with the collaboration of Iranian Society of Mechanical Engineers (ISME)

Document Type : Research Article

Authors

1 Department of Food Science and Technology, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

2 Department of Agricultural Machinery Engineering, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Abstract

Introduction
Strawberry plays an important role in human health because of its micronutrients and natural antioxidant content. Increasing storage time and decreasing microbial processes, weight and volume, and eventually facilitating export, has bolded the need for drying this product. The most common drying method is sun drying. This technique requires large areas and lengthens the time to complete the process which is undesirable economically. Furthermore, the final product may be contaminated by dust and insects, and the exposure to solar radiation results in color deterioration. In order to improve the quality, traditional sun drying techniques can be replaced by a more rapid and efficient drying method such as hot-air drying. In recent years air impingement technology has got more attention in the field fruit slices drying due to high heat and mass transfer, decreasing drying time and increasing product quality. The objectives of this study were to investigate the effects of drying conditions on the drying kinetics and quality characteristics including the rehydration ratio of the strawberry slices in an air impingement jet dryer.
Materials and Methods
An air jet impingement dryer with controllable temperature, air velocity, and the relative nozzle-to-product distance (H/D) was used in this study. The experiments were conducted under different temperatures (45, 55, and 65°C), air velocities (6, 9, and 12 m s-1) and H/D ratios (4, 5, 6, 7, and 8). The initial moisture content, effective moisture diffusivity, activation energy, and rehydration ratio were evaluated.
Results and Discussion
The effects of drying temperature and air velocity on the moisture ratio and the drying rate are shown in Figs 2 and 3. As it can be seen, the moisture ratio of strawberry slices decreased with the increase of drying time. The analysis of variance for drying time indicated that increasing drying temperature and air velocity could reduce the drying time.  In addition, the effect of drying temperature on drying time was more significant than that of the air velocity.  It is clear that the drying rate decreased with moisture content. There was a rapid decrease in drying rate during the initial period and slow decrease at the later stages of the drying process. It is also found that the drying process generally took place in the falling rate period. It is observed that the moisture ratio decreased as H/D ratio fall. The response of drying time was affected significantly (p < 0.05) by H/D ratio. The effective moisture diffusivity increased with increasing drying temperature and air velocity. Based on the results reported in this study, the Wang and Singh model with the lowest Root Mean Square Error (RMSE=0.02) and the highest Coefficient of determination (R2=0.996) provided the best fit to describe the experimental drying data of strawberry slices. The statistical analysis shows that drying temperature and air velocity have significant (p < 0.01) effect on the rehydration ratio (RR) of slices, while the interaction effect was not significant. The means comparison shows that the RR of dried slices decreased as drying temperature and air velocity rose. H/D ratio significantly (1%) affected rehydration ratio. The means comparisons shows that the rehydration ratio increased when H/D value varied from 4 to 8. Also, the results of color change represented that color change of dried samples decreased with increase of temperature and air velocity and increased with increase of the H/D ratio.
Conclusion
a) Increasing drying temperature and air velocity dropped the drying time. In addition, the effect of drying temperature on drying time was more significant than that of the air velocity.
b) A constant rate period was not observed in drying of strawberry slices and the whole process of strawberry slices was carried out in the falling rate period.
c) The moisture ratio decreased as H/D ratio dropped, which in turn resulted in saving drying times.
d) The Wang and Singh model was found to be the best model to describe the drying kinetics of strawberry slices.
e) The effective moisture diffusivity of strawberry slices ranged from 1.62×10-10 to 3.24×10-10 m2 s-1.
f) The values of activation energy of strawberry slices were found to be 12.88, 15.055 and 16.746 kJ mol-1 for air velocities of 6, 9 and 12 m s-1, respectively.
g) The rehydration ratio of dried slices dropped as the drying temperature and air velocity rose and increased with increase of the H/D ratio.
h) The color change of dried samples decreased with the increase of temperature and air velocity and increased with the increase of the H/D ratio.

Keywords

Open Access

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1. Alnak, D. E., and K. Karabulut. 2018. Analysis of heat and mass transfer of the different moist object geometries with air slot jet impinging for forced convection drying. Thermal Science 22: 2943-2953.
2. Alonzo-Macias, M., A. Cardador-Martinez, S. Mounir, G. Montejano-Gaitan, and K. Allaf. 2013. Comparative study of the effects of drying methods on antioxidant activity of dried strawberry (Fragaria Var. Camarosa). Journal of Food Research 2: 92.
3. Banooni, S., S. M. Hosseinalipour, A. S. Mujumdar, P. Taherkhani, and M. Bahiraei. 2009. Baking of flat bread in an impingement oven: modeling and optimization. Drying Technology 27: 103-112.
4. Caixeta, A. T., R. G. Moreira, and M. E. Castell-Perez. 2002. Impingement drying of potato chips. Journal of Food Process Engineering 25: 63-90
5. Chakroun, W. M., A. A. Abdel-Rahman, and S. F. Al-Fahed, 1998. Heat transfer augmentation for air jet impinged on a rough surface. Applied Thermal Engineering 18 (12): 1225-1241.
6. Cunningham, S., W. Mcminn, T. Magee, and P. Richardson. 2008. Experimental study of rehydration kinetics of potato cylinders. Food and Bioproducts Processing 86: 15-24.
7. Dikbasan, T. 2007. Determination of effective parameters for drying of apples. Izmir Institute of Technology.
8. Doymaz, I. 2004. Effect of pre-treatments using potassium metabisulphide and alkaline ethyl oleate on the drying kinetics of apricots. Biosystems Engineering 89: 281-287.
9. Doymaz, I. 2008. Convective drying kinetics of strawberry. Chemiacal. Engineering and Processing 47: 914-919.
10. Giampieri, F., T. Y. Forbes-Hernandez, M. Gasparrini, J. M. Alvarez-Suarez, S. Afrin, S. Bompadre, J. L. Quiles, B. Mezzetti, and M. Battino. 2015. Strawberry as a health promoter: an evidence based review. Food & Function 6: 1386-1398.
11. Hafezi, N., M. J. Sheikhdavoodi, S. M. Sajadiye, and M. E. Khorasani Ferdavani. 2016. The study of some physical properties and energy aspects of potatoes drying process by the infrared-vacuum method. Journal of Agricultural Machinery 6 (2): 463-475. (In Farsi).
12. Hassan-Beygi, S., M. Aghbashlo, M. Kianmehr, and J. Massah. 2009. Drying characteristics of walnut (Juglans regia L.) during convection drying. International Agrophysics 23: 129-135.
13. Huang, D., W. Li, H. Shao, A. Gao, and X. H. Yang. 2017. Colour, texture, microstructure and nutrient retention of Kiwifruit slices subjected to combined air-impingement jet drying and freeze drying. International Journal of Food Engineering 13 (7). https://doi.org/10.1515/ijfe-2016-0344.
14. Khodabakhsh, S., A. R. Yousefi, M. Mohebbi, S. M. A. Razavi, A. Orooji, and M. R. Akbarzadeh-Totonchi. 2015. Modeling for drying kinetics of papaya fruit using fuzzy logic table look-up scheme. International Food Research Journal 22: 1234-1239.
15. Johnson, A. C., and E. M. A. Almukhaini. 2016. Drying studies on peach and strawberry slices. Cogent Food & Agriculture 2: 1-9
16. Lee, G. H., and F. H. Hsieh. 2008. Thin layer drying kinetics of strawberry fruit leather. Transactions of the ASABE 51:1699-1705.
17. Lee, J., Z. Ren, P. Ligrani, D. H. Lee, M. D. Fox, and H. K. Moon. 2014. Cross-flow effects on impingement array heat transfer with varying jet-to-target plate distance and hole spacing. International Journal of Heat and Mass Transfer 75: 534-544.
18. Li, W., L. Yuan, X. Xiao, and X. Yang .2016. Dehydration of kiwifruit (Actinidia deliciosa) slices using heat pipe combined with impingement technology. International Journal of Food Engineering 12: 265-276.
19. Li, W., M. Wang, X. Xiao, B. Zhang, and X. Yang. 2015. Effects of air-impingement jet drying on drying kinetics, nutrient retention and rehydration characteristics of Onion (Allium cepa) slices. International Journal of Food Engineering 11: 435-446.
20. Li, X. D., M. Alamir, E. Witrant, G. Della-Valle, O. Rouaud, L. Boillereaux, and, C. Josset. 2013. Further investigations on energy saving by jet impingement in bread baking process. 5th Symposium on System Structure and Control, 696-701, Grenoble, France, February 4-6: 2013
21. Lopez‐Quiroga, E., V. Prosapio, P. J. Fryer, I. T. Norton, and S. Bakalis. 2019. Model discrimination for drying and rehydration kinetics of freeze‐dried tomatoes. Food Process Engineering: e13192.
22. Madamba, P. S., R. H. Driscoll, and K. A. Buckle. 1996. The thin-layer drying characteristics of garlic slices. Journal of Food Engineering 29: 75-97.
23. Midilli, A., H. Kucuk, and Z. Yapar. 2002. A new model for single-layer drying. Drying technology 20: 1503-1513.
24. Mirzaee, E., S. Rafiee, A. Keyhani, and Z. Emam-Djomeh. 2009. Determining of moisture diffusivity and activation energy in drying of apricots. Research in Agricultural Engineering 55: 114-120.
25. Mohammadi, I., R. Tabatabaekoloor, and A. Motevali. 2019. Effect of air recirculation and heat pump on mass transfer and energy parameters in drying of kiwifruit slices. Energy 170: 149-158.
26. Morris, C. E. 1994. Efficient cookers, dryers and fryers. Journal of Food Engineering 10: 115-120.
27. Mujumdar, A. S. 2006. Impingement drying. In Mujumdar, A. S. (Ed.) Handbook of Industrial Drying third edn (UK: Taylor and Francis).
28. Mwithiga, G., and J. O. Olwal. 2005. The drying kinetics of kale (Brassica oleracea) in a convective hot air dryer. Journal of Food Engineering 71: 373-378.
29. Obot, N. T., and T. A. Trabold. 1987. Impingement heat transfer within arrays of circular jets: part 1-effects of minimum, intermediate, and complete crossflow for small and large spacings. Journal of Heat Transfer 109: 872-879.
30. Orsat, V., V. Changrue, and G. V. Raghavan. 2006. Microwave drying of fruits and vegetables. Stewart Post-Harvest Rev 6: 4-9.
31. Qiu, G., D. Wang, X. Song, Y. Deng, and Y. Zhao. 2018. Degradation kinetics and antioxidant capacity of anthocyanins in air-impingement jet dried purple potato slices. Food Research International 105: 121-128.
32. Radhika, G., S. Satyanarayana, and D. Rao. 2011. Mathematical model on thin layer drying of finger millet (Eluesine coracana). Advance Journal of Food Science and Technology 3: 127-131.
33. Rao, M. 1986. Rheological properties of fluid foods. Engineering Properties of Foods: 1-47.
34. Sadin R., G. R. Chegini, and H. Sadin. 2014. The effect of temperature and slice thickness on drying kinetics tomato in the infrared dryer. Heat and Mass Transfer 50: 501-507.
35. Sagar, V., and P. S. Kumar. 2010. Recent advances in drying and dehydration of fruits and vegetables: a review. Journal of Food Science and Technology 47: 15-26.
36. Sarkar, A., N. Nitin, M. V. Karwe, and R. P. Singh. 2004. Fluid Flow and Heat Transfer in Air Jet Impingement. Food Processing 69: 113-122.
37. Sarkar, A., and R. P. Singh. 2004. Air impingement technology for food processing: visualization studies. LWT-Food Science and Technology 37: 873-879.
38. Wae-hayee, M., P. Tekasakul, and C. Nuntadusit. 2013. Influence of nozzle arrangement on flow and heat transfer characteristics of arrays of circular impinging jets. Songklanakarin Journal of Science & Technology 35.
39. Wang, D., J. W. Dai, H. Y. Ju, L. Xie, H. W. Xiao, Y. H. Liu, and Z. J. Gao. 2015. Drying kinetics of American ginseng slices in thin-layer air impingement dryer. International Journal of Food Engineering 11: 701-711.
40. Xiao, H. W., J. W. Bai, L. Xie, D. W. Sun, and Z. J. Gao. 2015. Thin-layer air impingement drying enhances drying rate of American ginseng (Panax quinquefolium L.) slices with quality attributes considered. Food and Bioproducts Processing 94: 581-591.
41. Xiao, H. W., C. L. Pang, L. H. Wang, J. W. Bai, W. X. Yang, and Z. J. Gao. 2010a. Drying kinetics and quality of Monukka seedless grapes dried in an air-impingement jet dryer. Biosystems Engineering 105: 233-240.
42. Xiao, H. W., Z. J. Gao, H. Lin, and W. X. Yang. 2010b. Air impingement drying characteristics and quality of carrot cubes. Journal of Food Process Engineering 33: 899-918.
43. Xiao, H. W., S. X. Zhang, J. W. Bai, X. M. Fang, Z. J. Zhang, and Z. J. Gao. 2010c. Air impingement drying characteristics of apricot. Transactions of the Chinese Society of Agricultural Engineering 26: 318-323.
44. Xiao, H. W., X. D. Yao, H. Lin, W. X. Yang, J. S. Meng, and Z. J. Gao. 2012. Effect of SSB (superheated steam blanching) time and drying temperature on hot air impingement drying kinetics and quality attributes of yam slices. Journal of Food Process Engineering 35: 370-390.
45. Yaldiz, O., C. Ertekin, and H. I. Uzun. 2001. Mathematical modeling of thin layer solar drying of sultana grapes. Energy 26: 457-465.
46. Zhang, Q., and J. B. Litchfield. 1991. An optimization of intermittent corn drying in a laboratory scale thin layer dryer. Drying Technology 9: 383-395.
47. Zheng, X., H. W. Xiao, L. Wang, Q. Zhang, J. Bai, L. Xie, H. Ju, and Z. J. Gao. 2014. Shorting drying time of Hami-Melon slice using infrared radiation combined with air impingement drying. Transactions of the Chinese Society of Agricultural Engineering 30: 262-269.
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