The study of physical properties of spray dried whey and milk permeates lactose
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The aim of this study was to investigate substrate and environment effect on the physical state of lactose crystals, their stability and behaviour comparing with pure lactose which traditionally used in an analysis. Sweet and acid whey permeate as well as milk permeate were analysed. Mini spray-drier (BÜCHI B-290, Labortechnik AG, Switzerland) was used for the study. Lactose optical rotation was measured with a polarimeter, structural characteristic was carried out by X-ray diffractometer and glass transition analyses was made by TGA/DSC. α-Lactose monohydrate (Sigma-Aldrich, Germany) was used as a control. All spray-dried permeates samples showed amorphous state lactose crystals. The DSC analysis demonstrated a glass transition in the interval of 85–95 °C, melting 202–204 °C for spray-dried permeates lactose. In turn, the control sample showed crystallization at 158 ± 0.5 °C and a melting peak at 226 ± 0.5 °C. Optical rotation of spray-dried lactose obtained from sweet and acid whey permeate and milk permeate was in the range from 18 to 28°, control sample 52°. The study results showed that substrate, sample pH, ingredients and their derivatives impact lactose glass transition and mutarotation. The current study highlights the essential physical properties of spray-dried permeates lactose and the importance of its purity in food, cosmetic and pharmaceutical industry.