Physicochemical and Sensory Evaluation of Low-Fat Yogurt Treated with Alfalfa Seed Powder

Recently, alfalfa (Medicago sativa) has been used to improve the nutritional quality of food products, including gluten-free cookies and biscuits. In the present study, the effects of the addition of alfalfa seed powder on the physicochemical, sensory, and antioxidant properties of low-fat yogurt (1.5%) were investigated. Different concentrations of alfalfa seed powder (Y0, control; Y1, 0.25%; Y2, 0.5%; Y3, 0.75%) were used to prepare yogurt samples, which were stored for 14 days at 4°C. Following enrichment, the acidity and viscosity of the samples increased. However, the pH and syneresis significantly decreased over time with increasing alfalfa seed powder concentrations (P<0.05). The inclusion of alfalfa significantly enhanced the antioxidant properties of samples. On the first day, Y3 showed the highest total phenolic content (27.35±0.25 mg GAE/g), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (51.76%±0.68%), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) activity (83.65%±0.27%) among all samples (P<0.05). The addition of alfalfa seed powder also significantly improved the yogurt's lipid profile by increasing the levels of α-linolenic acid (6.19%±0.61% in Y3 vs. 0.55%±0.08% in Y0) and linoleic acid (5.88%±0.43% in Y3 vs. 3.59%±0.17% in Y0) and decreasing the levels of saturated fatty acids (P<0.05). During storage, the color parameters of Y3, including lightness and whiteness, significantly decreased, but its yellowness increased compared with that of Y0 (P<0.05). However, the sensory properties did not significantly change in any of the yogurt samples. These results suggest that the addition of alfalfa seed powder enhances the functional and nutritional value of yogurt, and it can be considered as a potential functional food ingredient.