FOOD PROCESSING AND PRESERVATION
DRYING AND DEHYDRATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which of the following is incorrect about Water activity or aw?
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Relative humidity over feed at equilibrium divided by 100.
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The vapor pressure of the food water divided by the vapor pressure of the pure water.
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lower than 0.6 = almost of microbial is inhibited
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lower than 0.9 = almost of bacteria is inhibited
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Fresh food aw lower than 0.85
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Explanation:
Detailed explanation-1: -Measuring water activity (aW) The water activity scale extends from 0 (bone dry) to 1.0 (pure water) but most foods have a water activity level in the range of 0.2 for very dry foods to 0.99 for moist fresh foods. Water activity is in practice usually measured as equilibrium relative humidity (ERH).
Detailed explanation-2: -Higher water activity substances tend to support more microorganisms; bacteria usually require water activity values of at least 0.91 and fungi at least 0.6.
Detailed explanation-3: -Dried beans, rice, sugar, and salt also stay edible for years because of a common trait – low levels of water activity.
There is 1 question to complete.