A review of solar and solar-assisted drying of fresh produce: state of the art, drying kinetics, and product qualities

Global demand exists for high-quality fresh produce. Nevertheless, the quality of fresh produce is severely impacted by its perishability due to its high moisture content. Therefore, fresh produces are preserved using artificial dryers (hot-air dryers, catalytic infrared dryers, etc.) driven by electricity or natural fuels. Nonetheless, the exorbitant cost of power has heightened the need for sustainable resources, notably solar energy, for drying. Hence, this article is a review of how solar dryers and solar-assisted dryers have affected the drying kinetics and quality of fresh produce in the last 5 years. The review showed that solar drying modeling technology (thin-layer modeling, computational fluid dynamics, adaptive-network-based fuzzy interference system, artificial neural network) helps examine fresh produce drying characteristics using various simulation tools before developing any procedure. Solar-assisted drying shortens drying times and increases drying rates. Besides, the quality of the dried fresh produce (color, aroma, appearance, rehydration, etc.) should always be considered. Hybrid solar drying produces higher drying rates and product quality than other solar dryers. However, energy analysis needs to be done as several studies have recognized energy efficiency and product quality. In addition, fresh produce must be pre-treated before solar drying to maintain the final product quality. Therefore, future studies should focus on creating other pretreatment techniques to produce the needed chemical and physical changes and enhance mass and heat transfer. Finally, the influence of solar drying on the final products' nutrient retention or loss, functionalities, or sensory characteristics needs further investigation and comparison to other non-solar drying technologies. (c) 2023 Society of Chemical Industry.