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Fundamental Food Microbiology, Third Edition - Fuad Fathir

Fundamental Food Microbiology, Third Edition - Fuad Fathir

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NEW FOOD SPOILAGE BACTERIA IN REFRIGERATED FOODS 295<br />

Figure 20.1 Bacterial spoilage of vacuum-packaged refrigerated foods. (A) Spoilage of beef<br />

by Clo. laramie: left, a spoiled sample showing gas accumulation; right, an<br />

unspoiled sample. (B) Spoiled tofu by a Clostridium sp. showing accumulation of<br />

liquid and gas. (C) Spoiled frankfurters and (D) spoiled luncheon meat predominantly<br />

by Leuconostoc spp. showing gas accumulation. (E) Spoiled sliced turkey<br />

roll by heterofermentative lactobacilli, leuconostocs, and Ser. Liquifaciens: right,<br />

gas accumulation (and pink discoloration); left, an unspoiled sample. (F) Spoilage<br />

of ground beef chub by heterofermentative lactobacilli showing gas accumulation.<br />

B. Spoilage of Roasted Beef by Clostridium ssp.<br />

Clostridium spp. have been isolated from at least two separate incidents of largescale<br />

spoilage of vacuum-packaged refrigerated roasted beef produced commercially.<br />

The meats (10 to 12 lbs [4.5 to 5.5 kg] each) were roasted £ 160�F (71°C) (internal<br />

temperature) and then vacuum-packaged and refrigerated. 6,8 When the samples were<br />

received in the laboratory, they had large quantities of gas and purge but, because<br />

of the spices used in the meat, only a strong spicy smell was evident. Phase-contrast<br />

microscopy of the purge revealed large numbers of motile Clostridium cells, some<br />

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