Heat resistance of Byssochlamys nivea, Byssochlamys fulva and Neosartorya fischeri isolated from canned tomato paste

Cultures of heat resistant molds (20) were isolated from spoiled canned tomato paste in order to estimate the pasteurization efficiency applied to commercially canned products. Ascospores of nine strains grown on mall extract agar for 30 days at 30 degrees C, survived heating at 85 degrees C for 20 min when initial numbers were near 10(5)/mL. Of these heat resistant strains were identified: two Byssochlamys nivea, three Byssochlamys fulva and four Neosartorya fischeri strains. Ascospores of all cultures were more heat resistant in tomato juice than in phosphate buffer. Thermal death rate curves were nonlogarithmic but approached logarithmic death rates at higher temperatures. The thermal destruction time for 1 log(10) at 90 degrees C was 1.5 min for a Byssochlamys nivea strain, 8.1 min for a Byssochlamys fulva strain and 4.4 to 6.6 min for Neosartorya fischeri strains.