eds. 1997.
FoodMicrobiologyFundamentals and Frontiers. Washing-ton,D C : ASM
Press. Food spoilage as well as foodbornepathogens are covered in
this 768-page work along withgeneral growth
parameters.International Commission on Microbiological
Specifica-tionof Foods (ICMSF). 1996. Microorganisms in Foods.5th
ed. Gaithersburg, MD: Aspen Publishers, Inc. Allof the foodborne
pathogens are covered in this 512-page work with details on growth
parameters. Well ref-erenced. 22. CHAPTER 2Taxonomy, Role, and
Significanceof Microorganisms in FoodsBecause human food sources
are of plant andanimal origin, it is important to understand
thebiological principles of the microbial biota as-sociatedwith
plants and animals in their naturalhabitats and respective roles.
Although it some-timesappears that microorganisms are trying toruin
our food sources by infecting and destroy-ingplants and animals,
including humans, thisis by no means their primary role in nature.
Inour present view of life on this planet, the pri-maryfunction of
microorganisms in nature isself-perpetuation. During this process,
the het-erotrophscarry out the following general reac-tion:All
organic matter(carbohydrates, proteins, lipids, etc.)iEnergy +
Inorganic compounds(nitrates, sulfates, etc.)This, of course, is
essentially nothing more thanthe operation of the nitrogen cycle
and the cycleof other elements (Figure 2-1). The microbialspoilage
of foods may be viewed simply as anattempt by the food biota to
carry out what ap-pearsto be their primary role in nature.
Thisshould not be taken in the teleological sense. Inspite of their
simplicity when compared to higherforms, microorganisms are capable
of carryingout many complex chemical reactions essentialto their
perpetuation. To do this, they must ob-tainnutrients from organic
matter, some of whichconstitutes our food supply.If one considers
the types of microorganismsassociated with plant and animal foods
in theirnatural states, one can then predict the generaltypes of
microorganisms to be expected on thisparticular food product at
some later stage in itshistory. Results from many laboratories show
thatuntreated foods may be expected to contain vary-ingnumbers of
bacteria, molds, or yeasts, andthe question often arises as to the
safety of a givenfood product based on total microbial numbers.The
question should be twofold: What is the to-talnumber of
microorganisms present per gramor milliliter and what types of
organisms are rep-resentedin this number? It is necessary to
knowwhich organisms are associated with a particu-larfood in its
natural state and which of the or-ganismspresent are not normal for
that particu-larfood. It is, therefore, of value to know thegeneral
distribution of bacteria in nature and thegeneral types of
organisms normally presentunder given conditions where foods are
grownand handled.BACTERIAL TAXONOMYMany changes have taken place in
the classi-ficationor taxonomy of bacteria in the past de-cade.Many
of the new taxa have been created asa result of the employment of
molecular genetic 23. Nitrogen(Atmospheric)Nitrogen
fixationAtmospheric nitrogen fixed bymany microorganisms,
e.g..Rhizobium. Ctostridium, Azotobacteretc.Figure 2-1 Nitrogen
cycle in nature is here depicted schematically to show the role of
microorganisms. Source:From Microbiology by MJ. Pelczar and R.
Reid, copyright 1965 by McGraw-Hill Book Company, used
withpermission of the publisher.methods, alone or in combination
with some ofthe more traditional methods: DNA homology and mol% G +
C contentofDNA 23S, 16S, and 5S rRNA sequence similari-ties
Oligonucleotide cataloging Numerical taxonomic analysis of
totalsoluble proteins or of a battery of morpho-logicaland
biochemical characteristics Cell wall analysis Serological profiles
Cellular fatty acid profilesAlthough some of these have been
employed formany years (e.g., cell wall analysis and
serologi-calprofiles) others (e.g., ribosomal RNA [rRNA]sequence
similarity) came into wide use only dur-ingthe 1980s. The methods
that are the mostpowerful as bacterial taxonomic tools are
out-linedand briefly discussed below.rRNA AnalysesTaxonomic
information can be obtained fromRNA in the production of nucleotide
catalogs andthe determination of RNA sequence
similarities.DenitrificationReduction of nitrates to
gaseousnitrogen by bacteria, e.g..pseudomonadsNitrate
formation(Nitrification)Nitrite oxidized to nitrate
bynitrobacterNitrate serves as plantfoodMany heterotropicspecies
reducenitrates to ammoniavia nitritesOrganic nitrogen
formation"Fixed" nitrogen utilized byplantsconverted to plant
protein;plants consumed by animals.animal proteins, etc..
formedMicroorganisms utilizeammonia as nitrogensource and
synthesizecellular proteinsNitrite formationAmmonia oxidized to
nitrite bynitrosomonasSoil organic nitrogenExcretion products of
animals,dead animals, and plant tissuedeposited in soilAmmonia
formation(Ammonification)Amino acids deaminated by
manymicroorganisms; ammonia one ofthe end products of this
processOrganic nitrogen degradationProteins, nucleic acids,
etc..attacked by a wide variety ofmicroorganisms; completebreakdown
yields mixtures ofamino acids 24. First, the prokaryotic ribosome
is a 70S (Sved-berg)unit, which is composed of two
separatefunctional subunits: 5OS and 30S. The 50S sub-unitis
composed of 23 S and 5 S RNA in addi-tionto about 34 proteins,
whereas the 30S sub-unitis composed of 16S RNA plus about
21proteins.Ribosome70S/ 3OS 50S// 16S 21 34 23S + 5SProteinsThe 16S
subunit is highly conserved and is con-sideredto be an excellent
chronometer of bacte-riaover time.48 By use of reverse
transcriptase,16S rRNA can be sequenced to produce longstretches
(about 95% of the total sequence) toallow for the determination of
precise phyloge-neticrelationships.26 Because of its smaller size,5
S RNA has been sequenced totally.To sequence 16S rRNA, a
single-strandedDNA copy is made by use of reverse transcriptasewith
the RNA as template. When the single-strandedDNA is made in the
presence ofdideoxynucleotides, DNA fragments of varioussizes result
that can be sequenced by the Sangermethod. From the DNA sequences,
the template16S rRNA sequence can be deduced. It wasthrough studies
of 16S rRNA sequences that ledWoese and his associates to propose
the estab-lishmentof three kingdoms of life-forms:
Eu-karyotes,Archaebacteria, and Prokaryotes. Thelast include the
cyanobacteria and the eubacteria,with the bacteria of importance in
foods beingeubacteria. Sequence similarities of 16S rRNAare widely
employed, and some of the newfoodborne taxa were created primarily
by its usealong with other information. Libraries ofeubacterial 5 S
rRNA sequences also exist, butthey are fewer than for
16S.Nucleotide catalogs of 16S rRNA have beenprepared for a number
of organisms, and exten-sivelibraries exist. By this method, 16S
rRNA issubjected to digestion by RNAse Tl, whichcleaves the
molecule at G(uanine) residues. Se-quences(-mers) of 6-20 bases are
produced andseparated, and similarities SAB (Dice-type
coef-ficient)between organisms can be compared. Al-thoughthe
relationship between SAB and percent-agesimilarity is not good
below SAB value of 0.40,the information derived is useful at the
phylumlevel. The sequencing of 16S rRNA by reversetranscriptase is
preferred to oligonucleotide cata-loging,as longer stretches of
rRNA can be se-quenced.Analysis of DNAThe mol% G + C of bacterial
DNA has beenemployed in bacterial taxonomy for several de-cades,and
its use in combination with 16S and5 S rRNA sequence data makes it
even moremeaningful. By 16S rRNA analysis, the
gram-positiveeubacteria fall into two groups at thephylum level:
one group with mol% G + C >55,and the other BHA >BHT.
Conidial germination of four FusariumTable 13-3 Some GRAS
Indirectly Antimicrobial Chemicals Used in FoodsCompound Primary
Use Most Susceptible OrganismsButylated hydroxyanisole (BHA)
Antioxidant Bacteria, some fungiButylated hydroxytoluene (BHT)
Antioxidant Bacteria, viruses, fungif-Butylhydroxyquinoline (TBHQ)
Antioxidant Bacteria, fungiPropyl gallate (PG) Antioxidant
BacteriaNordihydroguaiaretic acid Antioxidant
BacteriaEthylenediaminetetraacetic acid (EDTA)
Sequestrant/stabilizer BacteriaSodium citrate Buffer/sequestrant
BacteriaLaurie acid Defoaming agent Gram-positive
bacteriaMonolaurin Emulsifier Gram-positive bacteria,
yeastsDiacetyl Flavoring Gram-negative bacteria, fungid- and
/-Carvone Flavoring Fungi, gram-positive bacteriaPhenylacetaldehyde
Flavoring Fungi, gram-positive bacteriaMenthol Flavoring Bacteria,
fungiVanillin, ethyl vanillin Flavoring FungiSpices/spice oils
Flavoring Bacteria, fungi 268. spp. was inhibited by 200 ppm BHA or
propylparaben (PP) over the pH range 4-10, but over-all,PP was more
inhibitory than BHA.114Foodborne pathogens such as Bacillus
cereus,Vparahaemolyticus, salmonellae, and S. aureusare effectively
inhibited at concentrations 6.0 is not effec-tive.Shelf life of
vacuum-packaged fish isshortened by the growth
of'Photobacteriumphosphoreum16 and Shewanella putre-faciens.l In
general, the gram-negative bacteria aremore sensitive to CO2
inhibition than grampositives, with pseudomonads being amongthe
most sensitive and clostridia the mostresistant (Table 14-4). Upon
prolonged stor-ageof meats, CO2 effects a rather dramaticshift in
biota from one that is largely gramnegative in fresh products to
one that islargely or exclusively gram positive. Thiscan be seen in
Table 14-5 for smoked porkloins and frankfurter sausage.6 Both lag
and logrithmic phases of growthare retarded. CO2 under pressure is
considerably moreantimicrobial than not, and pressures of6 to 30
megapascal (mPa) can destroy bac-teriaand fungi under varying
conditions (seeHigh Hydrostatic Pressure in Chapter 19).The
destructive action is believed to occurwhen pressure is released
suddenly.Mode of ActionAs to the mechanism of CO2 inhibition of
mi-croorganisms,two explanations have been of-fered.King and
Nagel60 found that CO2 blockedTable 14-4 Relative Sensitivity
ofMicroorganisms to CO2 Relative to Vacuum-andModified-Atmosphere
PackagingPseudomonas spp. (most sensitive)Aeromonas spp.Bacillus
spp.MoldsEnterobacteriaceaeEnterococcus spp.Brochothrix
spp.Lactobacillus spp.Clostridium spp. (most resistant)Source:
Adapted with permission from G. Molin69, The Re-sistanceto Carbon
Dioxide of Some Food Related Bacteria,European Journal of Applied
Microbiology and Biotechnology,Vol. 18, pp. 214-217, 1983,
Springer-Verlag New York, Inc. 288. Table 14-5 Effect of Storage on
the Microbiota of Two Meats Held from 48 to 140 Days at 4Cthe
metabolism of Pseudomonas aeruginosa andappeared to effect a mass
action on enzymaticdecarboxylations. Sears and Eisenberg78
foundthat CO2 affected the permeability of cell mem-branes,and
Enfors and Molin23 found supportfor the latter hypothesis in their
studies on thegermination of Clostridium sporogenes and
C.perfringens endospores. At 1 atm CO2, sporegermination of these
two species was stimulated,whereas B. cereus spore germination was
inhib-ited.As was shown by others, CO2 is more stimu-latoryat low
pH than high. With 55 atm CO2,only 4% germination of C. sporogenes
sporesoccurred, whereas with C. perfringens, 50 atmreduced
termination to 4%.23 These authors sug-gestedthat CO2 inhibition
was due to its accu-mulationin the membrane lipid bilayer such
thatSmoked Pork Loinsincreased fluidity results. An adverse effect
oncell permeability has been suggested by others.IfCO2 is dissolved
in the form of carbonic acid,HCO3" would be present as a
dissociation prod-uct,and thus can cause changes in cell
perme-ability.17 When dissolved in water, CO2 productsare as
follows:CO2 + H2O ; H2CO3^ H+ + HCO3" ; 2H+ + CO32-The
antimicrobial spectrum of CO2 anddiacetyl is quite similar, and
while this per sedoes not mean they possess identical modes
ofaction, the striking similarities seem worthy ofnote. Diacetyl is
an arginine antagonist and itsmode of action along with some other
a-dicar-bonylcompounds has been discussed.54 TheLog APC/gPHDominant
biota (%)O Day2.55.8Flavo (20)Arthro (20)Yeasts (20)Pseudo
(11)Coryne (10)Vacuum48 Days7.65.8Lactos (52)aCO248
Days6.95.9Lactos (74)bN248 Days7.25.9Lactos (67)cFrankfurter
SausageLog APC/gPHDominant biota (%)O Day1.75.9Bac (34)Coryne
(34)Flavo (8)Broch (8)Vacuum98 Days9.05.4Lactos (38)CO2140
Days2.45.6Lactos (88)dN2140 Days4.85.9Lactos (88)eNote: Percentage
biota represented by Weissella viridescens: a40; b72; c50; d22;
e35. APC = aero-bicplate count; Flavo = Flavobacterium; Arthro =
Arthrobacter; Pseudo = Pseudomonas; Coryne =Corynebacterium; Bac =
Bacillus; Broch = Brochothrix.Source: Adapted from Blickstad and
Molin.6 289. greater sensitivity of gram-negative bacteria
toa-dicarbonyl inhibitors appears to be due to theircapacity to
inactivate amino acid-binding pro-teinsof the cell's periplasm,
especially the argi-nine-binding proteins. Thus, it is not
inconceiv-ablethat the site of action of CO2 is the periplasm,where
it interferes with the normal functioningof amino acid-binding
proteins. Further discus-sionsof possible modes of action of CO2
can befound in references 18 and 21.FOOD PRODUCTSThe successful use
of vacuum packaging,MAP, and CAS to extend the shelf life of a
widevariety of food products is well documented, andsome of the
specific antimicrobial aspects areoutlined below.Fresh and
Processed MeatsAmong the first to demonstrate the effective-nessof
high levels of CO2 in preserving cut-upmeats was J. Brooks in
England, who in 1933studied the effect of CO2 on lean meat; E.
Cal-lowin England, who studied pork and bacon;R.B. Haines, also in
England, who was amongthe first to show the effect of CO2 on
spoilageorganisms; and W.A. Empey in Australia, whoin 1933 applied
CO2 to beef73In general, the shelf life of red meats can beextended
for up to 2 months if packaged in 75%O2 + 25% CO2 and stored at
-10C. The high levelof oxygen ensures that the red-meat color
ismaintained. It has been shown that at least 15%CO2 is necessary
to retard microbial growth onbeef steaks, and that the mixture of
15% CO2 +75% O2 + 10% N2 was more effective thanvacuum both for
red-meat color and microbialquality.4 The importance of temperature
of stor-ageof MAP meats was shown early by Jaye etal.,55 who found
striking differences in qualitywhen ground beef was stored at 30
versus 38.They compared the use of the more gas-imper-meableSaran
to the gas-permeable cellophanepacks. Earlier, Halleck et al.40
showed the dra-maticinhibitory effect of vacuum packaging
andstorage at 1.1-3.3 0C. The importance of tempera-tureof storage
was demonstrated in another studyusing the packaging system known
as theCaptech process, which combines hygienic pro-cessing,storage
at -1.50C, high CO2, low O2, andgas-impermeable packaging.39 The
process wasapplied to pork loins, with the temperature ofholding
for simulated retail display being raisedto 8C. Lactic acid
bacteria grew withoutperceptible decrease in lag phase, and
reached107/cm2 within 9 weeks. The behavior of the biotaof smoked
pork loins and frankfurter sausagestored under vacuum and CO2 is
presented inTable 14-5. As is typical of MAP meats, the
ini-tialheterogeneous biota became homogeneousupon long-term
storage under vacuum or MAPwith pH being decreased due to
predominanceof lactic acid bacteria.6The relative effectiveness of
MAP/vacuumpackaging of red meats can be assessed by
de-terminingchanges that occur in hydration capac-ity.When fresh
ground beef was stored in high-barrierbags and held at 7C for up to
13 days,the hydration capacity was essentially unchangedin
comparison to the samples that were looselywrapped in foil to allow
for aerobic conditions(Figure 14-1). This is reflected by
extract-releasevolume (ERV) (see Chapter 4). Over the
hold-ingperiod, gram-negative bacteria increased byabout 6 log10
but by only 3 log10 for the aerobi-callystored foil-wrapped and
high-barrier bag-storedmeats, respectively. Similar results can
beobtained by using the filter-paper press methodto measure
hydration capacity.53 The increasedhydration is brought about by
the preferentialgrowth of lactic acid bacteria, which depress pH.In
their study of beef and pork livers and beefkidneys packaged in
high-barrier bags, Hannaet al.45 found that pH decreased in each
productwhen held at 2C for up to 28 days. ERV hasbeen used to
assess the spoilage of vacuum-pack-agedmeats.75Overall, the storage
of fresh meats undervacuum or MAP has been very successful andsafe.
The latter is in large part a reflection of theexistence of lactic
acid and related bacteria on 290. DAYSFigure 14-1 Lack of increase
in hydration capacity of fresh ground beef stored in high-barrier
bags at 7C for13 days as measured by extract-release volume (ERV).
The foil-wrapped samples underwent aerobic spoilageas evidenced by
increased hydration and endotoxin titers.fresh meats, and when
these products are storedunder low O2 and high CO2 conditions at
lowtemperatures, the normal biota prevents thegrowth of pathogens
by virtue of depressed pH,competition for O2, possible production
of anti-microbialsubstances, and other factors.PoultryThe
effectiveness of MAP for the storage offresh poultry was
demonstrated in the early1950s73 and since that time a number of
studieshave been reported. Hotchkiss51 used from 60%to 80% CO2 on
raw poultry in glass jars and foundan increase in shelf life to at
least 35 days at2C. In another study, when high-barrier film(oxygen
transmission rate [OTR] ca. 18 mL) wasused to pack cut-up or whole
chicken that washeld at 5C, the chicken had lower numbers
ofbacteria and kept longer than that which wasstretch-wrapped with
a film that had an OTR of6,500 mL, and this is illustrated in
Figure 14-2.61With poultry stored in air, the aerobic plate
count(APC) of drip after 16 days at 100C was 9.40 log10,whereas in
20% CO2 the APC was 6.14 log10.92Overall, the generally higher
initial pH of freshpoultry meat is primarily responsible for
thisproduct's not having the MAP shelf life of prod-uctssuch as
fresh beef.SeafoodsMAP/vacuum packaging has been shown toextend the
shelf life of cod fillets, red snapper,rainbow trout, herrings,
mackerel, sardines, cat-fish,and others. In 1933, EP. Coyne of
Englandwas apparently the first person to show the
pre-servativeeffects of CO2 on fish.73For fish using 80% CO2 + air,
log numbersafter 14 days at 35C were approximatelyERVLOG. NOS.
& TITER 291. DAYS IN STORAGE AT 5CFigure 14-2 Numbers of total
aerobic mesophilicbacteria from packaged whole chickens under
aero-bic(tray pack) and vacuum-pack storage. Source: Re-printedwith
permission from J. Kraft et al., Micro-biologicalQuality of Vacuum
Packaged Poultry withor without Chlorine Treatment, Journal of Food
Sci-ence,Vol. 47, p. 381, 1982, Institute of Food
Tech-nologists.6.00/cm2 compared to air controls with log
num-bers>10.5 cm2. The pH of CO2-stored productsafter 14 days
decreased from around 6.75 toaround 6.30, whereas controls
increased toaround 7.45.74 The shelf life of rockfish andsalmon at
4.5C was extended by 20-80% CO2.8At least 1 log difference in
bacterial counts overcontrols was obtained when trout and
croakerwere stored in CO2 environments at 4C.42 Whenfresh shrimp or
prawns were packed in ice withan atmosphere of 100% CO2, they were
ediblefor up to 2 weeks, and bacterial counts after 14days were
lower than air-packed controls after 7days.65 When cod fillets were
stored at 2C, air-storedsamples spoiled in 6 days, with APC oflog10
7.7, whereas samples stored in 50% CO2 +50% O2 or 50% CO2 + 50% N2
or 100% CO2 didnot show bacterial spoilage until,
respectively,26,34, and 34 days, with respective APCs of 7.2,6.6,
and 5.5/g.88 It was suggested that the use of50% CO2 + 50% O2 is
technically more feasiblethan the use of 100% CO2. Whereas the
practi-calupper limit of CO2 for red meats is around20%, higher
concentrations can be used with fishbecause they contain lower
levels of myoglobin.The concern over the use of MAP for
fisheryproducts has to do with the fact that
nonproteo-lyticbotulism strains are found in waters and theycan
grow at temperatures