FOOD 3090 Study Guide - Food Microbiology, Food Preservation, Water Activity
19 Nov 2014
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Food microbiology and food safety - lecture 5. Food preservation by thermal processing - lecture 6. The product is first frozen and then a vacuum (very low pressures) is used to remove moisture through sublimation (transition of solid water to gaseous water without a liquid phase). The product is porous as the frozen water once occupied space within the product and is now removed without altering the structure of the food material. Depending on the moisture content and structure of the foods, it is very likely that water would migrate from one food item to the other (osmosis) resulting in spoilage of the foods. This can be prevented through the creation of a moisture barrier. This is often achieved using packaging to compartmentalize different foods with differing moisture contents. Another method is to use a food material to create a barrier.
