Abstract:
'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.
