Effects of Pulp Temperature at Physical Impact on Blueberry Fruit Quality

Abstract

Blueberries (Vaccinium spp.) destined for fresh market undergo numerous impacts during harvest and handling; pulp temperature also varies due to weather and grower handling practices. Southern highbush blueberry fruit (var. ‘Meadowlark’) were hand-harvested into plastic lugs at a commercial farm in north-central Florida and transported to the Postharvest Horticulture Laboratory in Gainesville. The objective of this study was to study the effect of fruit pulp temperature and time delay on susceptibility to physical impact. Sorted blueberries (n = 20) were placed into each of two clamshell containers for five temperatures and two delay periods. Fruit were held at (5, 10, 15, 20, or 30 °C) for 5 or 24 hours, then fruit were individually dropped once onto a solid surface from 60 cm or left undropped (control) and immediately evaluated for weight loss and firmness. Fruit were then frozen at –30 °C for later chemical analysis of soluble solids content (SSC) and total titratable acidity (TTA). Weight loss was higher in dropped fruit (0.11% to 0.35%) than in undropped fruit (0.03% to 0.26%) for all pulp temperatures and delay periods. Although there was little effect of pulp temperature on blueberry firmness, fruit dropped at 30 °C were 12% softer than undropped fruit. Holding fruit for 24 hours prior to dropping resulted in more softening compared to undropped fruit after 5 hours. The SSC averaged 14.3 and 14.2 °Brix for dropped and undropped fruit, respectively. Blueberry TTA values, reported as percent citric acid, were similar between dropped (0.25%) and undropped fruit (0.27%). These results indicate that even short exposures of blueberries to higher temperatures can promote increased weight loss and softening.