From Harvest To Consumer: Are Grape’s Health-Beneficial Properties Modified With Time In Storage?

Abstract

Abstract Objectives Currently, the intake of fruits and vegetables is lower than the recommended amounts, despite the known association between consumption of plant foods and prevention of several chronic diseases. Grapes are a widely accepted and consumed fruit, and one of the richest in phytochemicals that are beneficial to human health. Previously, we reported that growing cold hardy table grapes on two different grapevine training systems, Modified Munson (MM) and Vertical Shoot Positioning (VSP), modulates their amount of total phenolics and antioxidant potential at harvest. However, consumers access to fruit is usually not immediate upon harvest, but could take weeks/months before reaching stores. The objective of this study was to evaluate whether phenolics and antioxidant potential of table grapes grown on different training systems could be maintained post-harvest in cold storage. Methods Cold-hardy table grapes variety Mars were grown on two grapevine training systems, MM and VSP. At harvest, randomly picked grape clusters from each training system were placed in clamshells (2 clusters per clamshell) and placed in cold storage (0 ± 1°C). After 1, 2 and 3 weeks post-harvest, grapes (triplicate clamshells) were homogenized and Brix, titratable acidity, antioxidant potential and total phenolics were analyzed. Statistical analysis was performed using 2-way ANOVA. Results Total phenolics were greater for MM compared with VSP (MM 2.56 vs. VSP 1.84 mM Catechin equivalents; P = 0.0001), but were reduced in cold storage irrespective of training system (P = 0.0002). The MM training system had greater Brix (MM 17.9 vs. VSP 15.8°Bx; P < 0.0001) and antioxidant potential (MM 1.24 vs. VSP 1.01 mM Fe2+ Equivalents; P = 0.0379) than VSP system. The results also showed an effect of training system x time interaction (P = 0.0371) on titratable acidity. Conclusions Our data suggest that greater total phenolics, antioxidant potential and Brix associated with the MM compared with VSP training system are maintained in the post-harvest period. Our data also suggest that nutritional properties of grapes is reduced post-harvest, despite being in cold storage. Thus, grapevine training system and cold-storage play a role in producing grapes with increased health-beneficial properties. Funding Sources USDA NIFA Hatch.