The Phoenicians built appropriate facilities for salting and drying fish, dried vegetables, cured meats or make powdered milk. These methods have been used traditionally to prolong the life of food, centuries before it was discovered Pasteurization.
Importance of water.
Water is perhaps the most essential for life as we know it. Microorganisms can grow in a very wide range of temperatures and environments … But they can not grow without water. If a food we remove the water available will cease to be attractive to microorganisms.
Humans can survive a week without eating, however, after several hours without ingesting liquid begin to notice symptoms of dehydration.
Duration of foods by water activity.
The water contained in food is essential to relate to the duration of these.
The concept, in particular, is called water activity (aw). This is the amount of free water in the food and is provided in a ratio of 0 to 1, where 1 means that 100% of the food is water.
Decreasing the water activity of a food, this is dried and texture thereof hardens, becomes more crunchy and brittle.
The lower the water activity of a food, the higher its life, since it becomes less attractive for the majority of microorganisms, which do not degrade the food. Therefore, foods with low water activity (aw less than 0.60) will not suffer microbial degradation, while another may contain bacteria such as resident (not degrade the food) and some fungi.
Ways to reduce the free water in a food.
There are two ways of reducing water from a food:
– Drying, which involves evaporation of water-free food. Examples are those used in dried fish, vegetables, fruit or milk.
– The other method is to add salt or sugar. In this case no water is removed from food, but it decreases the water available, because the feed water molecules surrounds the salt or sugar and no longer available for microorganisms.
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