The Effects of Fermentation Time and the Addition of Blueberry on the Texture Properties and In Vitro Digestion of Whey Protein Gel

The interaction of blueberry and whey protein has strong antioxidant properties and potential antibacterial and anti-aging functions during the fermentation process. In this study, the properties of fermented gels derived from whey protein mixed with blueberry juice were investigated for the production of probiotic-rich products such as jelly and pudding. The microstructure, water-holding capacity, texture changes, rheological properties, and digestive characteristics of fermented gels were evaluated in vitro. The fermented gels with a mixture of whey protein and blueberry exhibited a honeycomb structure, observed by SEM. The adhesiveness of the gel with a mixture of blueberry and whey protein was the highest at 7.5 h and 8.0 h, respectively. The storage modulus (G′) and loss modulus (G″) of the mixed gels were higher than those of whey protein gels before 6 h of fermentation. When the fermentation time was 8 h, the release of polyphenols, flavonoids, and proteins was fastest and greatest during the digestion of gastric and intestinal fluid ether for the whey protein fermented gel and the mixed fermented gel. The water-holding capacity of the mixed gels was lower than that of the whey protein fermented gels during the fermentation period of 8 h. The viable counts of the mixed fermented gels could reach 10⁷ CFU/mL, which was higher than those of whey protein gels after 6 days of storage.