Physical and biochemical changes in pears during storage and ripening Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/pk02cd27x

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  • A study has been made of the interrelations between certain of the physical and biochemical changes in three varieties of pears during storage and ripening. The metabolic changes which occurred in the fruit during cold temperature storage were found to influence with development of certain characteristics associated with dessert quality of the ripened fruit. The nature of these changes varied according to variety. The rate and degree of softening at a temperature favorable for ripening (68-70°F.) varied considerably according to variety and according to length of the storage period. Bartlett pears decreased rapidly in pressure test when ripened in October and November. Bosc pears softened slower and to a lesser degree. Both varieties failed to soften and ripen normally after prolonged periods of storage. This condition was not observed in Anjou pears, but this variety ripened in April tended to have a mealy texture. The amounts of both protopectin and total pectin increased during storage in all the three varieties. Anjou pears contained more total and protopectin than the other two varieties. The data on pectin changes indicate a possibility of synthesis of protopectin during storage. A possible explanation for such phenomenon is discussed. There is a fairly significant correlation between per cent protopectin and pressure test. The percentage of extractable juice was inversely correlated with fruit firmness, and increased rapidly during ripening. Highest yields of extractable juice were obtained from Anjou and Bartlett pears, and the percentages decreased in all varieties with increase in length of storage period. Low extractable juice content was correlated with the loss of ripening capacity in Bartlett and Bosc pears and the occurrence of mealy texture in Anjou pears. The relative viscosity of the juice increased during the ripening process and was highest in all varieties after short periods of storage. Total acid content of all varieties varied to some extent but no consistent trends were observed. In all varieties total solids increased with ripening, and were lower in Bartlett and Bosc than in Anjou pears. The use of activated carbon treatment of the storage atmosphere retarded the rate of loss of green color. No effect on the metabolism of pectic substances was apparent in Bartlett and Bosc pears, while the data for Anjou pears were not consistent.
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