Heat resistance of butyric clostridia responsible for spoilage of acid products.

摘要

Studies were conducted on heat resistance of 4 strains of butyric clostridia isolated from diced peaches, acidified mushrooms in oil, tomato paste, and pear juice. The strains included 2 ascribable to Clostridium pasteurianum, 1 attributable to C. beijerinckii and 1 ascribed to C. tyrobutyricum. The isolates were made to sporulate in field soil. Heat resistance was determined in tomato juice (pH 4.2 or 4.5), pear puree (pH 3.9) and peach juice (pH 3.6). In tomato juice, heat resistance decreased with decreasing pH of the medium. The 2 C. pasteurianum strains had considerably higher heat resistance than the other 2 strains; at pH 4.5, D-values were 35.46 and 41.15 min for the C. pasteurianus strains, vs. 5.8 min for the C. tyrobutyricum strain and 6.8 min for the C. beijerinckii strain. The z-value was approx. 5°C for the 2 C. pasteurianus strains and 10-12°C for the other 2 strains. Heat resistance trials in pear puree and peach juices were conducted only with the 2 C. pasteurianus strains. D-value for 1 strain was 24.69 min in pear puree and 19.76 min in peach juice; D-values for the other stain were 10.44 min in pear puree and 9.13 min in peach juice. The z-value was approx. 5°C for 1 C. pasteurianum strain, and almost 10°C for the other. These results are discussed in relation to literature data.