From peel to power: Exploring the potential of fruit waste in a circular economy

• Fruit waste is a rich source of bioactive compounds. • Fermented fruit residues yield SCP, meeting sustainable protein needs. • Fruit waste-derived aerogels aid in pollution control, especially in dye removal. • Valorisation drives a circular economy, achieving zero-waste goals and ecobenefits. Fruits are vital for a balanced diet due to their rich natural antioxidant content, which has been demonstrated to be effective in managing various chronic disorders. The several types of waste produced by the fruit industry are seen as an international issue. As a rich source of secondary metabolites, fruit waste offers an opportunity for the sustainable use of waste materials, helping to attain the global objective of “zero waste.” Fruit waste includes a variety of phytochemicals, including colours, and other valuable substances, including polyphenols and polysaccharides. The use of phenolic compounds in functional meals and nutritional supplements has made them more desirable to the business. The single-cell protein (SCP) technique has recently gained popularity as a solution to two key problems: the growing global protein shortage resulting from population growth, and the significant increase in industrial waste production rates. Over the years, fruit production has expanded worldwide. Fruit wastes unsuitable for consumption are often discarded into the environment, causing environmental pollution. However, these residues are rich in fermentable sugars and essential nutrients that microorganisms can use as substrates to produce microbial products such as protein, bioethanol and biogas. This review investigates the utilisation of fruit wastes as a substrate for SCP creation in light of this. Plant- and animal-based functional food components, including omega-3 fatty acids, soy protein isolate, whey protein isolate, and dietary fibre, have been widely utilised to produce essential food products. Most byproducts of fruit processing, including those from oranges, apples, and grapes, are rich in dietary fibre, unsaturated fatty acids, and bioactive phytochemicals, making them potentially useful in functional foods. Currently, integrated and multidisciplinary approaches are being employed to investigate the key components and related bioactivities of fruit waste, exploring new application areas and creating value in terms of social, environmental, and economic aspects, thereby developing an environmentally friendly method for handling fruit waste. Thus, this review aims to present comprehensive information on the bioactive chemicals, antioxidants, and antiviral activity found in fruit waste, as well as value-added products, including polyphenols, single-cell proteins, bioethanol, and bioplastic enzymes.