243. Factors affecting the solubility of milk powders. IV. The influence of speed and duration of stirring on solubility, with a description of a rapid method for solubility determinations

Abstract

1. The effects of alterations in the duration and speed of stirring on the apparent solubility of milk powders have been investigated. It is concluded that 30 sec. shaking of the powder reconstituted in a 10 % mixture is sufficient to dissolve the truly soluble portion of the dried milk, but that the protein which has become denatured during the drying process tends to pass into solution with increasing speed and duration of stirring.2. A rapid method for estimating the solubility of milk powders on a total solids basis involving only 1 min. shaking is described and discussed.3. The sediment method frequently used in industry as a guide to the solubility of dried milks is compared with the rapid method described in the present paper. At higher solubilities the sediment volume may serve as a guide to small changes in solubility, but in the lower solubility ranges its usefulness is very limited. It is shown that the washing of the sediment with one or more changes of water merely introduces additional errors into this method of solubility determination.