Food drying and evaporation_0915

Food drying and evaporation_0915 - Food Drying and...

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Food Drying and Evaporation Drying Drying is a method of food preservation that works by removing water from the food. Foods are dried to inhibit microbial development and quality decay, and assist in saving transportation and storage costs. Methods of drying Natural air drying . The process is slow and weather-dependent. It is often used for drying grains. Hot air drying. Spray drying is a sample. Indirect or contact drying (heating through a hot wall), e.g. drum drying, Freeze drying or lyophilization is a drying method where water is frozen prior to drying and is then sublimed, i.e., passed to the gas phase directly from the solid phase, below the melting point of water. Supercritical drying involves high-temperature and high-pressure. The route from liquid to gas does not cross any phase boundary, instead passing through the supercritical region, where the distinction between gas and liquid ceases to apply. This process is most commonly used to transform gels into aerogels. Spray drier drum drier Example 1. Heat energy in air drying Food material containing 80% water is to be dried at 100°C down to moisture content of 10%. If the initial temperature of the material is 21°C , calculate the quantity of heat energy required per unit weight of the original material, for drying under atmospheric pressure. The latent heat of vaporization of water at 100°C at standard atmospheric pressure is 2257 kJ kg -1 . The specific heat capacity of the material is 3.8 kJ kg -1 °C -1 and of water is 4.186 kJ kg -1 °C -1 . 1.
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Food drying and evaporation_0915 - Food Drying and...

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