Bioactive Substances in Sheep's Milk and Related Products as Components of Functional Foods

Sheep milk and its fermented products are increasingly recognized as valuable functional foods due to their high nutritional value and the presence of biologically active compounds. The aim of this review was to summarize current knowledge on selected bioactive components of sheep milk and fermented sheep milk products, with particular emphasis on their potential application as functional food ingredients and the impact of technological processes on their biological properties. The review focuses on yogurts, kefirs, and cheeses, highlighting key bioactive compounds, including peptides, lactoferrin, conjugated linoleic acid (CLA), polar lipids, orotic acid, and probiotic microorganisms. Fermentation and maturation processes contribute to the formation and transformation of bioactive compounds, which may exhibit antioxidant, antimicrobial, antihypertensive, and immunomodulatory activities, as well as support gut health and metabolic regulation. The functional potential of sheep milk products depends on milk composition, microbial activity, and processing conditions. Despite promising findings, their wider application remains limited due to seasonal availability, low production scale, and insufficient knowledge regarding bioavailability and physiological effects. Further in vivo and clinical studies are required to confirm the health-promoting potential and practical applications of fermented sheep milk products as functional food ingredients.