8 MODERN FOOD MICROBIOLOGY 1965-Foodborne giardiasis was recognized. 1969-C.perfringens enterotoxin was demonstrated by C.L.Duncan and D.H.Strong -C.botulinum type G was first isolated in Argentina by Gimenez and Ciccarelli. 1971-First U.S.foodbome outbreak of Vibrioparahaemolyticus gastroenteritisoccurredin Maryland. -First documented oubreak of E.coli foodbore gastroenteritis occurred in the United States. strated by L. oupal and R. b -In ed in Calif red in New York 1977The first documented outbreak of cyclosporiasis occurred in Papua.New Guinea:first in United States in 1990. 1978-Documented foodborne outbreak of gastroenteritis caused by the Norwalk virus occurred in Australia. 1979Foodborne gastroenteritis aused by non-01 Vibrio cholerae occurred in Florida.Earlier out vakia (1965)and A 1083 toxin was described by Ruiz-Palacios et al. 1985The irradiation of pork to0.3 to 1.0 kGy to control Trichinella spiralis was approved in the United States. 1986-Bovine spongiform encephalopathy(BSE)was first diagnosed in cattle in the United Kingdom. Food Legislation 1890-The first tioal meat inspection aws inspection of ats for 1895 export only 1906 The US Fede Food and Dn en its provisions 1910The New York City Board of Health issued an order requiring the pasteurization of milk 1939-The new Food,Drug,and Cosmetic Act became law. 1954-The Miller Pesticide Chemicals Amendment to the Food,Drug,and Cosmetic Act was passed by Congress. 1957 oulsory Poultry and Pou Itry Pi ducts law was enacted lmadge-A its An nent to the osmetics Act was passed 1963-The U.S.Food and Drug Administration approved the use of irradiation for the preservation of bacon. 1967-The U.S.Wholesome Meat Act was passed by Congress and enacted into law on December 1968 -The Food and Drug Administration withdrew its 1963 approval of irradiated bacon. 1969he n Bil Administration established an allowable level of 20 ppb of aflatoxin 1973The state of Oregon adopted microbial standards for fresh and processed retail meat.They were repealed in 1977
8 Modern Food Microbiology 1965—Foodborne giardiasis was recognized. 1969—C. perfringens enterotoxin was demonstrated by C.L. Duncan and D.H. Strong. —C. botulinum type G was first isolated in Argentina by Gimenez and Ciccarelli. 1971—First U.S. foodborne outbreak ofVibrio parahaemolyticus gastroenteritis occurred inMaryland. —First documented outbreak of E. coli foodborne gastroenteritis occurred in the United States. 1975—Salmonella enterotoxin was demonstrated by L.R. Koupal and R.H. Deibel. 1976—First U.S. foodborne outbreak of Yersinia enterocolitica gastroenteritis occurred in New York. —Infant botulism was first recognized in California. 1977—The first documented outbreak of cyclosporiasis occurred in Papua, New Guinea; first in United States in 1990. 1978—Documented foodborne outbreak of gastroenteritis caused by the Norwalk virus occurred in Australia. 1979—Foodborne gastroenteritis caused by non-01 Vibrio cholerae occurred in Florida. Earlier outbreaks occurred in Czechoslovakia (1965) and Australia (1973). 1981—Foodborne listeriosis outbreak was recognized in the United States. 1982—The first outbreaks of foodborne hemorrhagic colitis occurred in the United States. 1983—Campylobacter jejuni enterotoxin was described by Ruiz-Palacios et al. 1985—The irradiation of pork to 0.3 to 1.0 kGy to control Trichinella spiralis was approved in the United States. 1986—Bovine spongiform encephalopathy (BSE) was first diagnosed in cattle in the United Kingdom. Food Legislation 1890—The first national meat inspection law was enacted. It required the inspection of meats for export only. 1895—The previous meat inspection act was amended to strengthen its provisions. 1906—The U.S. Federal Food and Drug Act was passed by Congress. 1910—The New York City Board of Health issued an order requiring the pasteurization of milk. 1939—The new Food, Drug, and Cosmetic Act became law. 1954—The Miller Pesticide Chemicals Amendment to the Food, Drug, and Cosmetic Act was passed by Congress. 1957—The U.S. Compulsory Poultry and Poultry Products law was enacted. 1958—The Food Additives Amendment to the Food Drug, and Cosmetics Act was passed. 1962—The Talmadge-Aiken Act (allowing for federal meat inspection by states) was enacted into law. 1963—The U.S. Food and Drug Administration approved the use of irradiation for the preservation of bacon. 1967—The U.S. Wholesome Meat Act was passed by Congress and enacted into law on December 15. 1968—The Food and Drug Administration withdrew its 1963 approval of irradiated bacon. —The Poultry Inspection Bill was signed into law. 1969—The U.S. Food and Drug Administration established an allowable level of 20 ppb of aflatoxin for edible grains and nuts. 1973—The state of Oregon adopted microbial standards for fresh and processed retail meat. They were repealed in 1977
History of Microorganisms in Food 9 REFERENCES 1.Bishop.P.W.1978.Who introduced the tin can?Nicolas Appert?Peter Durand?Bryan Donkin?Food Technol.32:60-67. 2.Brandly,PG.Migaki,and KE.Taylor.1966.Mear Hygene,3rded.chap.1.Philadelphia:Lea&Febiger 3.Cowell,N.D.1995.Who introduced the tin can?-Anew candidate.Food Techno.9:61-64. 4.Farrer,K.T.H.1979.Who invented the brine bath?-The Isaac Solomon myth.Food Technol.33:75-77 .Goldblith,S.A.1971.A cond ensed history of the science and technology of themal processing Food:44-50. 6.Jensen.L.B.1953.Man's Foo s,chaps.1.4.12.Cha 1999.The life and work of Nicolas Appert.1749-1841.Abstract#7-1.p.10. 8.Pederson.CS.1971.Microbiology of Food Fermentations.Westport.CT:AVL 9.Schormiller,J.1966.Die Erhalng der Lebensmiel Stuttgar:Ferdinand Enke Verlag. 10.Stewart.G. and M.A.Amerine.1973.Introd Science and Techmology.chap.1.New York:Academic Press a2adedCanpaignLGamrdPnes
History of Microorganisms in Food 9 REFERENCES 1. Bishop, P.W. 1978. Who introduced the tin can? Nicolas Appert? Peter Durand? Bryan Donkin? Food Technol. 32:60–67. 2. Brandly, P.J., G. Migaki, and K.E. Taylor. 1966. Meat Hygiene, 3rd ed., chap. 1. Philadelphia: Lea & Febiger. 3. Cowell, N.D. 1995. Who introduced the tin can?—A new candidate. Food Technol. 49:61–64. 4. Farrer, K.T.H. 1979. Who invented the brine bath?—The Isaac Solomon myth. Food Technol. 33:75–77. 5. Goldblith, S.A. 1971. A condensed history of the science and technology of thermal processing. Food Technol. 25:44–50. 6. Jensen, L.B. 1953. Man’s Foods, chaps. 1, 4, 12. Champaign, IL: Garrard Press. 7. Livingston, G.E., and J.P. Barbier. 1999. The life and work of Nicolas Appert, 1749–1841. Abstract # 7-1, p. 10, Institute of Food Technol. Proceedings. 8. Pederson, C.S. 1971. Microbiology of Food Fermentations. Westport, CT: AVI. 9. Schorm ¨uller, J. 1966. Die Erhaltung der Lebensmittel. Stuttgart: Ferdinand Enke Verlag. 10. Stewart, G.F., and M.A. Amerine. 1973. Introduction to Food Science and Technology, chap. 1. New York: Academic Press. 11. Tanner, F.W. 1944. The Microbiology of Foods, 2nd ed. Champaign, IL: Garrard Press. 12. Tanner, F.W., and L.P. Tanner. 1953. Food-Borne Infections and Intoxications, 2nd ed. Champaign, IL: Garrard Press
CHAPTER 2 Taxonomy,Role,and Significance of Microorganisms in Foods Because human food sources are of plant and animal ori in, it is important to understand the anisms are ns to rin our food sources by infecting and destroying plants and animals,including humans.this is by no means their primary role in nature.Inourpresent view of life on this planet,the primary function of microorganisms in nature is self-perpetuation.During this process,the heterotrophs and autotrophs carry out the following general reaction: All organic matter (carbohydrates,proteins,lipids,etc.) This,of course nothi of the mrogen cyc e of other ele nt by tocarry out what a ears to be their primaryole innature.This should not be taken n the tec sense.In spite of their simplicity when compared to higher forms,microorganisms are capable of carrying out many complex chemical reactions essential to their perpetuation.To do this.they must obtain nutrients from organic matter,some of which constitutes our food supply. I one considers the types of microorganisms a sociated with plant and animal foods in their natura 606e s particu y and the as to the safety food product based on total microbial numbers.The question should be twofold:What is the total number of microorganisms present per gram or milliliter and what rypes of organisms are represented in this number?It is necessary to know which organisms are associated with a particular food in its natural state and which of the organisms present are not normal for that particular 13
Chapter 2 Taxonomy, Role, and Significance of Microorganisms in Foods Because human food sources are of plant and animal origin, it is important to understand the biological principles of the microbial biota associated with plants and animals in their natural habitats and respective roles. Although it sometimes appears that microorganisms are trying to ruin our food sources by infecting and destroying plants and animals, including humans, this is by no means their primary role in nature. In our present view of life on this planet, the primary function of microorganisms in nature is self-perpetuation. During this process, the heterotrophs and autotrophs carry out the following general reaction: All organic matter (carbohydrates, proteins, lipids, etc.) ↓ Energy + Inorganic compounds (nitrates, sulfates, etc.) This, of course, is essentially nothing more than the operation of the nitrogen cycle and the cycle of other elements. The microbial spoilage of foods may be viewed simply as an attempt by the food biota to carry out what appears to be their primary role in nature. This should not be taken in the teleological sense. In spite of their simplicity when compared to higher forms, microorganisms are capable of carrying out many complex chemical reactions essential to their perpetuation. To do this, they must obtain nutrients from organic matter, some of which constitutes our food supply. If one considers the types of microorganisms associated with plant and animal foods in their natural states, one can then predict the general types of microorganisms to be expected on this particular food product at some later stage in its history. Results from many laboratories show that untreated foods may be expected to contain varying numbers of bacteria, molds, or yeasts, and the question often arises as to the safety of a given food product based on total microbial numbers. The question should be twofold: What is the total number of microorganisms present per gram or milliliter and what types of organisms are represented in this number? It is necessary to know which organisms are associated with a particular food in its natural state and which of the organisms present are not normal for that particular food. It is, therefore, of value to know the general distribution of bacteria in nature and the general types of organisms normally present under given conditions where foods are grown and handled. 13
14 MODERN FOOD MICROBIOLOGY BACTERIAL TAXONOMY Many changes have taken place in the classification or taxonomy of bacteria in the past two decades Many of the new taxa have been created as a result of the employment of molecular genetic methods. alone or in combination with some of the more traditional methods: 1.DNA homology and mol%G+C content of DNA 2.23S,16S,and 5S rRNA sequence similarities 3.Oligonucleotide cataloging 4.Numerical taxonomic analysis of total soluble proteins or of a battery of morphological and the 1980s.The methods that are the most powerful as bacteril taxonomic tools are outined and briefy discussed below. rRNA Analyses Taxonomic information can be obtained from RNA in the production of nucleotide catalogs and the which isRM Ned of plus about hereas the 05 it is compose pro Ribosome 70s 30s 16S2134 23S+5S Proteins The 16S subunit is highly conserved and is considered to be an excellent chronometer of bacteria ing reverse transcnptas 1os rk A can be sequence I to produce long stre chain reaction (PCR)-ased methods. To sequence 16S rRNA.a single-stranded DNA copy is made by use of reverse transcriptase with the RNA as template.When the single-stranded DNA is made in the presence of dideoxynucleotides
14 Modern Food Microbiology BACTERIAL TAXONOMY Many changes have taken place in the classification or taxonomy of bacteria in the past two decades. Many of the new taxa have been created as a result of the employment of molecular genetic methods, alone or in combination with some of the more traditional methods: 1. DNA homology and mol% G + C content of DNA 2. 23S, 16S, and 5S rRNA sequence similarities 3. Oligonucleotide cataloging 4. Numerical taxonomic analysis of total soluble proteins or of a battery of morphological and biochemical characteristics 5. Cell wall analysis 6. Serological profiles 7. Cellular fatty acid profiles Although some of these have been employed for many years (e.g., cell wall analysis and serological profiles) others (e.g., ribosomal RNA [rRNA] sequence similarity) came into wide use only during the 1980s. The methods that are the most powerful as bacterial taxonomic tools are outlined and briefly discussed below. rRNA Analyses Taxonomic information can be obtained from RNA in the production of nucleotide catalogs and the determination of RNA sequence similarities. First, the prokaryotic ribosome is a 70S (Svedberg) unit, which is composed of two separate functional subunits: 50S and 30S. The 50S subunit is composed of 23S and 5S RNA in addition to about 34 proteins, whereas the 30S subunit is composed of 16S RNA plus about 21 proteins. The 16S subunit is highly conserved and is considered to be an excellent chronometer of bacteria over time.53 Using reverse transcriptase, 16S rRNA can be sequenced to produce long stretches (about 95% of the total sequence) to allow for the determination of precise phylogenetic relationships.31 Alternatively, the 16S rDNA may be sequenced after amplification of specific regions by polymerase chain reaction (PCR)-based methods. To sequence 16S rRNA, a single-stranded DNA copy is made by use of reverse transcriptase with the RNA as template. When the single-stranded DNA is made in the presence of dideoxynucleotides
Taxonomy,Role,and Significance of Microorganisms in Foods 15 DNA fragments of various sizes result that can be sequ nced by the sanger method.From the dNA sequences,the template 16S rRNA sequence can be deduced.It was through studies of 16S rRNA sequences that led Woese and his associates to propose the establishment of three kingdoms of life forms:Eukaryotes,Archaebacteria,and Prokaryotes.The last include the cyanobacteria and the e bacteria,with the bacteria of importance in foods being eubacteria.Sequence similarities of 16SrRNA re wid new food Nucleotide catalogs of 16s rRNA have heen prenared for a numher of organisms and extensive libraries exist.By this method,16S rRNA is subjected to digestion by RNase T1,which cleaves the molecule at G(uanine)residues.Sequences (-mers)of 6-20 bases are produced and separated.and similarities SAB(Dice-type coefficient)between organisms can be compared.Although the relationship between SAB and percentage similarity is not good below SAB value of 0.40.the information derived e phyl m by reverse transcriptase is preferred to can be sequenced Analysis of DNA The mol%G+C of bacterial DNA has been employed in bacterial taxonomy for several decades 16S rRNAmon with 16S and 5S rRNA sequence data makes it even more mea analy e Gr -po a fall into t groups at the phylum level:one group with the lower G+C yalues include the Clos Ra Pediococcus,Leuconostoc,Listeria,Erysipelothrix,and others.The latter group is referred to as the Clostridium branch of the eubacterial tree.When two organisms differ in G+C content by more than e,and this technique continues to be o o great value in ctenal systema It has been noted tha the 9 ed th complete DNA sequence of an NA h s generall 70g and 5o int)d s 50 Whe noceseae2Da,2oqeae Even if there is not yet a satisfactory phylogenetic definition of a bacterial genus.the continue pplica niques,along with some of the other methods listed above,should lea d system of bacterial systematics.In the meantime,changes in The proteobacteria The Gram-negative bacteria of known importance in foods belong to the class Proteobacteria. which was established following extensive studies on the rRNA sequences of numerous genera of
Taxonomy, Role, and Significance of Microorganisms in Foods 15 DNA fragments of various sizes result that can be sequenced by the Sanger method. From the DNA sequences, the template 16S rRNA sequence can be deduced. It was through studies of 16S rRNA sequences that led Woese and his associates to propose the establishment of three kingdoms of life forms: Eukaryotes, Archaebacteria, and Prokaryotes. The last include the cyanobacteria and the eubacteria, with the bacteria of importance in foods being eubacteria. Sequence similarities of 16S rRNA are widely employed, and some of the new foodborne taxa were created primarily by its use along with other information. It appears that the sequencing of 23S rDNA will become more widely used in bacterial taxonomy. Nucleotide catalogs of 16S rRNA have been prepared for a number of organisms, and extensive libraries exist. By this method, 16S rRNA is subjected to digestion by RNase T1, which cleaves the molecule at G(uanine) residues. Sequences (-mers) of 6–20 bases are produced and separated, and similarities SAB (Dice-type coefficient) between organisms can be compared. Although the relationship between SAB and percentage similarity is not good below SAB value of 0.40, the information derived is useful at the phylum level. The sequencing of 16S rRNA by reverse transcriptase is preferred to oligonucleotide cataloging, as longer stretches of rRNA can be sequenced. Analysis of DNA The mol% G + C of bacterial DNA has been employed in bacterial taxonomy for several decades, and its use in combination with 16S and 5S rRNA sequence data makes it even more meaningful. By 16S rRNA analysis, the Gram-positive eubacteria fall into two groups at the phylum level: one group with mol% G + C >55, and the other <50.53 The former includes the genera Streptomyces, Propionibacterium, Micrococcus, Bifidobacterium, Corynebacterium, Brevibacterium, and others. The group with the lower G + C values include the genera Clostridium, Bacillus, Staphylococcus, Lactobacillus, Pediococcus, Leuconostoc, Listeria, Erysipelothrix, and others. The latter group is referred to as the Clostridium branch of the eubacterial tree. When two organisms differ in G + C content by more than 10%, they have few base sequences in common. DNA–DNA or DNA–RNA hybridization has been employed for some time, and this technique continues to be of great value in bacterial systematics. It has been noted that the ideal reference system for bacterial taxonomy would be the complete DNA sequence of an organism.49 It is generally accepted that bacterial species can be defined in phylogenetic terms by use of DNA–DNA hybridization results, where 70% or greater relatedness and 5◦C or less Tm (melting point) defines a species.50 When DNA–DNA hybridization is employed, phenotypic characteristics are not allowed to override except in exceptional cases.50 Although a genus is more difficult to define phylogenetically, 20% sequence similarity is considered to be the minimum level of DNA–DNA homology.50 Even if there is not yet a satisfactory phylogenetic definition of a bacterial genus, the continued application of nucleic acid techniques, along with some of the other methods listed above, should lead ultimately to a phylogenetically based system of bacterial systematics. In the meantime, changes in the extant taxa may be expected to continue to occur. The Proteobacteria The Gram-negative bacteria of known importance in foods belong to the class Proteobacteria, which was established following extensive studies on the rRNA sequences of numerous genera of