Physicochemical and Rheological Characteristics of Stirred Yogurt Fortified with Vitamin B12 and Melatonin

Abstract

Vitamin B12 and melatonin were added to whole milk-stirred yogurt to evaluate its physicochemical (fat, protein, total solids, moisture, syneresis, and color), rheological (flow behavior and dynamic rheology), and color characteristics as L , a ∗ , and b ∗ and color change ( ∆ E ). For this, five treatments (T) were elaborated as follows: T1 = yogurt (Y) without vitamin B12 and melatonin, T2 = Y with 3 μg/L of B12, T3 = Y with 5 mg/L of melatonin, T4 = Y with 2 μg/L of B12 and 3 mg/L of melatonin, and T5 = Y with 3 μg/L of B12 and 5 mg/L of melatonin. The fortification of yogurt with vitamin B12 and melatonin modified ( P < 0.05 ) the content of fat, moisture, and syneresis. Treatment 5 presented the lowest content of fat and the largest content of moisture ( P < 0.05 ). Treatment 4 had the largest syneresis at day 1, and at day 14, there was not differences in syneresis among treatments ( P > 0.05 ). Regarding color, luminosity ( L ∗ ) did not have significant differences ( P > 0.05 ) among treatments and neither among storage days, except for T5 that presented the lowest value at day 14. Regarding parameter a ∗ , all treatments presented negative values (tendency to green), and T2, T3, and T5 showed significant differences ( P < 0.05 ) trough time. No significant differences ( P > 0.05 ) were observed for the b ∗ values neither among treatments nor among time. The highest value in Δ E , compare to the control, was observed in T5. Regarding flow behavior, T1 showed a significantly different ( P < 0.05 ) higher flow behavior ( n ) than the rest of the treatments. In general, all the samples indicate an increase ( P < 0.05 ) in the flow behavior ( n ) through the storage time. And the consistency index ( K ) showed significant difference ( P < 0.05 ) between T1 and T2 and T3 and T4. In conclusion, the addition of vitamin B12 and melatonin to yogurt generates changes in the physicochemical and rheological properties; likewise, the addition of melatonin in combination with vitamin B12 showed that the viscoelastic characteristics of the fortified yogurts are like the control yogurt. Since these, treatment 5 presented the most similar values of rheology and syneresis compared to the control, so this combination of B12 and melatonin could be employed to develop a new functional yogurt.