Effect of processing and storage on the reconstitution properties of whole milk and ultrafiltered skim milk powders : thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Food Technology
The climates of many areas in Asia, Central America, the Middle East and Africa make it difficult to support a dairy industry based on fresh milk. In these areas the shelf life of fresh, undried milk products is short. Concentrated and dry milk products have increased storage stability because of a lower water activity and are therefore desirable in regions with such climatic conditions. Concentrated milk products are obtained from milk by the application of one or a combination of water removal techniques. Drying of these products can reduce the water content to below 3%. The reduction in water content of milk will increase shelf life and reduce transportation costs. This is particularly important for manufacturers that export products to distant markets. These products may be recombined (water and a combination of ingredients added) or reconstituted (just water added) and then packed and sold by a food retailer, or sold directly to the consumer as a dry or concentrated product, e.g. whole milk powder (WMP) or canned evaporated milk. The range of concentrated and spray-dried dairy powders commercially produced today is wide and includes ultra-high-temperature (UHT) treated concentrated milks, in-can sterilised milks, skim milk powder, WMP, formulated infant food powders, high protein powders and high fat powders, whey powders, buttermilk powders, cream powders, casein and caseinates. Lately, membrane technology, e.g. ultrafiltration, has improved and applications have been developed for many processes leading to the production of a new range of concentrated and dried products, e.g. milk protein and whey protein concentrates.