Significance of milk fat in milk powder

Abstract

The production of milk powder involves dehydration via evaporation and spray drying, followed by packaging and storage. The two principal types of milk powders produced directly from milk or skim milk are whole (full-cream) milk powder (WMP) and skimmed milk powder (SMP; or non-fat dry milk, NDM). There are three types of SMP-low-heat, medium-heat, and highheat-that are classiWed based on the level of undenatured whey proteins (whey protein nitrogen, WPN index), which is a direct result of the level of heat treatment given to milk/concentrate during powder manufacture. The WPN index for low-heat, medium-heat and high-heat powders is, respectively, 6:0, 1.51-6.0 and 1:5mg WPN/g (ADPI, 2002). Other dried milk products containing fat are buttermilk powder (BMP), fat-Wlled milk powder, cream powder, retentate powder, and cheese powder. The majority of milk powder produced worldwide is in countries with a temperate climate and a relatively large dairy industry. The powder is exported mostly to tropical and developing countries in which the dairy industry is not well developed and facilities for cooling and handling fresh milk are inadequate. In milk powderproducing countries, some of the milk powder is used in a variety of dairy and food applications (e.g., ice cream, cheese, infant formulae, evaporated milk, sweetened condensed milk). Milk powder is also used as an ingredient in bakery products, processed meats, soups, etc. The function of milk powder in these products is inXuenced by the components of the powder, primarily protein (casein or whey proteins), fat and lactose. The signiWcance of milk fat in milk powder is the subject of this review, and it is focused on WMP. Figure 13.1 is a Xow diagram for the traditional processes for the manufacture of WMP, SMP, and BMP. An alternate process for the manufacture of WMP that involves blending highly heated cream and low heattreatedskim milk concentrate prior to drying, was described by Hols and Van Mil (1991). The recommended standards for WMP, SMP and BMP, as well as average composition of the powders, are shown in Table 13.1.