Effects of heat treatments and subsequent storage on the mineral balance of ewes' milk

Abstract

The effects of heat treatment of ewes' milk at 65–85°C for 10–30 min and subsequent storage at 20°C for 90 min on the changes in ionic calcium and the distribution of calcium, magnesium and phosphorus between the diffusible and micellar phases were studied. As milk was heated there was a decrease in ionic calcium of ∼36 mg/l, but there was a rapid 86–90% recovery during the first 30 min after heating. Although the rate of reversal on subsequent storage decreased with the intensity of the heat treatment, there were no significant differences between samples after 90 min storage. Similar results were obtained for cows' milk subjected to the same treatments. Diffusible calcium, magnesium and phosphorus in heated samples were lower than in raw milk. Recoveries of initial values decreased with the severity of the heat treatment and were 80–95% for calcium, 85–97% for magnesium and 87–98% for phosphorus. Heat treatment under milder conditions (85°C for 20 s) was associated with almost complete recoveries. Recoveries of the minerals studied were slightly lower in ewes' than in cows' milk.