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The application of processing waste by-products along with probiotics is an interesting choice to confer potential functional aspects to food products. This study was designed to investigate the nutritional capacity of freeze-dried mango peel powder (MPP) and banana peel powder (BPP) in the presence of a mixture of three probiotic species (1% of each of three probiotics (Lacticaseibacillus casei (431®), Lacticaseibacillus rhamnosus (LGG®) and Bifidobacterium subsp. Lactis (Bb-12®)) as sources of additional nutrients and prebiotics in fresh and rehydrated freeze-dried (RFD) yogurts for 28 days of refrigerated storage. The net count of probiotics in yogurt fortified with MPP and BPP increased by at least 1 log CFU/g after 4 weeks of refrigerated storage. Adding fruit peel powder (FPP) significantly (p < 0.05) increased fat, ash, and protein contents in both fresh and RFD yogurts in comparison with the control yogurt. Similarly, the total phenolic contents (TPC) and antioxidant activity (AOA) was enhanced significantly (p < 0.05). The TPC reached 2.27 ± 0.18 and 2.73 ± 0.11 mg GAE/g in RFD enriched with BPP and MPP compared to a TPC of 0.31 ± 0.07 mg GAE/g in the control. Additionally, yogurt samples enriched with BPP (Y-5) and MPP (Y-6) demonstrated 12% more sugar contents than non-fortified yogurts (Y-1). Higher titratable acidity and lower pH values were also recorded in the RFD yogurt. Significant differences (p < 0.05) in the color parameters were detected in both fresh and RFD yogurts with reduced brightness (L*) and increased redness (a*) of the product. These findings demonstrated the suitability of MPP and BPP in yogurt formulations to optimize the advantages of such synbiotic products with higher availability of phenolic compounds.
Zahid et al. (Mon,) studied this question.