Nutritional value of peel and flesh of muscadine genotypes: a comparative study on bioactive compounds, total antioxidant activity, and chemical attributes

Muscadines ( Muscadinia rotundifolia Michx) have a thick peel that is often discarded by consumers. To better understand the potential nutritional loss due to this practice, total anthocyanin concentration (TAC), total phenolic content (TPC), total antioxidant activity (TAA), and chemical attributes in peel and flesh of eight purple muscadine genotypes were evaluated to determine the nutritional value of each part. Muscadine genotypes that were used in this study included two commercial cultivars (‘Supreme’ and ‘Paulk’) and six selections (‘Ga.10-1-222’, ‘Ga.10-1-294’, ‘Ga.10-1-329’, ‘Ga.12-5-46’, ‘Ga.12-3-22’, ‘Ga.13-4-79’). Bioactive compounds, antioxidant activity, and titratable acidity (TA) were higher in the peel of all muscadine genotypes, while the flesh had more sucrose, glucose, and fructose. In the peel, TAC (20.68–37.53 mg L − 1 ), TPC (382.84-577.31 mg GAE L − 1 ), ellagic acid (5.44–15.5 µg mL − 1 ), TAA (436.07-1258.26 µmoles TE L − 1 ), total soluble solids (TSS, 11.45–16.62%), TA (0.64–1.17%), TSS/TA ratio (10.92–24.46), pH (3.42–3.82), sucrose (13.73–69.49 mg mL − 1 ), glucose (58.42–77.69 mg mL − 1 ), and fructose (19.26–26.84 mg mL − 1 ) varied significantly among different cultivars. Similarly, in the flesh, the ranges of TAC (0.38–2.33 mg L − 1 ), TPC (11.48–26.52 mg GAE L − 1 ), ellagic acid (0.02–0.3 µg mL − 1 ), TAA (14.65–21.62 µmoles TE L − 1 ), TSS (12.25–17.3%), TA (0.43–0.73%), TSS/TA ratio (19.44–35.34), and pH (3.44–3.73), sucrose (39.33-124.02 mg mL − 1 ), glucose (71.75–92.86 mg mL − 1 ), and fructose (24.25–32.25 mg mL − 1 ) were significantly different among different cultivars. The ‘Supreme’ peel exhibited the highest TAC, TPC, and TAA, while the peel of ‘Ga.12-3-22’ had the lowest values. In ‘Supreme’ fruit, the TAC values ranged from 0.382 mg L − 1 in the flesh to 37.53 mg L − 1 in the peel. The TPC values showed variability between 17 and 577 mg GAE L − 1 in both flesh and peel. Furthermore, TAA values ranged from 1258 to 16 µmoles TE L − 1 in both peel and flesh. The peel contained over 90% of the ellagic acid in the fruit, with ‘Ga.12-5-46’ peel having the highest ellagic acid overall. The ellagic acid content in the peel of ‘Ga.12-5-46’ was 15.5 µg mL − 1 , which was 144 times greater than that in its flesh. ‘Ga.13-4-79’ had the highest TA in both peel and flesh. The highest sucrose content in both peel and flesh occurred in ‘Ga.10-1-329’ and ‘Ga.12-3-22’, while ‘Ga.12-5-46’ and ‘Ga.13-4-79’ had comparatively lower sucrose in flesh. Given the substantial phytochemical content present in muscadine peel, discarding the peel constitutes a missed opportunity of considerable magnitude to obtain the full nutritional benefits of muscadines.