An Evaluation of the Performance of Forced Air Cooling on Cooling Parameters in Transient Heat Transfer at Different Layers of Pomegranate

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. 

Keywords

• Precooling; Forced air cooling; Heat transfer; Pomegranate

References

1. Baird C D & Gaffney J J (1976). A numerical procedure for calculating heat transfer in bulk loads of fruits or vegetables. ASHRAE Transactions 82(2): 525-540
2. Brosnan T & Sun D (2001). Precooling techniques and applications for horticultural products-a review. International Journal of Refrigeration 32: 154-170
3. Castro L R, Vigneault C & Cortez L A B (2004). Effect of container opening area on air distribution during precooling of horticultural produce. Transactions of the ASAE 47(6): 2033-2038
4. Castro L R, Vigneault C & Cortez L A B (2005). Cooling performance of horticultural produce in containers with peripheral openings. Postharvest Biology and Technology 38: 254-261
5. Dehghannya J, Ngadi M &Vigneault C (2011). Mathematical modeling of airflow and heat transfer during forced convection cooling of produce considering various package vent areas. Food Control 22: 1393-1399
6. Dennis C (1984). Effect of storage and distribution conditions on the quality of vegetables. Acta Horticulturae 163: 85-104 Dincer I (1995). Airflow precooling of individual grapes. Journal of Food Engineering 26: 243-249
7. Dincer I & Akaryildiz E (1993). Transient temperature distributions within spherical products with internal heat generation and transpiration. International Journal of Heat and Mass Transfer 36: 1998-2003
8. Emond J P, Mercier F, Sadfa S O, Bourre M & Gakwaya A (1996). Study of parameters affecting cooling rate and temperature distribution in forced air precooling of strawberry. Transactions of the ASAE 39(6): 21852191

9. Fadavi A, Barzegar M & Azizi M H (2006). Determination of fatty acids and total lipid content in oilseed of 25 pomegranates varities grown in Iran. Journal of Food Composition Analysis 19: 676-680
10. Ginsburg L, Combrink J C & Truter A B (1978). Long and short term storage of table grapes. International Journal of Refrigeration 1(3): 137-142
11. Golob P, Farrell G & Orchard G E (2002). Crop Postharvest Science and Technology, Principles and Practices. Volume 1. Blackwell Publishing Company, Oxford, UK, pp. 554
12. Goyette B, Vigneault C, Panneton B & Raghavan G S V (1996). Method to evaluate the average temperature at the surface of horticultural crop. Canadian Agricultural Enigineering 38(4): 291-295
13. Guillou R (1960). Forced air fruit cooling Transactions of the ASAE 3(2): 16-18
14. Hass E, Felsenstein G, Shitzer A & Manor G (1976). Factors affecting resistance to airflow through packed fresh fruit. ASHRAE Transactions 82(2): 548-554
15. Henry F E & Bennett A H (1973). Hydraircooling vegetables products in unit loads. Transactions of the ASAE 16(40): 731-739
16. Kader A A (2002). Posthaevest technology of horticultural crops. Cooperative Extension of University of California, Division of Agricultural and Natural Resources, University of California,
17. Davis, CA, Publication No. 3311 Kumar R, Kumar A & Murthy U N (2008). Heat transfer during forced air precooling of perishable food products. Biosystems Engineering 99: 228-233
18. Lambrinos G, Assimaki H, Manolopoulou H, Sfakiotakis E & Porlimgis J (1997). Air precooling and hydrocooling of Hayward Kiwifruit. Acta Horticulturae 444: 561-566
19. Lindsay R T, Neale M A & Messer H J M (1983). Ventilation rates for positive ventilation of vegetables in bulk bins. Journal of Agricultural Engineering Research 28(1): 33-44
20. Ngcobo M E K, Delele M A, Opera U L & Meyer C J (2013). Performance of multi-packaging for table grapes based on airflow, cooling rates and fruit quality. Journal of Food Engineering 116: 613-621
21. Thompson J F, Mitchel F G, Rumsey T R, Kasmire R F & Crisosto C H (1998). Commercial cooling of fruits, vegetables, and flowers. University of California, Agriculture and Natural Resources, Davis, DANR Publication 21567