Evolution of Physico-chemical Indices and Functional Properties of Fruit Yogurt during Storage

Abstract

Background: In the context of the current trend of consumers to consume foods as natural as possible, increasing the nutritional and biological value of yogurt by using raw materials (goat's milk and fruit) with a well-balanced chemical composition is of great interest in the dairy products manufacture.

General Objective: The study and analysis of fruit nutritional and biological value impact on quality indices and funtional properties of goat's milk and cow's milk yogurt during the storage.

Methods: The yogurt was obtained from a mixture of 50% goat's milk and 50% cow's milk with the addition of aronia (Aronia melanocarpa), raspberries (Rubus idaeus), strawberry (Fragaria xanassa) fruits. Physico-chemical indices and biological value were determined according to standard methods in 1, 5, 10, 15 days of storage.

Results: Sample's titratable acidity shows increasing values, being influenced by the addition of fruits, that have a higher acidity compared to classic yogurt but remaining in the range of allowable values. The pH of the yogurt samples decreases with increasing storage period, as the metabolic activity of the starter culture persists. Yogurt with added aronia (P2) has the best values of total dry matter (18.45 ± 0.31%), water activity (0.875 ± 0.025), viscosity (2500 ± 0.023 mPa·s) and the highest content of anthocyanins of 66.03 mg/100g, the highest polyphenol content of 268.97 mg GAE · 100g-1 and the best values of antioxidant property of 2.2 ± 0.025 mg AA/g SH. Strawberry yogurt (P4) has the highest content of vitamin C (47.87 mg/100g) and carotenoids 0.292 mg/100g.

Conclusion: Fruit addition had a positive impact on the quality indices of yogurt during storage.