Abstract
The quality of horticultural products can be promoted using high techniques. One of these methods is precooling applied before storage and leads to increased shelf and storage life of the fruit. For this reason, the effect of forced air cooling was conducted to investigate the cooling rate at the center (aril), spongy tissue (peel) and leathery skin (rind) of pomegranate (Punica granatum L.). Airflow velocity as an effective factor in cooling products at three levels of 0.5, 1, and 1.3 m s-1 and temperature of 7.2 °C was considered. Cooling parameters including lag factor and cooling coefficient were calculated from experimental data. Then, half-cooling time and seven-eighths cooling time were obtained at different layers of pomegranate. Cooling heterogeneity was analyzed at different air velocity and at different layers of pomegranate. The results showed that increase in air velocity from 0.5 to 1.3 m s-1, reduced the half-cooling time and seven-eighths cooling time. After 5000 seconds, the change of air velocity had a slight influence on decreasing temperature of different layers of pomegranate. Cooling heterogeneity at the air velocity of 0.5 m s-1 was low and then increased at the air velocity of 1 m s-1. Finally, at the air velocity of 1.3 m s-1, it was declined. The overall results illustrate that the applied methodology in this research, which explains unsteady heat transfer in the cooling process, can be performed in pomegranate or similarly shaped fruits.
Highlights
Pomegranate (Punica granatum L.) is a plant from the family of Punicaceae (Fadavi et al 2006) and Iran is the main origin of planting this fruit
Given the above considerations, cooling methods can be divided into the following methods: forced air cooling, room cooling, vacuum cooling, hydrocooling, evaporative cooling, and ice cooling (Brosnan & Sun 2001)
The objective of the present study was to evaluate the velocity of cold air as an effective factor in the rate of cooling, estimate cooling parameters, and precise determination of cooling time at the different layers of a pomegranate, namely Rabab
Summary
Pomegranate (Punica granatum L.) is a plant from the family of Punicaceae (Fadavi et al 2006) and Iran is the main origin of planting this fruit. In order to supply domestic and export markets, the control of effective factors in reducing fruit quality needs to be considered. Temperature management is crucial to maintain the quality of fruits during the postharvest period. This parameter should be managed using different techniques. Precooling is one of the most effective methods for enhancing the quality and freshness of the product, in which biochemical reactions and microbiological growth are reduced (Baird & Gaffney 1976; Ginsburg et al 1978; Dincer & Akaryildiz 1993; Thompson et al 1998; Brosnan & Sun 2001). Precooling methods differ based on the factors such as cooling time, water contact with product, performance of energy consumption, and rate of water loss. Given the above considerations, cooling methods can be divided into the following methods: forced air cooling, room cooling, vacuum cooling, hydrocooling, evaporative cooling, and ice cooling (Brosnan & Sun 2001)
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