Studies on Minerals of Milk and Milk Products

I. Sodium and-Potasaium contents in milk ash

Abstract

During a period of 1957 to 1960, 106 samples of market milk, 83 of composite raw milk, and 71 of individual raw milk were collected monthly from various milk plants and regions and 5 Holstein cows. These and 22 samples of whole-milk and skim-milk powder, which had been manufactured at various areas in Japan in different seasons, were examined for mineral contents.
The samples were ignized at 55-600°C and 13 elements, K, Na, Ca, Mg, P, Si, Zn, Sn, Cu, Mo, Mn, B, and Al, were identified as normal constituents by the arc method. The amounts of these elements were estimated.
At first, K and Na were determined by the flame photometric method and their regional, seasonal, and individual variations were considered. The K contents of individual raw, compositeraw, and market milk, and skim-milk and whole-milk powder were 230.68 (n=71), 216.75 (n=83), 201.33 (n=106), 234.37 (n=15), and 228.38 (n=7)mg per g of ash, respectively. The Na contents of the same milk and milk products were 80.38 (n=71), 75.50 (n=82), 72, 03 (n=105), 67.47 (n=15), and 70.62 (n=7)mg per g of ash, respectively.
The K contents of milk ash were smaller in late winter and early spring than in the other seasons. The highest level of this element was reached from summer to early autumn. The low level of K in early spring was caused by an increase of late-lactation-period milk. During the last two months of the lactation period, K contents rapidly decreased, as shown in fig. 1. On the other hand, Na contents increased gradually. Therefore, seasonal changes were not somarked in Na contents as in K contents. Regional and individual differences, however, werelarger in Na contents than in K contents.
When stochasticalby considered, the correlation coefficient between the K and Na contents. of raw milk was negative (p<0.05) and that of powdered milk was insignificant.