Characteristics of food collagen hydrate obtained from pikeperch skin by FTIR spectroscopy

Abstract

Authors developed a method for processing fish skin, which makes it possible to obtain a food hydrate. Method consists of skin preliminary cleaning from cuts in muscle tissue and the subsequent separation of fish scales. The resulting pikeperch skin was mixed in a container with water, food salt NaCl and soda NaHCO₃ taken respectively in a mass ratio of 100:400:5:1, kept for 40 minutes and washed with water. The cleaned skin was mixed with apple juice in a mass ratio of 1:10 and kept at 4 deg C for 6 days. During exposure (144 hours) in the juice, the weight of the skin increased by 4.47 times compared to its initial weight, while there was a decrease in the acidity of the juice from pH 3.54 to 3.70. Swollen after 48 hours of aging in juice, the skin was easily torn (without effort) and rubbed with fingers. To characterize the original skin and juice, as well as samples obtained during their joint exposure and taken every 24 hours during the entire process (6 days), the FT-IR spectroscopy method was used, which showed the presence of functional groups of collagens (amide A, B, I, II and III) in prototypes. The difference in wavenumbers between amides I and II in skin samples kept in juice was less than 100 cm^-1, which indicates the preservation of the triple helical structure of collagen. The resulting hydrate from fish skin (with the preservation of the native structure of collagen) can be recommended as an independent product, or as an additive in food products.