NU FS100 Lecture Notes - Lecture 3: Spray Drying, Case-Hardening, Freeze-Drying
Document Summary
Three common drying methods: heat alone, spray drying, freeze drying. P = t bp bp: vacuum drying remove water from the product at lower temp. under partial vacuum. As a product dries, its free water is removed. Some water is held by absorption to food solids: water chemically bound in the form of hydrates is hardest to remove, water is dif cult to remove too when interacting with, high amounts of sugar, starch, pectin, gums. Other changes: loss of ease of rehydration (d/t denatured proteins and loss of sugars and salts, altered texture, harder (meat) vs softer (onions, loss of avour. Radiant heat evaporates water: old technique used in warm, dry climates, inexpensive but slow, risk on invasion by insects, bird etc. Hot air in a closed environment supplies heat by convection. Fluid foods are sprayed into a steam of hot air: liquid products, ex: milk, eggs, protein powders, avors, coffee, fast method to dehydrate.