Quantification of protein fractions in aqueous phases of whey and emulsions

Sammanfattning: Aqueous 6.86% whey protein concentrate 35 (WPC 35) solution was heated at the temperature of 70°C for 10, 15 and 20 minutes respectively to quantify the amount of native protein, soluble protein aggregates and insoluble protein aggregates in the heated samples. The serums of the emulsions formed from the different heated samples were also analyzed for percentages of native proteins and aggregated proteins using Dumas combustion method. The aim of this work was to improve the knowledge on the functionality of WPC 35 with a heat treatment of 70°C at varied period of time. The results show that there was native protein fraction of 76.6%, 14.4% soluble protein fraction and 9% insoluble protein aggregates when aqueous 6.86% WPC 35 solution was heated at 70°C for 10 minutes. Emulsion formed from the heated sample contains 78.2% native protein in its serum after centrifugation. With a heat treatment of the same sample at 70°C for 15 minutes, the content of native protein fraction was 73%, 8.3% soluble protein fraction and 18.7% insoluble protein aggregates. The resulting emulsion from this heat treatment had 66.9% native protein in its serum after centrifugation. Heat treatment of aqueous 6.86% WPC 35 at 70°C for 20 minutes contains 80.43% of native proteins, 5.6% of soluble protein and 13.97% insoluble proteins. The emulsion prepared from the heated sample has 81.7% native proteins in its serum. Effect of some other processing conditions such as homogenization and length of storage of whey protein dispersion were also examined.