Characterizing the Effect of Harvest Maturity on Ripening Capacity, Postharvest Fruit Quality, and Storage Life of ‘Gem’ Pear

Abstract

‘Gem’ is a recently-released, unique European pear cultivar that possesses crisp, juicy texture and exceptional eating quality at harvest, but can also ripen to a soft, buttery texture; however, relatively little is known about the optimal harvest maturity (HM) and storage behavior of the fruit. We, therefore, evaluated the effect of HM on postharvest fruit quality attributes of ‘Gem’ pears [fruit size, flesh pressure (FF), soluble solids concentration (SSC), titratable acidity (TA), and extractable juice (EJ)] in two different seasons. Four and two harvests were performed one week apart in 2011 and 2012, respectively. Fruit were stored in regular air (RA) for 7 months and evaluated monthly, either directly from cold storage (un-ripened), or after provision of a 7 day ripening regime (ripened). Throughout the 7 month storage period, un-ripened pears behaved fairly similarly despite a wide range in HM (i.e., FF between 54.3 to 42.7N). In general, FF decreased 0.5 to 0.75 N per month; TA declined by ~40%; and, EJ and SSC remained relatively stable. Fruit size, however, significantly increased with each delayed harvest date. Fruit required a minimum of 30 days cold storage to attain ripening capacity (i.e., to soften to ≤17.8 N and develop a buttery, juicy texture), though results differed depending on year and HM. Ripened fruit had significantly lower EJ than non-ripened fruit. After 5 months in RA storage, EJ and FF of ripened fruit increased in both years indicating the loss of ripening capacity. Internal browning was not observed until 6 or 7 months, depending on HM. Respiration and ethylene production rate (EPR) of ‘Gem’ pears, measured daily for 15 days (at 20°C), progressively increased between 1 and 5 months of RA storage. At 6 months, a change in the pattern of EPR signified the end of the eating-quality, storage life. For both ripened and un-ripened ‘Gem’ pears, optimal fruit quality was achieved at a HM between 44 and 42N. At a harvest pressure of 44 N, fruit showed no increase in scuffing incidence after processing over a commercial packing line. The maximum RA storage life of ‘Gem’ pears was 5 months.