Changes in Water Soluble Polyuronides in the Pulp Tissue of Ripening ‘Bosc’ Pears following Cold Storage in Air or in 1% Oxygen

Abstract

Abstract ‘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.