ENH 333 Lecture Notes - Lecture 4: Food Preservation, Zygosaccharomyces, Shelf-Stable Food
11 Oct 2018
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Document Summary
Drying: the most ancient method of food preservation, foods that are dried have a lower aw than fresh and therefore microorganisms cannot grow or grow more slowly. No spoilage or increase in hazard: earliest method involved exposure to sunlight, modern drying techniques include spray, drum, evaporation and freeze-drying. E. g. evaporated milk is produced using drum/spray drying removing 60% of water and increasing the final sugar concentration: foods usually require pre-treatment (e. g. cooking for meats, blanching for vegetables) Low moisture foods (lmf) are those with a aw of 0. 0 0. 6. E. g. spaghetti (0. 39), cereals (0. 15-0. 4), instant coffee (0. 17) They are shelf stable (i. e. can be stored at ambient temperatures) Require appropriate rh conditions otherwise the aw will rise and spoilage / microbial growth will occur. Intermediate moisture foods (imf) are also shelf-stable and have aw values of 0. 6 . E. g. dried fruits (0. 6-0. 75), cakes / pastries (0. 6-0. 9), jams (0. 8-0. 9)
