When it comes to durability of food products, the technology often used the term workmore water is moist content. Two values are related to each other but not the same. Moisture content is the number of grams of water in the 100 grams of product. Activity of the water shall be determined by the ratio between the water equilibrium vapor pressure of that food and water vapor pressure of pure water balance measured at the same temperature. Water activity can be viewed as the availability of water for the growth of micro-organisms and for the chemical reaction or reactions catalyzed by enzymes occurs.The two products have the same moisture content will have the durability of preservation does the same if there is activity in different countries. For example, in the amount of 10% of the moist, powdered milk will spoil very quickly while Soy nuts very durable because the water activity of milk powder will be much higher.The processing process can reduce water activity include drying, condensed, evaporated the water, add the dissolved substance (such as sugar, salt), and conditioning. So the process of such processing increases the product's preservation properties (increase the shelf life of the product).
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