Sustainable Approach Through Combined Vacuum Drying and Molecular Sieves Techniques: Enhancing Quality and Efficiency in Pomegranate Aril Dehydration

Abstract

Dried vegetable products serve as nutritional supplements in various culinary, pharmacological, and cosmetic applications. Heat is generally employed as a drying agent in traditional thermal drying methods. This involves a high energy cost and significantly reduces the nutritional quality of vegetable products. This study investigates an unconventional, non-thermal drying method for pomegranate arils (PA). It is based on the use of selective molecular sieves for water molecules. This merely permits the extraction of water without compromising the other components that the fruit still contains. Compared to other dehydration techniques, this drying method uses less energy. It consumes 6.5 kWh of energy to take out 1 l of water including energy consumption for the regeneration of molecular sieves, whereas lyophilization and thermal drying procedures require 19.5 kWh and 8 kWh of energy to remove 1 l of water, respectively. Despite that, there is a lack of previous research on drying pomegranate arils using molecular sieves. Drying process studies were conducted on several characteristics, including water activity, water content, color, hardness, and size variation. It has been also investigated how pretreatments such as freezing and osmotic dehydration enhance drying. Using freezing pretreatment, the time of the drying process was reduced from 34 to 10 h, resulting in a final normalized water content (NWC) of 22.23 ± 0.75%. According to the osmotic dehydration pretreatment (OD), water lost (WL) and solid gain (SG) stabilized with values of 42.38% and 0.38% after 300 min of drying. A drying kinetic modeling study was carried out. The Midilli et al. model describes the experimental results of pomegranate arils after non-thermal drying, which have the highest R² value (0.999) and lowest RMSE (0.0060) and χ² (0.00004).