Extraordinary Heat Resistance of Talaromyces flavus and Neosartorya fischeri Ascospores in Fruit Products

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  • LBL. R. Beuchat
    L. R. Beuchat
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Abstract
Ascospores of three strains each of Talaromyces flavus, Neosartorya fischeri and Byssochlamys fulva/nivea were analyzed for resistance to thermal inactivation in five fruit‐based (blueberry, cherry, peach, raspberry and strawberry) products. D 91°C values for two strains of T. flavus ranged from 2.9–5.4 min; D 88°C values ranged from 7.1–22.3 min. Ascospores of N. fischeri were somewhat less heat resistant; D 91°C values were < 2.0 min and D 88°C were 4.2–16.2 min. Ascospores of Byssochlamys spp. were considerably less heat resistant. The type of fruit product did not appear to substantially influence rates of thermal inactivation. No heat‐resistant ascospores of T. flavus or N. fischeri , i.e., ascospores capable of surviving 15 min at 75°C, were formed on fruit products stored at 10°C for 137 days. However, T. flavus and N. fischeri formed ascospores on cherry substrate stored at 25°C within 65 and 137 days, respectively, that survived 15 min at 88°C.