E. RAJASHEKHARA, E.R. SURESH AND s. ETHIRAJ. 1996. A heat-resistant mold identified as a strain of Neosartorya jischeri was isolated from microbiologically spoiled papaya fruits. The optimum heat activation temperature and time for the ascospores of the test mold was found to be 80°C for 15-30 min. The decimal reduction times (D-values) at 85", 87" and 89°C in phosphate buffer (pH 7.0) as heating medium were 35.25, 11.1 and 3.90 min respectively and hence the calculated z-value was 4.0"C. In grape and mango juices as heating media, the D,,oc and the DsjOc values were increased as the "Brix level raised from 10 to 45. In commercial fruit juices of mango, orange, pineapple and mango-pineapple blend as heating media DRsOc values were greater than those observed for phosphate buffer.

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Heat-resistant molds, including Neosartorya fischeri, are known to spoil thermally processed fruit products. The control measures required for such problems must not cause an appreciable loss of the organoleptic qualities of the final products. In the present study we determined the thermal death rates of ascospores of N. fischeri ATCC 200957 in fruit juices containing organic acids and preservatives. The ascospores were able to survive for more than 6 h of heating at 75 degrees C, 5 h at 80 degrees C, and 3 to 4 h at 85 degrees C in mango or grape juice. Of the four organic acids tested, citric acid exhibited the maximal destruction of ascospores in mango juice at 85 degrees C (1/k = 27.22 min), and tartaric acid the least (1/k = 61.73 min). The effect of common preservatives on the thermal death rates of ascospores at .85 degrees C in mango and grape juices was studied. Almost similar effects on thermal inactivation of ascospores were noted when potassium sorbate (1/k = 29.38 min) or sodium benzoate (1/k = 27.64 min) or the combination of both (1/k = 27.53 min) was used in mango juice. In grape juice, potassium sorbate (1/k = 25.07 min) was more effective than sodium benzoate (1/k = 50.08 min) or the combination of both (1/k = 40.79 min) in inactivation of ascospores of the mold. The thermal death rate (1/k) values in mango and grape juices in the absence of any preservative were 63.51 and 69.27 min respectively.

Six morphologically different groups of yeasts comprising Kloeckera apiculata. Candida krusei, Candida valida, Candida sorbosa, Metschnikowia pulcherrima and Saccharomyces chevalieri were isolated from fresh, fermenting and fermented apple juice. This is the first report on the isolation of C. valida, C. sorbosa and S. chevalieri from fermenting and fermented apple juice.