4 14 14 Lecture 18 Food Dehydration and Concentration Drying Milk Spray Drying Milk DVD Notes Thorough inspection of quality control when milk arrives at plant samples are taken for testing 2 main tests are run 1 microbial tests to make sure no microorganisms in milk 2 antibiotic testing also look at protein fat and solids content Once milk is approved by quality control then the ok is given for milk truck to continue through the next step to the plant aseptic process milk being pumped out goes into fluid silos 60 000 pounds of milk in large silos 40 000 pounds in smaller silo each silo has an individual opening into the plant silos are kept refrigerated takes 10 semi loads to fill one silo all plumbing stainless steel only type approved by FDA important to clean and sanitize truck before and after CIP cleaning in place Milk that is washed out of the truck is moved into a lagoon and goes through degradation releasing only pure water into local streams Steps of Drying Step 1 separation and pasteurization pass whole milk through separator going to dry full fat milk so move milk directly Step 2 High Temperature Short Time HTST 161 degrees F at 15 s to destroy microorganisms milk falls down a column that acts as a vacuum that sucks the vapor up and off the milk milk fats at bottom of uses vacuum evaporator compressor heats and moved water vapor up and through ducts air reheats the new milk coming in high pasteurized milk at 12 solids comes in at 50 solids by a multistage evaporator Step 3 Homogenization condensed milk is dried at very high temperatures pushed out with high pressure pushed up to top of the plant hot homogenized milk ready to be dried Step 4 Spray Drying homogenizer pushes the hot milk up to the dryer spray dryer can be visibly seen outside of plant tornado of hot air and the milk mixing those that dry rapids that are being pulled off through tube on the side of dryer vacuum cleaner type part that pulls out the vapor not all particles are dry at the same time continue to dry and fall at cone shaped dryer at the bottom milk blown out of bag house into system of tubing hopper collects the dried milk Step 5 Packaging and Transport milk then tested for quality control e g microbes once passes inspection goes to another hopper prevent milk from sticking by vibrating tube the milk in semi can hold 44 000 pounds of the dried milk powder in truck produced over 2 day process