Solubility, milk powder

An immunoassay was developed to determine the penicillinase stable isoxazolyl penicillins cloxacillin and dicloxacillin in milk by Usleber et alJ The assay detected lOpgkg" of cloxacillin and 30pgkg of dicloxacillin with recoveries of 102% and 84%, respectively. The calibration curve was prepared by fortifying skimmed milk powder (lOOgL ) with standards. Fortified samples were prepared in pasteurized milk and analyzed directly after decreaming by centrifugation. This immunoassay was performed with minimal sample preparation, probably because the extensive water solubility of the penicillins prevents problems associated with more lipid-soluble analytes. 

Traditionally, milk was paid for mainly on the basis of its fat content but milk payments are now usually based on the content of fat plus protein. Specifications for many dairy products include a value for protein content. Changes in protein characteristics, e.g. insolubility as a result of heat denaturation in milk powders or the increasing solubility of cheese proteins during ripening, are industrially important features of these products. 

Casein can be precipitated from solution by any of several salts. Addition of (NH4)2S04 to milk to a concentration of 260 g 1 1 causes complete precipitation of the casein together with some whey proteins (immunoglobulins, Ig). MgS04 may also be used. Saturation of milk with NaCl at 37°C precipitates the casein and Igs while the major whey proteins remain soluble, provided they are undenatured. This characteristic is the basis of a commercial test used for the heat classification of milk powders which contain variable levels of denatured whey proteins. 

M. C. Yebra, A. Moreno-Cid, R. Cespon and S. Cancela, Preparation of a soluble solid sample by a continuous ultrasound assisted dissolution system for the flow-injection atomic absorption spectrometric determination of iron in milk powder and infant formula, Talanta, 62(2), 2004, 403 406. 

As mentioned previously, alcohol greatly reduces the solubility of lactose, but the glass or amorphous form dissolves in alcoholic solutions to form supersaturated solutions. This has been used to extract lactose from whey or skim milk powder with methanol or ethanol. A high-grade lactose subsequently crystallizes from the alcoholic solu-... 

Leviton, A. 1949. Methanol extraction of lactose and soluble proteins from skim-milk powder. Ind. Eng. Chem. 41, 1351-1357. 

Howat, G. R. and Wright, N. C. 1937. Factors affecting the solubility of milk powders. III. Some physico-chemical properties of concentrated solutions of milk solids. J. Dairy Res. 5, 236-244. 

Spray drying per se has little effect on the chemical and physicochemical properties of milk powder when the severity of heat treatments has been minimized (Parry 1974). The solubility of the milk powder product is controlled by altering the temperature and time of heat treatments... 

EJ de Vries, B Borsje. Analysis of fat-soluble vitamins. 27. High performance liquid chromatographic and gas-liquid chromatographic determination of vitamin D in fortified milk and milk powder collaborative study. J Assoc Off Anal Chem 65 1228-1234, 1982. 

Lange, P. de. Decrease of solubility and nutritive value of milk powder during storage. Conserva 1954, 2, 322-5 ... 

Hibbs, R.A., Ashworth, U.S. 1951. The solubility of whole milk powder as affected by protein stablizers and emulsifiers. J. Dairy Sci. 43, 1084-1086. 

Powder characteristics of a physico-chemical nature, such as solubility, wettability, dispersability, and measures of the instant properties of powders (sludge, slowly dispersible particles, hot water sediment and coffee test), are determined by a variety of empirical physical tests, some of which incorporate subjective elements. These and the other tests for whole milk powders identified above are described in detail by Westergaard (1994) and Pisecky (1997). 

Williams, R.P.W., D Ath, L., and Augustin, M.A. (2005). Production of calcium-fortified milk powders using soluble calcium salts. Lait, 85, 369-381. 

Baked foods, instant foods, milk powders Salad dressings, release water-based flavor, colors Instant foods. Flavors Cosmetics and soaps, dyes, leather Oil soluble, water dispersible Oil soluble, water dispersible Easily sprayable, low viscosity, water dispersible - - - X X - X - - - X X - X - X X X... 

High-protein powders are generally more difficult to reconstitute compared to conventional skim milk powder ( 34% protein), and the problems of reconstitution are worse with increasing protein content. The solubility of the MFC powders deteriorates further during storage. MFC powders with improved solubility are made by the addition of monovalent salts to the ultrafiltered retentate (Carr, 2002) or by the removal of calcium ions prior to drying (Bhaskar et al., 2003). 

Rodriguez del Angel, C., and Dalgleish, D.G. (2006). Structures and some properties of soluble protein complexes formed by the heating of reconstituted skim milk powder. Food Res. Int. 39,472-479. 

When the product coming out of the spray dryer is too fine it does not wet readily and so is harder to reconstitute. To make the product more readily soluble, it is agglomerated in a small fluidized or vibrated fluidized bed, as shown in Figure 23.23. This two-stage arrangement is used in the production of instant coffee, milk powder, cocoa, etc. An extension of this basic concept is the so-called spray-fluidizer, which dries the material in two stages. In the first stage (spray dryer). 

The solubility of soybean extract, soybean flour, and milk powder had a positive influence on the results from SmF. For milk powder, the higher amount of water decreased the damaging effects of sterilization, especially regarding the texture, increasing enzyme production. 

Electrostatic interactions in air are very different compared to the electrostatic interactions in aqueous systems, as there is no ion solubility and no double layer is formed. The source of the surface charges is also different. In air, there are no possibilities for acid-base interactions or for ion disassociation. Charging in air is caused by static electricity and is stable for non-conducting particles. This makes the interaction coulombic in nature, with a range comparable to the radius of the particle. The electrostatic interactions easily dominate when the particle size is large, the density is low, and there is a low water content (low conductivity). Typical examples could be during the drying of milk powder or the transport of coffee powder. 

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