| Abstract [eng] |
The final master’s project is designed to investigate the application of lactic acid bacteria, enzymes and phenolic compounds to the modification of whey protein products. In this work, the hydrolysis of whey proteins using enzymes (pepsin P7000, protease from Bacillus amyloliquefaciens P1236 and pancreatin P1750) was performed. The influence of temperature, pH and hydrolysis time on the efficiency of whey protein hydrolysis, antioxidant and antimicrobial activity of whey protein products were investigated. The highest efficiency of hydrolysis (1.98 µmol/ml released tyrosine) was obtained using pepsin for 40 min at 50 oC and pH 3. The highest antioxidant and antimicrobial activity were observed in the samples of whey proteins treated with pepsin for 40 minutes at 40 oC and pH 3. The highest hydrolysis efficiency of whey proteins treated with pancreatin and protease was obtained by hydrolysis 40 minutes at 40 oC and pH 7.5. Whey fermentation was performed using lactic acid bacteria (Lactobacillus plantarum DSM 20174, Lactobacillus acidophilus DSM 20079 and Bifdobacterium bifidum DSM 20082). Total protein content in whey decreased during enzymatic hydrolysis. The whey protein sample fermented for 32 hours with Bif. bifidum showed the highest protease activity (11 AV/ml). The study shows that the antioxidant properties of whey protein products increase with increasing fermentation time. The antimicrobial properties of fermented whey products were enhanced by prolonged fermentation. The tested samples of whey protein products were antimicrobially active against pathogenic bacteria (Staphylococcus. aureus, Bacillus cereus, Escherichia coli ir Salmonella typhimurium). The sodium dodecylsulphate polyacrylamide gel electrophoresis showed the changes of whey proteins after fermentation and enzymatic hydrolysis. Modification possibilities of whey proteins with various phenolic compounds (gallic acid, carvacrol and m-cymene) have also been identified. The study showed that the antioxidant properties were improved by modifying the whey proteins with phenolic compounds (up to 12 times on average) and the antimicrobial properties – up to 2 times. |
