Features of the Amino Acid Composition of Gelatins from Organs and Tissues of Farm Animals (A Review)

Gelatins are formed during processing of animal connective tissues (primarily collagens) and, from a biochemical point of view, are polypeptide products. In the case of the commercial gelatins the majority, on 52.5%, is made from the bovine skin and bones, on 46.0%—from porcine skin, and only 1.5%—from other animal tissues. At the beginning of the 21st century, the bulk of commercial gelatins are used in food industry, about a third in the medical sector, and only about 6% in technical or other industrial applications. Currently, trends toward a healthy lifestyle have intensified, which, along with the religious and cultural traditions of many countries, encourages scientists to look for gelatin sources not related to mammals but close to them in physicochemical and functional characteristics. Therefore, recently a tendency has emerged for a decline in the huge production of gelatins from mammals (cattle and pigs), although not significant compared with the relative increase in the production of gelatins from by-products and waste from industrial poultry farming. Moreover, over the past decades, global poultry meat production has increased by more than a third. It was shown that bovine and porcine skin gelatins have optimal amino acid (AA) compositions for their applications. Of course, the AA compositions of porcine and bovine gelatins obtained under different technological conditions may vary significantly. However, in general, these differences are not critical and, therefore, sometimes gelatins are obtained from mixed animal waste. Recently, in Russia, a composition of protein ingredients from porcine and bovine skin hydrolysates with the addition of dried blood plasma has been developed, which had a much better AA composition than traditional gelatins, and this suggested increased biological and nutritional values of the developed product. In addition, various authors found that some specific peptides improved a number of parameters and biological properties of gelatins from mixed animal waste. Thus, new compositions with an optimal AA composition and improved nutritional and functional properties are being actively developed on the basis of known gelatins. The present review provides a detailed description of the main studies on the AA composition of gelatins and its relationship with the key biochemical and technological indicators of gelatin-based materials.