Nutritional Composition and Health-Promoting Properties of Amasi: A South African Fermented Milk Product

This study investigated the effect of fermentation conditions (time and temperature) on the nutritional composition and health-promoting properties of raw milk, optimized naturally fermented amasi, and amasi fermented with starter culture. The composition of the products, including chemical analysis, amino acids, mineral composition, and fatty acids, as well as health-promoting properties (total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity assays (2,2-Azinobis (3-Ethyl-Benzothiazone-6-Sulphonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) were investigated. The results showed that the fermentation conditions (time and temperature) significantly affected the ash contents of both fermented samples. Fermentation was also observed to have increased the contents of most of the essential and non-essential amino acids. A high concentration of glutamic acid was observed in optimized naturally fermented amasi at 32 °C (OP32, 6.30 g/100 g), followed by starter-culture-fermented amasi at 25 °C (SC25, 5.58 g/100 g) and then starter-culture-fermented amasi at 32 °C (SC32, 5.35 g/100 g), with optimized naturally fermented amasi at 32 °C (OP25, 4.46 g/100 g) having the lowest concentration. A similar trend in the composition of minerals was also observed, with potassium being the most abundant (110.1–134.5 µg/g). The TPC, TFC, and the antioxidant activities were significantly improved by fermentation, while a significant reduction in free fatty acids was recorded. In conclusion, the fermentation conditions had a significant effect on the nutritional and health-promoting properties of amasi. The results provided in this study could provide nutritional information regarding the composition of amasi, which can be beneficial to produce a high-quality product.