A survey on heat-resistant moulds in heat treated milk, milk products and fruit juices

Abstract

Thermal processing of foods leads to the inactivation of most microorganisms but some moulds producing ascospores are able to survive and cause food spoilage. Heat resistant fungi are widely distributed in soil and are consequently associated with spoilage problems in products containing fruits (yoghurt and ice-cream) which are readily contaminated by soil, e. g. strawberry, grapes, and other fruits. Besides fruits, it is known that ascospores of Byssochlamys spp., which is a very common heat resistant mould, have also been found in milk and milk products. In this study, the presence of heat resistant moulds was investigated in heat pasteurised milk, milk products and fruit juices sold in Istanbul. The samples (n = 250) were divided in five groups, pasteurised milk (n = 50), yoghurt (n = 50) and ice cream (n = 50) with fruit, cheese (n = 50) and fruit juices (n = 50). Out of this total of 250 samples 12 (4.8%) were detected as positive for ascospores; of heat resistant moulds. Of the moulds isolated 1.2% and 3.6% were Talaromyces macrosporus and Byssochlamys nivea, respectively.