An Evaluation of the Role of Microbiological Criteria for Foods and Food Ingredients (1985) / Chapter Skim
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5 Selection of Indicator Organisms and Agents as Components of Microbiological Criteria
5 Selection of Indicator Organisms and Agents as Components of Microbiological Criteria
Pages 104-131
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From page 104... ...
the aerobic plate count, thermoduric, psychrotrophic, thermophilic, proteolytic, and lipolytic counts; the direct microscopic count; Howard mold count; rot fragment count; "machinery mold"; yeast and mold count; heat-resistant molds and thermophilic spore count; and (2) examination for metabolic products such as by organoleptic examination, dye or indicator reduction time, pH, trimethylamine (TMA)
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From page 105... ...
ASSESSMENT OF NUMBERS OF MICROORGANISMS AND/OR MICROBIAL ACTIVITY Estimating Numbers of Microorganisms Aerobic Plate Count The aerobic plate count (APC) is used as part of a microbiological standard for raw and pasteurized milk and many other dairy products, and for shellfish at the wholesale level (see Chapters 8 and 91.
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From page 106... ...
Specific causes of unexpected high counts can be identified by examination of samples at critical control points and by plant inspection. However, even perishable foods prepared from wholesome raw materials and properly processed, packaged, and stored develop high counts, lose quality, and ultimately spoil if held for long periods.
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From page 107... ...
is used in the milk industry to check individual producer milk in order to identify samples with excessive numbers of these organisms. Thermoduric organisms survive pasteurization of milk and thus may contribute to high SPCs on pasteurized milk.
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From page 108... ...
and the standard plate count (SPC) method as described in Standard Methods for the Examination of Dairy Products (APHA, 19781.
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From page 109... ...
Practical methods for these mold counts are applicable for microbiological criteria (AOAC, 1980; APHA, 1976, 19841. There is a sufficiently close relationship between the Howard mold and rot fragment counts and the amount of decayed tissue present for the counts to serve as useful microbiological criteria for certain fruits and vegetable products and to be an index of manufacturing practices.
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From page 110... ...
Yeast and Mold Counts Yeast and mold counts are used as part of microbiological standards of various dairy products, for example cottage cheese (Chapter 8, Table 84) and sugar (National Soft Drink Association, 19751.
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From page 111... ...
Use of organoleptic examinations of foods to evaluate microbial activity is limited, as the effect of microbes on organoleptic attributes varies. Certain microorganisms act upon the constituents of a food and produce marked changes in perceptible characteristics of the food; others are relatively inert biochemically and produce little change.
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From page 112... ...
For example, organoleptic examinations are used to evaluate the amount of acid and/or aroma compounds produced by various lactic acid bacteria in cultured dairy products. The organoleptic evaluation of cheese for typical flavor and body and texture, to a large extent, reflects the activities of desirable bacteria.
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From page 113... ...
With improvements in milk quality resulting in lower bacterial counts, reduction tests have become less applicable for quality evaluation of raw milk. Results of oxidation-reduction tests on pasteurized milk can be used by the processor as guidelines for estimation of the potential shelf-life of freshly pasteurized milk.
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From page 114... ...
114 au 0 v: cat · _ · _ u, cd Cal cat ct .e s ct . ~ a' o to O cat ._ 04 ct v, of ~ .~ oo Vl Vl Cal ret 0 -1 0 0 ~ ~ ~ ~ 0 ~ 0 cacat ._._ ~ ° Ea ~ E a ~ ~ 00 , ~ ~04 ~ ~ - ° ~ vg o 1 to Vl m 00 of 1 to O ~ .
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From page 115... ...
115 aid =A 0 0 \~)
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From page 116... ...
The goal of these voluntary guidelines is to provide an understanding of the critical control points in the fermentation stage of production of dry and semidry fermented sausages in order to minimize the opportunity for Staphylococcus aureus to develop. In the-production of cultured milk products and cheeses, measurement of pH of the inoculated milk is also of great importance as it monitors the rate of development of lactic acid bacteria.
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From page 117... ...
Lactic acid bacteria were predominant on the fish stored under modified gaseous atmospheres, whereas gram-negative, aerobic rods usually predominated on samples exposed to air. Reliable methods are available to determine TMA and TVN (AOAC, 1980; Cobb et al., 19731.
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From page 118... ...
The present analytical method for the ethanol determination, although relatively simple and rapid, requires sophisticated laboratory equipment. D,ace~l The diacetyl test was developed in the citrus industry to indicate microbial activity in the early stages of multiple-stage, low-temperature evap
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From page 119... ...
In this procedure, histaminase acts on histamine, forming hydrogen peroxide which is then broken down by peroxidase with simultaneous formation of crystal violet from the oxidation of its leuco form. If further studies confirm that this test has satisfactory sensitivity, then it could be a valuable tool to monitor incoming scombroid fish for toxic levels of histamine (resulting from extensive microbial growth)
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From page 120... ...
At the present no practical routine methods exist to apply ATP as a parameter to evaluate the microbiological condition of foods. ASSESSMENT OF INDICATORS Indicators of Potential Human or Fecal Contamination or Possible Presence of Pathogens Staphylococci Staphylococci originate from the nasal passages, skin, and lesions of man and other mammals.
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From page 121... ...
At present, E cold is the best indicator of fecal contamination among the commonly used fecal-indicator organisms.
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From page 122... ...
Fecal Coliforms Fecal coliform bacteria! are used as a component of microbiological standards to monitor the Wholesomeness of shellfish and the quality of shellfish growing waters (USDHEW, 19651.
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From page 123... ...
cold rather than fecal coliforms as a component of microbiological criteria for foods. Enterococci Enterococci have certain features that make them unique as indicator organisms.
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From page 124... ...
Indicators of Post-Heat Processing Contamination Coliform Bacteria Coliform bacteria are members of the Enterobacteriaceae that are capable of fermenting lactose with the production of acid and gas within 48 hours at 35°C (95°F) ; for dairy products some workers specify 32°C (89.6°F)
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From page 125... ...
From their original fecal, soil, water, or plant environment, coliform bacteria can reach the food processing plant, food service establishment, or home environment, where they may be spread via equipment and utensil surfaces or by employees. The presence of coliforms in food does not necessarily mean that there was fecal contamination or that pathogens are present.
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From page 126... ...
Whether or not the Enterobacteriaceae count should supplant the coliform count in microbiological criteria is a debatable question. TESTS FOR OTHER COMPONENTS Tests for Metabolic Products of Pathogens That Indicate a Health Hazard In a number of circumstances, tests for metabolic products of pathogens are preferred to tests for pathogens (see Chapter 4)
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From page 127... ...
Test for Phosphatase The phosphatase test is part of a criterion for certain milk and milk products to determine whether the product in question was pasteurized properly and also to detect the possible addition of raw milk to pasteurized milk (APHA, 1978; USPHS/FDA 19781. Methods, limitations, and interpretation of test results are presented in detail in Standard Methods for the Examination of Dairy Products (APHA, 19781.
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From page 128... ...
1981 Defect action level for decomposition in imported canned and cooked frozen shrimp; availability of guide. Federal Register 46:39221.
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From page 129... ...
W 1976 Potential health hazards associated with Pseudomonas aeruginosa in water.
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From page 130... ...
XIII. An international comparative study of the MEN procedure and the Anderson-Baird-Parker direct plating method for the enumeration of Escherichia cold biotype 1 in raw meats.
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From page 131... ...
1978 Grade A Pasteurized Milk Ordinance. 1978 Recommendations.
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