Valorization of fruits, vegetables, and their by-products: Drying and bio-drying

Due to increasing awareness of food sustainability and security among consumers and food manufacturers, the valorization of food products has gained huge interest among researchers with the aim to diversify the product range, including those processed from the by-products. From the United Nations (UN) Environment Programme's Food Waste Index Report 2021, the wastage of foods reaches 931 million tonnes each year. To align with the UN Sustainable Development Goals, which aim to halve food waste by 2030, food wastage reduction, especially from fruits and vegetables that have a short shelf life, can be processed into a stable value-added product. Hence, the application of various drying methods on fruits, vegetables, and their by-product were conducted as measures to decrease or avoid possible wastage. In this article, the applications of sun drying, solar drying, convective air drying, hybrid drying, spray drying, drum drying, vacuum drying, freeze-drying, and refractance window drying as means of food valorization strategy and impacts on the physical, chemical, microbiological, and nutritional properties are compiled and reviewed. In addition, bio-drying processes were also presented to reduce the generation of food waste and environmental impact.