Abstract
Animal by-products offer a promising solution for growing global protein demand. Keratin is one of the most abundant proteins in animal by-products. Dietary keratin is gaining attention as an alternative protein source with potential applications in nutricosmetics, nutraceuticals, prebiotics, and food packaging. Keratin is naturally water-insoluble and indigestible, necessitating harsh extraction techniques that reduce palatability, digestibility, bioavailability, and alter nutritive composition, making it unsuitable for human consumption. Consequently, the dietary use of keratin remains understudied. Emerging technologies claim to produce dietary keratin with improved nutritional quality. Therefore, this review explores keratin sources, safe extraction methods and the nutritive composition of keratin products successfully used in dietary purposes, while consolidating findings of in vitro and in vivo toxicity, digestibility, and bioavailability. The strengths, challenges, limitations of current approaches, and future directions are discussed. Dietary keratins are a nutritive, safe alternative protein best extracted from wool by microwaving or feathers by acid/alkaline hydrolysis.
• Wool and feather keratin are promising sources for dietary keratin extraction.
• Keratin extracts are rich in protein, amino acids, micro and macro minerals.
• In vitro/in vivo studies show keratin is non-cytotoxic, digestible, and bioavailable
• Keratin act as prebiotics, improving gut morphology and supporting microbiota.
• Dietary keratin extraction best achieved by acid/alkaline hydrolysis or microwaving.