No abstract

Ethylene production of ‘Bartlett’ pears (Pyrus communis L.) was suppressed by 1 % O2 during storage at − 1°C. Elevated CO2 concentrations further suppressed ethylene production. Organic acids were retained at higher levels in fruits stored in 1% O2 than in those stored in air, and elevated CO2 concentrations in 1% O2-enhanced acid retention. Both malic and citric acids decreased linearly during 8 days of ripening at 20° regardless of previous storage conditions. The suppression of ethylene production and the retention of organic acids implied a beneficial effect of elevated CO2 in storage of ‘Bartlett’ pears at 1% O2. Fruit stored in 1% O2 at −1° for 4 months developed brown-core regardless of CO2 levels in the storage, but the incidence of the disorder was enhanced when CO2 level in the storage was ≥2%. This preliminary study indicated that ‘Bartlett’ pears grown in the Hood River district of Oregon could be stored at −1° for 4 months in 1% O2 with CO2 at <1.5% with a minimum risk of brown-core development.

‘Bosc’ pears (Pyrus communis L.) harvested at an optimum maturity, based on flesh firmness (about 62 N), were stored either in air or 1% O2 (plus <0.03% CO2) at −1°C. Fruit stored in air for 1 to 3 months softened rapidly after 2 days of ripening at 20°C and reached ripeness with flesh firmness of 20 N or lower by the 9th day. Ripening was associated with a reduction in extractable juice (EJ) and an apparent increase in water soluble polyuronides (WSP). Fruit stored in air for 4 to 5 months also softened rapidly after 2 days of ripening, but flesh firmness was still between 26 and 30 N after 9 days; however, EJ and WSP of fruit did not change appreciably during 9 days of ripening. The WSP content in fruit stored in either air or 1 % O2 increased substantially during 6 months of storage at −1°C. Increased WSP content during storage did not affect the quantity of EJ. Fruit stored at 1% O2 showed a reduction in EJ and an increase in WSP during the 9-day ripening period, whereas, in long-term air-stored fruit, EJ did not decline while WSP was degraded. Correlation of EJ and WSP during each ripening period provided an estimation of storage life. Increased WSP after ripening might be responsible for the increase in hygroscopic binding capacity of the ripened pulp tissue.

‘Bose’ pear fruits (Pyrus communis L.) grown in northern Oregon (NO, Hood River) and southern Oregon (SO, Medford) were harvested during the commercial harvest period and stored in either 1 % O2 with trace CO2 or in 5 other controlled atmosphere (CA) regimes, O2/CO2 at 0.5%/0%, 1.0%/0.5%, 1.5%/0.5%, 2.0/0.5%, and 2.5%/1.0%, for 6 months at −1°C in 1982, 1983, and 1984. Fruits from the NO were more susceptible to brown core (BC) disorder than those from SO. Late-harvested fruits, especially from NO, were more susceptible than early harvested ones. A low O2 concentration of <1% in CA storage without CO2 increased the potential for fruit to develop BC, and an elevated CO2 level enhanced the effect of low O2. Based on this study, it is recommended that ‘Bose’ pear fruits from NO can be safely stored in O2 not less than 1.5% with trace CO2 and those from SO in O2 as low as 1% with CO2 between 0 and 0.5% for 6 months at −1° with little probability of BC.

‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) were passed through several brushrollers during washing, rinsing, waxing, and drying sequences of a simulated packing process. In-line application of Fresh-Cote, a wax coating formula with porosity, to the pear surface at waxing location of the packing line reduced peel discoloration of ‘Bartlett’, but not ‘d’Anjou’, due to brush friction. Fruits also were subjected to a return flow belt for 5 minutes to simulate the sorting sequence during packing. Fresh-Cote substantially reduced the susceptibility of both ‘Bartlett’ and ‘d’Anjou’ pears to peel discoloration due to belt friction.