Bioactive peptides from proteins have been found in a range of food products such as milk and muscle sources (fish, beef, pork and chicken). Bioactive peptides from food proteins can offer some protective and health benefits in the body. These include antihypertensive, antimicrobial, antioxidant and prebiotic effects. Bioactive peptides remain inactive when they are bound within the food proteins. They can be biologically active when they are released from the sequence of the parent proteins.
The activity of peptides highly relies on the structure of their amino acid constituents in terms of sequence and size. The sequences of amino acids vary in length; usually between 2 and 20 amino acids residues. Food-derived bioactive peptide was first introduced when the ability of casein-based phosphorylated peptides in increasing vitamin D-independent calcification in rachitic infants was reported by Mellander in 1950.
To date, the most widely identified bioactive peptides from milk and muscles have been found to be antihypertensive; in particular those which are inhibitory to the activity of angiotensin-1-converting enzyme (ACE). The significance of the unique health benefits of the released bioactive peptides has led the researchers to focus on finding effective techniques for the liberation of bioactive peptides from the food proteins.
During the last two decades many studies have been carried out to investigate efficient strategies to release bioactive peptides from milk and muscles. Bioactive peptides can be isolated in different ways which mainly consist of the enzymatic hydrolysis of the whole protein, microbial fermentation and food processing. Enzymatic hydrolysis of protein develops in response to the activity of digestive enzymes (e.g. pepsin, trypsin and chymotrypsin) which can facilitate the isolation of active peptide fragments.
Microbial fermentation is based on proteolytic activities of the starter and non-starter micro-organisms including Lactobacillus helveticus, Lactobacillus acidophilus, Lactobacillus plantarum, Lactococcus lactis and Streptococcus thermophilus which are applied to the manufacturing of fermented dairy products. Bioactive peptides are also released as a result of chemical/structural changes of the protein constituents of the processed foods. For instance, cheese provides a good source of phosphopeptides (as natural compositions). Furthermore, the secondary proteolytic process of cheese ripening can enhance the formation of peptides which are able to inhibit the activities of ACE.