Biologically active peptides released in fermented milk: role and functions

Abstract

Recent years have seen a growing interest in the health enhancement effects of lactic acid bacteria (LAB). More evidence is accumulating that probiotics—foods that contain live bacteria—might constitute a valuable therapeutic and preventive tool against a number of diseases in humans and in animals. Probiotics confer on their host multiple beneficial effects including prevention and treatment of diarrhea, induction of protective immunity against pathogens and tumors, prevention of allergies, controlling inflammatory diseases, modulating gastrointestinal functions, and alleviation of lactose intolerance and hypertension. Numerous health and functional attributes of fermented dairy products are ascribed to the microorganisms that induce physical and chemical modifications of milk components. The mechanism responsible for health benefits of LAB is multifactorial, and probably relates to the complex interaction between milk components, LAB and their constituents, and the intestinal mucosa. Recent studies have reported the particular role of the metabolic products derived from milk fermentation by probiotics. An important metabolic activity that occurs during milk fermentation is proteolysis. Proteolysis ensures LAB growth in the medium, and consequently, might influence the potential release of physiologically active peptides. These peptides are encrypted in the milk protein sequences in a latent state, and might be released during food processing or after degradation by digestive enzymes. They have been shown to possess opiate, antithrombotic, antihypertensive, immunomodulating, antibacterial, antigastric, and mineral carrier properties. Hence, milk-related bioactive peptides, and other derived metabolites from fermentation, might play an important role in health enhancement and reducing the incidence of many diseases. Physiologically active peptides might particularly contribute to the phenomenon of probiotics due to their hormone-like activities. Many of these sequences can be found in the milk of a large number of mammalian species. Some multifunctional bioactive sequences present in overlapping sequence, in the β-caseins for example, are endowed with multiple physiological activities (morphinomimetic and immunomodulating). Bioactive sequences are also found in plant and animal proteins as immunomodulating peptides in soybean and rice albumin. Several peptides derived from milk proteins that have effects on behavioral, neurological, physiological, and vasoregulatory responses have been identified. Table 7.1 lists the major peptides identified in cows’ milk and their physiological activities. This chapter will review the occurrence of biologically active peptides in fermented milk and their functional and potential physiological activities, specifically opioid, antihypertensive, and immunomodulating activities.