Heat-resistance of Hamigera avellanea and Thermoascus crustaceus isolated from pasteurized acid products

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• 作者：Nicoletta Scaramuzza ; Elettra Berni
• 关键词：Hamigera avellanea ; Thermoascus crustaceus ; Heat resistance ; Blueberry and grape juice ; Apple juice
• 刊名：International Journal of Food Microbiology
• 出版年：3 January, 2014
• 年：2014
• 卷：168-169
• 期：Complete
• 页码：63-68
• 全文大小：383 K

文摘

Products containing sugar or fruit derivatives are usually subjected to a pasteurization process that can anyway be ineffective to kill ascospores from heat-resistant molds. Although the most occurring and economically relevant heat-resistant species belong to Byssochlamys, Neosartorya, Talaromyces, and Eupenicillium genera, an increasing number of uncommon heat-resistant isolates have been recently detected as spoiling microorganisms in such products. Since Hamigera spp. and Thermoascus spp. were those more frequently isolated at SSICA, heat resistance of Hamigera avellanea and Thermoascus crustaceus strains from pasteurized acid products was studied in apple juice, in blueberry and grape juice and in a buffered glucose solution. Data obtained from thermal death curves and statistical elaboration of raw data showed that D values of H. avellanea may vary between 11.11 and 66.67 min at 87 掳C, between 4.67 and 13.51 at 90 掳C, and between 0.43 and 1.52 min at 95 掳C. Similarly, D values of T. crustaceus may vary between 18.52 and 90.91 min at 90 掳C, between 2.79 and 19.23 at 93 掳C, and between 1.11 and 2.53 min at 95 掳C. For both strains studied, the z-values calculated from the decimal reduction time curves did not prove to be significantly influenced by the heating medium, that being 4.35 掳C, 5.39 掳C or 5.27 掳C for H. avellanea and 4.42 掳C, 3.69 掳C or 3.37 掳C for T. crustaceus, respectively in apple juice, in blueberry and grape juice or in the buffered glucose solution.

Considering the pasteurization treatments industrially applied to fruit-based foods, the variation of thermal parameters does not seem to be a possible way to avoid product spoilage by these two species and only good practices applied to reduce the original load of heat-resistant fungi can help producers to prevent losses in contaminated finished products, as usually happens for other heat resistant molds.