Physicochemical Properties, Sensory Acceptance and Storage Stability of Yogurt Flavored with Refractance Window Dried Passion Fruit Powder

Aims: The study evaluated the use of refractance window dried passion fruit powder as a flavoring for yogurt.

Place and Duration of Study: Department of Food Technology and Nutrition, Makerere University, Kampala-Uganda between October 2020 and January 2021.

Methodology: Passion fruit pulp was mixed in carboxymethyl cellulose and dried using a laboratory refractance window drier.

Plain yogurt was flavored with 2% passion fruit powder. Passion fruit flavored, plain and commercial yogurt were analyzed for physico-chemical and sensory properties. Statistical analyses were performed using XLSTAT and all results were considered to be significant at P<0.05.

Results: pH values and titratable acidity for all yogurts ranged from 4.67 to 3.77 and 1.21% to 2.89%, respectively throughout the 14 day storage period. The apparent viscosity of all yogurts increased significantly during storage and ranged from 413.76 cP to 525.20 cP, the syneresis of yogurts ranged from 25.6% to 32.2%, vitamin C content of the yogurts ranged from 0.69 mg/100 g to 1.91 mg/100 g, the carotenoid content of yogurts ranged from 0.55 µgRAE to 1.07 µgRAE, phenolic content of the yogurts ranged from 0.50 mg/100 g GAE to 8.01 mg/100 g GAE, whereas total antioxidant activity of the yogurts ranged from 0.21mg/100g VCE to 9.96mg/100g VCE. For all yogurt types, there was no significant change (p<0.05) in any of the sensory parameters (flavor, color, mouth feel, consistency, taste and overall acceptability) over the storage period of 14 days.

Conclusion: Addition of passion fruit powder to yogurt resulted in increased levels of vitamin C, beta carotenoid, total phenolic content and total antioxidant activity, in comparison to plain yoghurt and commercial vanilla flavored yogurt. This will provide consumers with more nutritious options thereby improving nutrition of consumers.