Tropical fruit peels as functional food ingredients: unlocking antioxidant and anti-glycation potential through innovative drying

Introduction The upcycling of food waste into natural sources of functional food ingredients presents a sustainable strategy to reduce environmental pollution while adding value to agro-industrial byproducts. This study evaluated the impact of different drying methods on the extraction of phytochemicals with antioxidant and anti-glycation activities from tropical fruit peels. Methods The peel samples of Carica papaya , Citrus limon , Hylocereus polyrhizus , Musa acuminata , and Persea americana were dried with four different methods, namely freeze-drying, microwave drying, hot air oven drying, and microwave-assisted hot air oven drying. The moisture content, browning index, total phenolics, flavonoids, tannin, polysaccharides, ascorbic acid equivalents, reducing potential, radical scavenging, and anti-glycation activities of the dried peel samples were quantified with colorimetric method and compared with their fresh counterparts via chemometric analysis. Results and discussion The drying process significantly enhanced ( p < 0.05) the antioxidant and anti-glycation potential of fruit peels by at least 67.3 and 15.2%, respectively, when compared to fresh counterparts. Among the four drying methods, hot air oven drying produced the highest browning index in P. americana and M. acuminata samples. Microwave-assisted hot air oven drying yielded the greatest amounts of total phenolics and polysaccharides in C. papaya , while microwave drying maximized antioxidant and anti-glycation activities in H. polyrhizus . Freeze-drying preserved the highest ascorbic acid equivalents in C. limon and achieved the highest levels of polyphenols and ascorbic acid equivalents in M. acuminata . Principal component analysis revealed that fruit species and drying techniques accounted for 74.6 and 13.5% of the total variation in bioactivity, respectively. This study showed that, when properly processed, dried fruit peels have significant potential as natural functional ingredients for food and nutraceutical applications. It emphasizes the key role of drying not just as a preservation method, but as a strategy for enhancing functional properties.