Some yeasts and moulds grow very well at low temperatures
The growth of many microorganisms, including fungi, is slowed or completely inhibited at low (e.g. refrigeration) temperatures. However, some moulds have been reported to grow at temperatures below freezing. These include a large number of foodborne species from the genera Penicillium, Fusarium, Alternaria and Cladosporium. Consequently, potential growth and spoilage by these moulds is very relevant to foods stored at chill temperatures. Our recent research has begun to characterise some Penicillium species that may be particularly worth watching.
Potentially serious spoilage repercussions
Nine strains of Penicillium strains were placed into 2 groups based on their growth behaviour following 'training' to grow at progressively lower temperatures: Group (a) isolates were able to grow more quickly at 0°C compared to 2°C; Group (b) isolates were able to grow more slowly at 0°C compared to 2°C. A biochemical mechanism for the behaviour of Group (a) isolates is suggested, based on glycerol and trehalose (providing protection to low temperatures) working in conjunction with heat shock proteins. The ability of moulds to be able to grow and sporulate at low temperatures has potentially serious spoilage repercussions for manufacturers of chilled and frozen foods. It places more emphasis on the requirement for maintaining clean environmental conditions in the food factory, and preventing opportunities for cross–contamination by moulds.
Members can obtain an electronic copy of the full report (Fungal behaviour at cold temperatures - R&D Report 302) by sending an e–mail to firstname.lastname@example.org with the subject line: send RD302
Contact: Phil Voysey