Quality, Shelf-life, and Consumer Acceptability of Probiotic Yogurt Enriched with Banana and Mango Fruit Peels

Abstract

This study evaluated the effects of incorporation of fresh mango peel (FMP) and fresh banana peel (FBP) on the physicochemical, microbiological, probiotic, and sensory characteristics of yogurt during 28 days of refrigerated storage. Proximate analysis showed that banana peel contained significantly higher dietary fiber (3.94 ± 0.74%) and carbohydrates (12.99 ± 0.26%) than mango peel (2.44 ± 0.11% and 10.62 ± 0.23%, respectively; p < 0.05), while mango peel had greater protein (2.86 ± 0.21%) and ash (3.76 ± 0.16%) contents. All yogurt samples experienced a pH decline over time, with more pronounced acidification in yogurts fortified with 10% FMP (pH 4.27 ± 0.01) and 10% FBP (pH 4.34 ± 0.01) by Day 28, compared to the control (pH 4.42 ± 0.01), indicating enhanced post-fermentation activity. Syneresis was significantly reduced by peel addition; on Day 28, control yogurt showed 45.00 ± 4.00% syneresis, while 10% FMP and 10% FBP treatments lowered this to 8.00 ± 0.00% and 12.00 ± 1.00%, respectively (p < 0.05). This reduction is attributed to the high dietary fiber in the peels, which improves water-holding capacity and gel stability in yogurt. Probiotic viability was notably improved in banana peel-fortified yogurts. Control and low-level FMP (1%, 5%, 10%) and 1% FBP samples had initial probiotic counts around 2.2–2.3 log10 CFU/ml ×106, decreasing to ~1.6–1.7 log10 CFU/ml ×106 by Day 28. In contrast, 5% and 10% FBP yogurts exhibited higher initial counts of 5.0 and 5.2 log10 CFU/ml ×106, respectively, maintaining levels above 3.0 log10 CFU/ml ×106 through Day 28. This enhancement is attributed to the fermentable oligosaccharides and prebiotic compounds present in banana peel, which promote probiotic growth and stability. Microbiological safety was confirmed, with yeast and mold counts remaining below Sri Lanka standards institute limits (<1000 CFU/g). Sensory analysis indicated that 10% FBP-fortified yogurts matched the control in acceptability, whereas higher mango peel levels reduced consumer preference. These results demonstrate the potential of fruit peel fortification as a sustainable strategy to improve yogurt quality, probiotic viability, and shelf life.