Nutritional and Chemical Characterization of Red and Purple Potatoes Peels: A Polyphenol-Rich By-Product

Potato peel represents a major by-product of the potato-processing industry and a promising source of bioactive compounds with potential health benefits. This study investigates the biochemical and nutritional composition of peels from five purple and two red potato cultivars, with particular attention to their phytochemical profiles and antioxidant properties. Total phenolic content, carbohydrates, proteins, and lipids were quantified using UV–visible spectrophotometry. The phytochemical composition was further characterized via High-Performance Liquid Chromatography coupled with a Diode-Array Detector (HPLC-DAD). Antioxidant and radical-scavenging capacities of the extracts were assessed through Ferric Reducing Antioxidant Power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Significant variability was observed across cultivars for all measured parameters. While all samples were rich in carbohydrates and proteins, they shared a common phenolic profile dominated by chlorogenic acid and its derivatives, as well as caffeic acid. Anthocyanin composition, however, was highly cultivar-specific. Notably, all extracts demonstrated strong antioxidant and antiradical activities, in agreement with their high total phenolic content. These findings highlight the potential of red and purple potato peels as valuable sources of functional ingredients for food and nutraceutical applications.