THE INFLUENCE OF MINERALS AND LACTOSE CONTENT ON THE STABILITY OF WHEY PROTEIN POWDERS

The aim of this paper was to determine the minerals and lactose from a Zonar lactoserum concentrate (L-ZS) obtained by lyophilization as compared to other two commercial powders: a bio whey concentrate (BWP) and a whey protein isolate (IWP), in order to investigate the influence of the mineral and lactose concentration on the protein denaturation temperature. The BCAA content from protein hydrolysates and surface structure of whey powder samples have been also investigated. Lactose content of samples whas: 47.4 g/100g for L-ZS, 46.4 g/100g for BWP, 0 g/100g for WPI. The highest concentrations of minerals Ca, K, Mg, Na and P has been found in BWP, followed by, L-ZS and IWP powders. The fact that L-ZS sample shows a peak temperature (Tp) with 15.82 degrees C higher than in the case of BWP sample, makes it more resistant to denaturation. The IWP powder has Tp of 87.25 degrees C, because contains the high quantity proteins that are more resistant to unfolding (denaturation) than the other two samples. Loss of calcium ions leads to partial protein unfolding. The lower mineral content increases the stability of whey protein. A high lactose content leads to the protein aggregation; the functional properties of powder is changes by protein crosslinking. Branched-chain amino acids content in studied samples is in accordance with whey proteins powders type.