In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups.

In order to exploit industrial discards, protein enzymatic hydrolysis is a currently popular methodology for obtaining bioactive peptides. However, once released, most promising peptides have to be selected from the mixture. In this work, the suitability of pepsin (EC 3.4.23.1) to hydrolyse serum albumin in order to obtain bioactive peptides was assessed. Then, a suitable process to obtain best separation of bioactive peptides was evaluated, using polyethersulfone membranes at different pH values. Serum albumin was easily hydrolysed by pepsin, reaching a DH value of the 65.64 ± 1.57% of the maximum possible. A 23.25% of the identified peptides possessed high bioactivity scores (greater than 0.5), and one of them had reported bioactivity (LLL). Charge mechanisms always predominated over the sieve effect, and best transmission was accomplished at pH values close to the peptides isoelectric points. Basic and neutral peptides with the highest scores were always the most transmitted. Membrane material had greater influence than NMWCO in determining peptide transmission. In order to obtain purified fractions rich in peptides with high bioactivity scores from serum albumin, polyethersulfone membranes (applicable to industrial scale) of 5 kDa MWCO should be used at basic pH values after pepsin digestion.

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