Food and nutrition.pdf

MilkPasteurizationPasteurization is used to kill harmful microorganisms by heating themilk for a short time and then cooling it for storage and transportation.Pasteurized milk is still perishable and must be stored cold by bothsuppliers and consumers. Dairies print expiration dates on each container,after which stores will remove any unsold milk from their shelves. In manycountries it is illegal to sell milk that is not pasteurized.lcitation needed]Milk may also be further heated to extend its shelf life through ultrahightemperature treatment (UHT), which allows it to be storedunrefrigerated, or an even longer lasting sterilization process.2311 9 13i:~1 &1= Ct~~~ct .~~_ Cold Water- Heating medium - Ice WaterCreaming and HomogenizationUpon standing for 12 to 24 hours, fresh milk has a tendency to separateinto a high-fat cream layer on top of a larger, low-fat milk layer. The creamis often sold as a separate product with its own uses; today the separationof the cream from the milk is usually accomplished rapidly in centrifugalcream separators. The fat globules rise to the top of a container of milkbecause fat is less dense than water. The smaller the globules, the moreother molecular-level forces prevent this from happening. In fact, thecream rises in cow milk much more quickly than a simple model wouldpredict: rather than isolated globules, the fat in the milk tends to forminto clusters containing about a million globules, held together by anumber of minor whey proteins. These clusters rise faster than individualglobules can. The fat globules in milk from goats, sheep, and water buffalodo not form clusters so readily and are smaller to begin with; cream isvery slow to separate from these milks.Milk is often homogenized, a treatment which prevents a cream layer