Microbial Flora of Raw and Pasteurized Egg Albumen

Abstract

Summary Gram negative bacteria were the main spoilage organisms of raw albumen stored at 5, 10, 15 or 20° and were identified as strains of pigmented and nonpigmented Pseudomonas, Acinetobacter and Enterobacter liquefaciens. Only one unidentified Gram negative motile rod which failed to attack glucose was found to survive pasteurization in egg albumen (pH 9‐1) at 57.2° for 3 min. Other Gram negative bacteria isolated from one batch of stored albumen were shown to be heat sensitive, so that recontamination had probably occurred after pasteurization. Most of the organisms which survived pasteurization were found to be faecal streptococci, strains resembling Aerococcus viridans, Microbacterium lacticum and two groups (B and C) of unidentified catalase negative rods, or coccobacilli which in many respects resembled the atypical lactobacilli of Thornley & Sharpe (1959). Of these strains only the faecal streptococci and groups B and C were isolated from stored albumen. The effect of the spoilage flora on the ‘catalase’ activity of albumen before and after pasteurization has been studied in relation to the possibility of a ‘catalase’ test being used to monitor the pasteurization process.

Survival of faecal streptococci in raw and pasteurised egg products

“…The failure of Strep, faecalis strains to multiply in egg albumen prepared aseptically in the laboratory and stored between 5 and 37 °C contradicts the findings of Barnes and Corry (1969) who obtained their samples of albumen from commercial operations. One explanation for the different observations may be that some commercially produced albumen contains enough yolk to support growth of Strep, faecalis.…”

“…Neither can these differences be explained in terms of pH. Commercial samples of egg albumen have a pH of 8-85 to 9-10 ( Barnes and Corry, 1969), while our preparations consistently had a pH of 8-6 which is more favourable for growth. The heat resistance of faecal streptococci is affected by pH, it being highest near neutrality and decreasing rapidly at higher or lower values (White, 1963).…”

“…In eggs stored for periods of up to 10 months high numbers of faecal streptococci were found in the yolk but not in the albumen (Miller, 1954). Faecal streptococci in raw albumen survive pasteurisation for 3 min at 57-2 °G and the survivors then multiply in the product stored for 5 d at 23 C C ( Barnes and Corry, 1969).…”

“…There is no statutory requirement for the pasteurisation of egg albumen although at least 2-5 min at 57-2 °C is recommended. Several types of organisms, including faecal streptococci, have been shown to survive pasteurisation (Barnes and Corry, 1969;Shan et al, 1970;Payne et al, 1979).…”

Occurrence, prevention, and monitoring of microbial quality loss of foods and dairy products

“…Confirmation mostly rests on rapid growth in a rich infusion medium at 45 ± 0.1 °C, leading to short chains of catalase negative cocci. 1606 These criteria are invaluable to recognize colonies of the genus Aerococcus 162 * - 1630 which grows well and typically on BAA-agar, and 54 discard these or take them into account as the ecology of the food requires. Completed evidence can be achieved by checking growth in 40% bile; 1606 identification of isolates rests on the use of the so-called Sherman criteria, summarized in Table 19.…”