Fundamental Food Microbiology, Third Edition - Fuad Fathir

NEW FOOD SPOILAGE BACTERIA IN REFRIGERATED FOODS 303
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Table 20.3 Spoilage Characteristics of Some Predominant Bacteria in Vacuum-
Packaged Refrigerated Foods
Spoilage Characteristicsa Cell Morphologyb Most Likely Bacteriac Large volume of gas and
purge, no H2S, not much offodor,
purge pH £ 5.5
Little gas and purge, no H2S, not much off- odor, purge
pH £ 5.
Large gas, little purge, H2S +/–, off-odor, purge pH £ 6
Little gas and purge, NH3 odor, purge pH � 7.5
Little gas and purge, putrid
odor, purge pH � 8.0
Large volume of gas and
purge, H2S odor, purge pH
� 7.5
Coccoid to lenticular, small
chains, Gram +ve
Rods, some in chains,
nonmotile, Gram +ve
REFERENCES
Leuconostoc spp.
Homofermentative
Lactobacillus spp.
Rods, some in chains, Heterofermentative
nonmotile, Gram +ve Lactobacillus spp.
Small rods, motile, Gram –ve Serratia spp.
Small rods, motile, Gram –ve Hafnia, other
Enterobacteriaceae
Thick rods of different sizes, Psychrotrophic Clostridium
motile, some with terminal spp.
spores, Gram +ve
a There are some characteristics commonly found in the early stage of spoilage of a product.
However, a sample can be spoiled by more than one type, especially in the early stages
and can show mixed characteristics.
b Morphology is examined with a drop of purge under a phase-contrast microscope. With
practice, an almost presumptive positive identification can be made in minutes.
c Except for spores of Clostridium spp., all are sensitive to low-heat treatments
(pasteurization). Their presence in heated products results mostly from postheat
contamination and on the product surface.
1. Kraft, A.A., Psychrotrophic Bacteria in Foods, Disease and Spoilage, CRC Press,
Boca Raton, FL, 1992, p. 3.
2. Olson, J.C., Jr. and Nottingham, P.M., Temperature, in Microbial Ecology of Foods,
Vol. 1, Silliker, J.H., Ed., Academic Press, New York, 1980, p. 1.
3. Ray, B., The need for food biopreservation, in Food Biopreservatives of Microbial
Origin, Ray, B. and Daeschel, M.A., Eds., CRC Press, Boca Raton, FL, 1992, p. 1.
4. Ray, B., Foods and microorganisms of concern, in Food Biopreservatives of Microbial
Origin, Ray, B. and Daeschel, M.A., Eds., CRC Press, Boca Raton, FL, 1992, p. 25.
5. Ray, B., Kalchayanand, N., and Field, R.A., Meat spoilage bacteria: are we prepared
to control them?, Natl. Provision., 206(2), 22, 1992.
6. Kalchayanand, N., Ray, B., and Field, R.A., Characteristics of psychrotrophic
Clostridium laramie causing spoilage of vacuum-packaged refrigerated fresh and
roasted beef, J. Food Prot., 56, 13, 1993.
7. Collins, M.D., Rodrigues, U.M., Dainty, R.H., Edwards, R.A., and Roberts, T.A.,
Taxonomic studies on a psychrophilic Clostridium from vacuum-packaged beef:
description of Clostridium estertheticum sp. nov, FEMS Microbiol. Lett., 96, 235,
1992.
8. Ray. B., Kalchayanand, N, Means, W., and Field, R.A., Spoilage of vacuum-packaged
refrigerated fresh and roasted beef by Clostridium laramie is real. So are other
spoilage bacteria in processed meat products, Meat Poult., 40(7), 12, 1995.