Blackberry production is increasing worldwide to meet a growing demand from consumers, especially in the fresh market (Clark and Finn, 2014). Unfortunately, maintaining fruit-eating quality from harvest to table is a main challenge for the fresh-market blackberry industry (Salgado and Clark, 2016; Segantini et al., 2017), and consumer appeal is greatly influenced by the deterioration of fruit following harvest (Clark and Finn, 2008). To counteract these difficulties, extensive breeding efforts have resulted in enhanced flavors and quality attributes, including recent crispy genotypes with improved postharvest performance (Salgado and Clark, 2016). Harvest and handling practices have also improved, as they ultimately affect postharvest quality and shelf life (Clark and Finn, 2008). For instance, many growers harvest early in the morning to minimize field heat and reduce the time before fruit is placed in cold storage.
Some of the most common and potentially devaluing defects in blackberry fruit are fresh weight (FW) loss, red drupelet reversion, and leakiness. Fresh weight loss occurs quickly since blackberries have high transpiration rates (Joo et al., 2011). These rates are often moderated by immediate cold storage but growers in many regions do not have in-field cold storage units, and both the time of harvest as well as amount of time from harvest to cold storage can affect final FW and postharvest quality. Red drupelet reversion, or reddening, is a common postharvest disorder by which drupelets revert from fully black to a bright red color (McCoy et al., 2016; Perkins-Veazie et al., 1996). Reversion is frequently observed following sudden temperature change after physical damage during harvest and shipping, or when exposed to room temperature after being in cold storage (Edgley, 2017; McCoy et al., 2016; Pérez-Pérez et al., 2018). Color reversion is theorized to be the result of internal cell structures rupturing and changing internal pH, leading to the degradation or lack of formation of anthocyanin pigments (Edgley, 2017; Pérez-Pérez et al., 2018). Reddening has also been reported to increase if blackberries are harvested later in the day as temperature increases (McCoy et al., 2016). Finally, visible leakiness of fruit also limits marketability and can reduce fresh-market price. Both harvest and postharvest conditions are important as leakiness can be increased by high temperature and high ultraviolet index at harvest and by the storage duration (Liu, 2014; Perkins-Veazie et al., 1999).
Since many cultivars ripen simultaneously during the growing season and growers often pick large quantities of fruit before transferring to cold storage, understanding of the effect of management practices on fruit quality of specific cultivars is needed. Growers could prioritize the harvest of cultivars based on time of day, develop harvesting plans based upon the need for prompt cold storage, and improve marketing strategies depending on cold storage duration without affecting fruit quality.
The objectives of this study were to understand and identify best practices for harvesting and storing fruit from 10 of the most commonly planted thornless blackberry cultivars. We hypothesized that fruit from some cultivars would be more predisposed to reduced fruit quality than others if harvested later in the morning, if transfer to cooling was delayed, or if storage time was extended.
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