The Keeping Quality, Solubility, and Density of Powdered Whole Milk in Relation to Some Variations in the Manufacturing Process. II. Solubility and Density

In judging the quality of whole milk powder, first consideration should be given to palatability.Of almost equal importance for proper consumer acceptance is the solubility of the powder and the ease with which it may be reconstituted. REVIEW OF LITERATURE Solubility.There are many reports which show that the temperature-time relationship of preheating of the milk has a direct relationship to the solubility of the resulting powder.However, it should be borne in mind that solubility is relative and depends upon the solubility test used.Crossley and Johnson (4) concluded that the solubility of milk powder was least impaired when the preheating temperature did not exceed 159 ° F. for 20 seconds.For temperatures of between 150 and 163 ° F. for 20 seconds, followed by a 3 to 5 minute holding period at a slightly lower temperature, the mean solubilities found were nearly a constant value only just below that obtained at 159 ° F.Even at 167 ° F. the reduction in solubility was not of commercial significance.Hollender and Tracy (6) compared the solubility indices of powders made from whole milk preheated at 150, 170 and 190 ° F. for 30 minutes and found that the least soluble powders were those made from the milk preheated at 190 ° F. However, Crossley (3), by using the short-time preheating method, found little loss in solubility in powder made from milk preheated at 190 ° F. as compared to that in powder made from milk preheated at 165 ° F., and the very small loss of solubility appeared to be more than offset by the increased keeping quality with respect to flavor.