Thermal capacity of pear fruit of winter varieties for storage
Keywords:
storage ability, pear fruit, the rate of cooling and heating, physical and thermal pear fruit indicators, temperature, dynamic difference, refrigerator, fruit weight, heat capacityAbstract
Background. Fruits are open biological systems in which natural processes continue even after picking up the fruit from the tree. We can slow them only by biological stabilization, which requires the creation of appropriate physical storage conditions. Purpose of the study is to determine the speed of the process of lowering the temperature to the optimum for winter varieties of pears when laying them for storage.
Material and methods. Pear fruit of winter varieties Zolotovorotska, Etiud, Cure, Concord, Yuzhanka was studied. The dynamics of temperature and enthalpy [6] during cooling the fruit to the optimum storage temperature in refrigerated chambers and during warming was conducted in accordance with the "Guidelines for the storage of fruits, vegetables and grapes" [7]. Changes in temperature at the center of the fruit were measured by thermosteam.
Results. The longest time (11 h) for a decrease in temperature to the optimum required Cure sort that had the greatest weight and size of the fruit. The quickest of all (5.5 h) was cooled pear variety Yuzhanka. At about the same sort of physical parameters of Eitud difference in the duration of cooling was 1.5 ° C for Yuzhanka, in which the rate of temperature decrease in the relative percentages was significantly higher than for Etiud (Table 2).
Progress in reducing the temperature in the center of the fruit is differnt: it is intense in the first hour of cooling, and then it starts to slow down. In some periods of the process there are significant jumps in the intensity of lowering the temperature of the fruit.
Heating rate of fruit was quicker than cooling (Table 4). With placing the fruit in a warm room after 30 minutes there was a sharp rise in temperature and heat content in all varieties. In the next 2–2.5 hours the intensity of these processes gradually decreased, and after heating to 12–13 ° C increase in temperature to its initial level was slow.
Conclusion. Rate of physical and thermal processes during cooling pear fruit of winter varieties depends not only on the ambient temperature, but also on genetic characteristics of the variety.
Dynamics of decrease and increase of temperature of pear fruit is uneven at the same time that should be considered when monitoring the temperature conditions during storage in refrigerator.
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