Effect of acid whey protein concentrate on the rheological properties, antioxidant capacities, and biological activities of bioaccessible fractions in fermented camel milk

The production of set-type camel milk yogurt is challenging due to its unique physicochemical properties, which differ from those of other milk species. The present study aimed to evaluate the effects of camel milk supplementation with different levels (0% [WPCA0], 3% [WPCA3], and 6% [WPCA3]) of whey protein concentrate (WPC) on the texture, rheological properties, antioxidant capacity, and biological activity of camel milk yogurt compared with bovine milk (BM) yogurt. These characteristics were evaluated before and after in vitro digestion of yogurt samples after 1 and 15 d of storage at 4°C. The results show that using WPC, particularly at 6% (WPCA6), significantly affected the characteristics of yogurt. The water-holding capacity increased by increasing the level of WPC and showed higher values than BM yogurt. Furthermore, the adhesiveness in yogurt samples containing 6% of WPC was significantly higher than other treatments, representing 6.3 and 6.1 mJ after 1 and 15 d, respectively. The apparent viscosity of WPCA6 was also higher than other yogurt treatments at different shear rates throughout storage, indicating a thicker and more viscous yogurt. Camel milk yogurt showed higher 2,2-diphenyl-1-picrylhydrazyl values, representing 74.1%, 71.6%, and 78.1% for WPCA0, WPCA3, and WPCA6, respectively, compared with BM yogurt (22.9%). The biological activities, including α-amylase, α-glucosidase, and angiotensin-converting enzyme inhibition, increased after in vitro digestion of yogurt samples. Principal component analysis underscored the distinct bioactive profile of WPCA6, distinguishing it from other yogurt treatments and highlighting its superior properties.