Optimization of Intermittent Drying of Rehydrated Dates

Abstract

The intermittent drying of dates remains a neglected area in academic research, primarily due to factors such as varying cultivation patterns across regions and limited attention to the valorization of overdried dates. This study investigates the impact of drying parameters: air temperature, air velocity, and intermittency ratio, on the drying time and energy consumption of rehydrated dates using hot air drying. Employing Response Surface Methodology with a Central Composite Design and a desirability function, experiments were conducted within specific ranges of air temperatures (40–70 °C), air velocities (0.5–5 m/s), and intermittency ratios (0.2–1). Results show that while air velocity minimally affects drying time, it negatively influences energy efficiency. Conversely, air temperature is significant for both responses. Reducing the intermittency ratio from 1 to 0.3 resulted in a decrease in total energy consumption by up to 60%, particularly at lower temperatures, with negligible impact on total drying time. The study identifies optimal conditions for minimizing both drying time and energy consumption as an inlet temperature of 66 °C, air velocity of 2.5 m/s, and an intermittency ratio of 0.7. The experimental data were fitted to 7 mathematical drying models, the results indicated that Midilli-Kucuk model gave better performance to define the drying kinetics of intermittent drying of rehydrated dates.

Keywords

• Intermittent drying
• hot air dryer
• response surface methodology
• rehydrated dates

References

1. K. D. Alotaibi et al., "Date palm cultivation: A review of soil and environmental conditions and future challenges," Land Degradation & Development, vol. 34, no. 9, pp. 2431-2444, May. 2023, doi: https://doi.org/10.1002/ldr.4619.
2. Z.-X. Tang, L.-E. Shi, and S. M. Aleid, "Date fruit: chemical composition, nutritional and medicinal values, products," Journal of the Science of Food and Agriculture, vol. 93, no. 10, pp. 2351-2361, Aug. 2013, doi: https://doi.org/10.1002/jsfa.6154.
3. A. Boubekri, H. Benmoussa, F. Courtois, and C. Bonazzi, "Softening of Overdried ‘Deglet Nour’ Dates to Obtain High-Standard Fruits: Impact of Rehydration and Drying Processes on Quality Criteria," Drying Technology, vol. 28, no. 2, pp. 222-231, 2010, doi: 10.1080/07373930903526764.
4. D. Mennouche, B. Bouchekima, A. Boubekri, S. Boughali, H. Bouguettaia, and D. Bechki, "Valorization of rehydrated Deglet-Nour dates by an experimental investigation of solar drying processing method," Energy Conversion and Management, vol. 84, pp. 481-487, 2014, doi: 10.1016/j.enconman.2014.04.067.
5. K. J. Chua, A. S. Mujumdar, S. K. Chou, M. N. A. Hawlader, and J. C. Ho, "Convective Drying of Banana, Guava and Potato Pieces : Effect of Cyclical Variations of Air Temperature on Drying Kinetics and Color Change," Drying Technology, vol. 18, no. 4-5, pp. 907-936, 2000, doi: 10.1080/07373930008917744.
6. A. Mukhtar, S. Latif, A. Salvatierra-Rojas, and J. Müller, "Catalase Activity in Hot-Air Dried Mango as an Indicator of Heat Exposure for Rapid Detection of Heat Stress," Applied Sciences, vol. 12, no. 3, doi: 10.3390/app12031305.
7. Y. K. Pan, L. J. Zhao, and W. B. Hu, "The Effect of Tempering-Intermittent Drying on Quality and Energy of Plant Materials," Drying Technology, vol. 17, no. 9, pp. 1795-1812, 1998, doi: 10.1080/07373939908917653.
8. A. Singh, J. Sarkar, and R. R. Sahoo, "Experimentation and Performance Analysis of Solar-Assisted Heat Pump Dryer for Intermittent Drying of Food Chips," Journal of Solar Energy Engineering, vol. 144, no. 2, 2021, doi: 10.1115/1.4052549.

9. N. Ben Mustapha, I. Boumnijel, and D. Mihoubi, "Tempering Drying and Energy Consumption," Journal of Heat Transfer, vol. 144, no. 10, 2022, doi: 10.1115/1.4055045.
10. R. Md Saleh, B. Kulig, A. Emiliozzi, O. Hensel, and B. Sturm, "Impact of critical control-point based intermittent drying on drying kinetics and quality of carrot (Daucus carota var. laguna)," Thermal Science and Engineering Progress, vol. 20, 2020, doi: 10.1016/j.tsep.2020.100682.
11. J. C. Alves Pereira et al., "Continuous and Intermittent Drying of Rough Rice: Effects on Process Effective Time and Effective Mass Diffusivity," Agriculture, vol. 10, no. 7, 2020, doi: 10.3390/agriculture10070282.
12. M. A. Kherrafi et al., "Performance enhancement of indirect solar dryer with offset strip fins: Experimental investigation and comparative analysis," Solar Energy, vol. 266, p. 112158, Dec 2023, doi: 10.1016/j.solener.2023.112158.
13. A. Benseddik, A. Azzi, M. N. Zidoune, and K. Allaf, "Mathematical empirical models of thin-layer airflow drying kinetics of pumpkin slice," Engineering in Agriculture, Environment and Food, vol. 11, no. 4, pp. 220-231, 2018, doi: 10.1016/j.eaef.2018.07.003.
14. S. Rafiee, "Thin Layer Drying Properties of Soybean (Viliamz Cultivar)," Journal of Agricultural Science and Technology, (in eng), vol. 11, no. 3, pp. 301-308, 2009. [Online]. Available: http://jast.modares.ac.ir/article-23-1698-en.html.
15. H. Toğrul, "Suitable drying model for infrared drying of carrot," Journal of Food Engineering, vol. 77, no. 3, pp. 610-619, 2006, doi: 10.1016/j.jfoodeng.2005.07.020.
16. T. Gunhan, V. Demir, E. Hancioglu, and A. Hepbasli, "Mathematical modelling of drying of bay leaves," Energy Conversion and Management, vol. 46, no. 11-12, pp. 1667-1679, 2005, doi: 10.1016/j.enconman.2004.10.001.
17. G. Zhanyong, J. Shaohua, L. Ting, P. Jinhui, Z. Libo, and J. Feng, "Optimization on Drying of CuCl Residue by Hot-Air Using Response Surface Methodology," in Drying, Roasting, and Calcining of Minerals, T. P. Battle et al. Eds. Cham: Springer International Publishing, 2016, pp. 73-80. doi: 10.1007/978-3-319-48245-3_9.
18. S. Chouicha et al., "Valorization Study of Treated Deglet-nour Dates by Solar Drying Using Three Different Solar Driers," Energy Procedia, vol. 50, pp. 907-916, 2014, doi: 10.1016/j.egypro.2014.06.109.
19. K. O. Falade and E. S. Abbo, "Air-drying and rehydration characteristics of date palm (Phoenix dactylifera L.) fruits," Journal of Food Engineering, vol. 79, no. 2, pp. 724-730, 2007, doi: 10.1016/j.jfoodeng.2006.01.081.
20. G. J. Swamy and K. Muthukumarappan, "Optimization of continuous and intermittent microwave extraction of pectin from banana peels," Food Chemistry, vol. 220, pp. 108-114, Apr. 2017, doi: 10.1016/j.foodchem.2016.09.197.
21. N. Aghilinategh, S. Rafiee, S. Hosseinpur, M. Omid, and S. S. Mohtasebi, "Optimization of intermittent microwave-convective drying using response surface methodology," Food Sci Nutr, vol. 3, no. 4, pp. 331-41, Jul. 2015, doi: 10.1002/fsn3.224.
22. W. K. Lewis, "The Rate of Drying of Solid Materials," Journal of Industrial & Engineering Chemistry, vol. 13, no. 5, pp. 427-432, May. 1921, doi: 10.1021/ie50137a021.
23. G. Xanthopoulos, G. Lambrinos, and H. Manolopoulou, "Evaluation of Thin-Layer Models for Mushroom (Agaricus bisporus) Drying," Drying Technology, vol. 25, no. 9, pp. 1471-1481, Sep. 2007, doi: 10.1080/07373930701537179.
24. A. Midilli, H. Kucuk, and Z. Yapar, "A New Model For Single-Layer Drying," Drying Technology, vol. 20, no. 7, pp. 1503-1513, Jul. 2002, doi: 10.1081/DRT-120005864.
25. Q. Zhang and J. B. Litchfield, "An Optimization Of Intermittent Corn Drying In A Laboratory Scale Thin Layer Dryer," Drying Technology, vol. 9, no. 2, pp. 383-395, Mar. 1991, doi: 10.1080/07373939108916672.
26. O. Yaldýz and C. Ertekýn, "Thin Layer Solar Drying Of Some Vegetables," vol. 19, pp. 583 - 597, 2001, doi : doi: 10.1081/DRT-100103936. O. Yaldiz, C. Ertekin, and H. I. Uzun, "Mathematical modeling of thin layer solar drying of sultana grapes," Energy, vol. 26, no. 5, pp. 457-465, May. 2001, doi: 10.1016/S0360-5442(01)00018-4.
27. M. H. Masud, M. U. H. Joardder, A. A. Ananno, and S. Nasif, "Feasibility study and optimization of solar-assisted intermittent microwave–convective drying condition for potato," European Food Research and Technology, vol. 248, no. 5, pp. 1335-1349, May. 2022, doi: 10.1007/s00217-022-03957-5.
28. M. Kaveh, Y. Abbaspour‐Gilandeh, H. Fatemi, and G. Chen, "Impact of different drying methods on the drying time, energy, and quality of green peas," Journal of Food Processing and Preservation, vol. 45, no. 6, 2021, doi: 10.1111/jfpp.15503.
29. H. Majdi, J. A. Esfahani, and M. Mohebbi, "Optimization of convective drying by response surface methodology," Computers and Electronics in Agriculture, vol. 156, pp. 574-584, 2019, doi: 10.1016/j.compag.2018.12.021.
30. S. P. Ong, C. L. Law, and C. L. Hii, "Optimization of Heat Pump–Assisted Intermittent Drying," Drying Technology, vol. 30, no. 15, pp. 1676-1687, 2012, doi: 10.1080/07373937.2012.703741.
31. W. Hajji and S. Bellagha, "New Emerging Technique to Intensify Convective Air Drying Process: Impact of Interval Starting Accessibility Drying (ISAD) on Quality Attributes of Strawberries Fruits," International Journal of Innovative Approaches in Agricultural Research, vol. 7, no. 3, pp. 252-259, 2023, doi: 10.29329/ijiaar.2023.602.1.
32. M. Beigi, "Energy efficiency and moisture diffusivity of apple slices during convective drying," Food Science and Technology, vol. 36, 2016, doi: 10.1590/1678-457X.0068.
33. W. Hajji, S. Bellagha, and K. Allaf, "Energy-saving new drying technology: Interval starting accessibility drying (ISAD) used to intensify dehydrofreezing efficiency," Drying Technology, vol. 40, no. 2, pp. 284-298, 2020, doi: 10.1080/07373937.2020.1788072.