Impact of muscadine genotype on postharvest fruit quality and storability

Abstract

The postharvest changes in bioactive compounds and antioxidant activity of the whole fruit, peel, and flesh, as well as color, weight and firmness changes, were investigated in six commercial muscadine cultivars (three purple: ‘Alachua’ (AL), ‘Paulk’ (PA), and ‘Supreme’ (SU); and three bronze: ‘Granny Val’ (GV), ‘Hall’ (HA), and ‘Triumph’ (TR) during cold storage at 4 °C for 42 days. Weight loss increased significantly (P < 0.05), with SU losing 5.79% and HA losing 8.23% by day 42. Firmness significantly (P < 0.05) decreased during cold storage, with SU displaying the higest (164.02 g mm−1) and HA the lowest (110.75 g mm−1) by the end of storage. Total soluble solids (TSS), titratable acidity (TA), and their ratio (TSS/TA) showed variations among cultivars and parts of the fruit, with purple cultivars consistently exhibiting higher titratable acidity (TA) compared to bronze cultivars, while bronze cultivars demonstrated higher TSS/TA ratios. TSS ranged from 13.25 to 16.8%, TA from 0.62 to 0.84%, and TSS/TA ratios varied from 20.53 to 41.23 across cultivars (in whole fruit). HA (15.32%) and TR (15.32%) exhibited the highest TSS content, while GV had the lowest TSS at 13.25%. In terms of TA, AL had the highest value at 0.86%, whereas HA (0.46%) and TR (0.51%) recorded the lowest TA. The TSS/TA ratio ranged from 18.31 in AL to 36.85 in HA, representing the lowest and highest ratios, respectively. Color parameters differed between purple and bronze cultivars, with purple cultivars displaying higher a* (red component), while bronze cultivars had higher L* and C* values (lighter and more pure color); the h° values of the purple and bronze cultivars were also significantly (P < 0.05) different, but did not differ within each group. The purple cultivars had higher total anthocyanin concentration (TAC) (8.4–15.31 mg L−1), total phenolic content (TPC) (92.11–107.01 mg GAE L−1), and total antioxidant activity (TAA) (150.25–250.05 μmoles L−1) than the bronze cultivars, and the peel had higher levels of those bioactive compounds than the flesh. AL exhibited the highest TAC at 15.31 mg L−1, followed by SU (13.01 mg L−1) and PA (8.4 mg L−1). In terms of TPC, AL (107.01 mg GAE L−1) and SU (92.11 mg GAE L−1) had the highest levels, with PA (74.89 mg GAE L−1) following. Among the bronze cultivars, TR had the highest TPC (61.41 mg GAE L−1), while GV exhibited the lowest (35.09 mg GAE L−1). The TAA of the purple cultivars ranged from around 250 to 134 μmoles L−1 TE in whole fruit, 500 to 319 μmoles L−1 in the peel, and 17 to 10 μmoles L−1 in flesh, while the TAA of the bronze cultivars ranged from about 122 to 56 μmoles L−1 TE in whole fruit, 248 to 120 μmoles L−1 in the peel, and 16 to 10 μmoles L−1in the flesh. During cold storage, TAC, TPC, and TAA decreased in both the peel and the flesh, but more so in the peel. Two of the three purple cultivars (SU and AL) maintained more TAC, TPC, and TAA in the peel than the three bronze cultivars. Based on our results, the purple muscadine cultivar SU, followed by purple PA and AL, exhibited better storability than the bronze cultivars in terms of maintaining their quality factors closest to the initial values. Among the bronze cultivars, GV exhibited the best storability. Overall, the order of storability of muscadine cultivars was SU, PA, AL, GV, TR, and HA.