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Lesson_11_ Outline_dehydration - Challenges in food...

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1. Food dehydration (defined) removal of water from foods under controlled conditions. Drying stops microbial growth and chemicla and enzymatic reactions. 2. Heat and mass transfer considerations Surface area: rapid drying will be enhanced by a large surface area, small pieces, or thin layers Temperature: warmer air will speed the rate of heat transfer into the food; providing the driving force for moisture removal. HTST is best Air velocity; heated air takes up more moisture and sweeps moist air away from the surface of a food product humidity; the drier the air, the more rapid the rate of drying. 3. Sun drying large nutrient cost associated with method. Risk of insect infestation 4. Tray or tunnel drying warm dry air goes over food in production 5. Spray drying like the mac and cheese powder. Hot dry air (350 degrees C). 6. Drum drying heated rollers move toward each other, rapidly drying thick pastes or slurries. 7. Freeze drying 1
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Unformatted text preview: Challenges in food dehydration non-homogeneous food matrix: it can be difficult to adjust the drying process for all components solute concentration: foods high in sugar or salt tend to hold tightly to water inter and intracellular water: location of water within and between tissue cells can make moisture removal challenging. Case hardening : an impenetrable skin or film forms on the surface of a food, preventing moisture from leaving 9. Stability of dried food Dried foods are hydroscopic meaning they tend to pick up moisture from the air to regain what has been lost. Proper packaging is one of the best ways to prevent moisture uptake by dehydrated or dry foods. Microorganisms can survive the drying process and cause illness or spoilage if food is not properly handled. And from a nutrient standpoint, we must remember that foods with water removed become a concentrated source of nutrients. 2...
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