Talaromyces trachyspermus , A Heat-Resistant Mold Isolated From Fruit Juice

Eight different fruit juices were screened for heat-resistant mold (HRM). Heat was used, in the HRM screening method, to kill nonheat-resistant mold permitting the heat-resistant mold to survive. The HRM screening was beyond the commercial heat processing. An autoclave simplified the screening of large volumes of product and may be a novel use of an autoclave. To increase recovery from heat treatment, the medium was not acidified and surface plating was used in place of pour plating. To reduce cold shock, the product was cooled to ambient temperature and not below. A temperature controlled orbital shaker was used to enhance recovery by increasing aeration and preventing settling. The mold Talaromyces trachyspermus (Shear) Stolk & Samson, previously unreported as an HRM, was detected in retail packaged chilled and frozen pineapple juice but not in other fruit juices. Neosartorya fischeri (Wehmer) Malloch & Cain and Talaromyces flavus (Klöckner) Stolk & Samson were also isolated after a 30-min heat treatment at 80°C. Heat-resistant molds were found in both pure and mixed cultures. T. flavus and T. trachyspermus were growing in a mixed culture after heat treatment.