The influence of brood chickens by-products processing with probiotic culture starter on change of their functional and technological parameters

By-products are the potential source of animal protein obtained from brood chickens and egg-laying hens. Certain by-products like gizzards and combs are quite tough and possess low nutritional and biological value due to their high content of connective tissue. Biotechnological processing improves the quality parameters of collagen-containing by-products. In this article a probiotic starter culture of propionic acid bacteria, which have high proteolytic activity, was used to treat the gizzards and combs of brood chickens. Before processing of by-products with starter culture, physical and chemical parameters and the yield of by-products in relation to poultry live weight were analyzed and recorded. 5%, 10% and 15% starter culture were added to the tested samples of chopped by-products, the samples were kept at a temperature of 30 °C, and every 4 hours the following functional and technological parameters were monitored: moisture binding capacity, water holding capacity (MBC and WHC) and yield of the product after heat treatment. The results proved that increase of starter culture amount and longer exposure of by-products to hydrolysis led to decrease of functional and technological parameters values, but for the combs those parameters remained at a sufficiently high level compared to the gizzards, as the gizzards were exposed to more intense hydrolysis than combs. The decrease in the pH value correlated with the dynamics of MBC and WHC changes; and dynamics of the product yield after the heat treatment. Also the stained histological preparations were studied in order to assess the influence of biotechnological processing on by-products microstructure, where significant differences were found in the morphological structure of muscle and collagen fibers of hydrolysates of combs and gizzards exposed to action of bacterial concentrate. The results of rheological studies showed that hydrolyzed chicken combs differed from gizzards; the combs were denser and featured more elastic structure due to a lower degree of hydrolysis by bacterial enzymes. In general, the properties of collagen-containing by-products (muscular gizzards and combs) change significantly after being exposed to enzymes of propionic acid bacteria.