Graduate Thesis Or Dissertation

 

Differential storage temperature and duration effects on ethylene synthesis and firmness of 'Anjou' pears Public Deposited

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  • 'Anjou' pears were sprayed with 2 concentrations of CaCl₂ during fruit development and harvested at 70 N flesh firmness. Pears were held at -1.1°, 5°, 10°, or 20°C for up to 100 days then ripened at 20°C for 11 days. Unexpectently, fruits stored at 20°C lost firmness and chlorophyll after 20 days without ethylene exceeding 0.3 ul/1. Only after 70 days did ethylene begin to rise above 1 ul/1 and be sustainable. Fruits stored at -1.1°C produced climacteric ethylene after 55 days and firmness decreased in response to climacteric ethylene. Fruits stored at 5° or 10°C required only 40 days to produce climacteric ethylene. Calcium-treated pears had significantly lower internal ethylene and greater firmness in all treatments, but calcium had only a small effect on ripening parameters of 10°C stored fruits. Both linoleic acid, the major fatty acid of 'Anjou' pear total lipids, and linolenic acid increased 100% during storage at -1.1°, and about 50% during storage at 5° or 10°C but did not increase during 20°C storage. Calcium treatments did not affect on fatty acid profiles. While linoleic acid simultaneously increased with chilling satisfaction, the significance of this relationship is not yet known. Fruits held at -1.1°C retained firmness and chlorophyll with little change in total proteins, amino acids, or soluble polyuronides. However, when fruit chilling requirements were satisfied (ie, after 70 days), internal ethylene peaked to 1.8 ul/1, ACC to 0.9 nmoles/g, and ethylene-forming enzyme(s) (EFE) activity to 71 nl C₂H₄/g/h, while titratable acidity decreased and sensitivity to propylene maximized. Pears stored at 20°C first softened, lost chlorophyll and titratable acidity and 15% of the cell wall polyuronides became soluble. Ethylene-forming enzyme(s) activity peaked then before ethylene, ACC, and total proteins increased. Sensitivity to propylene accelerated after the firmness decreased.
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Déclaration de droits
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