Microbial fermentation of poultry by-products

The aim of this research is to analyze the effect of microbial fermentation of poultry by-products on the accumulation of protein hydrolysis products and changes in the microstructure of hydrolysates. The objects of the study were the gizzards of broilers and hens of the parent flock, which were subjected to microbial fermentation with bacterial concentrates of propionic acid bacteria and bifidobacteria. Fermentation was carried out at temperatures of 30, 35 and 40 °C for 16 hours. To analyze the degree of hydrolysis, the content of amine nitrogen was determined every 4 hours of fermentation. It was noted that under the action of microbial enzymes, a deeper hydrolysis of the protein molecule occurs with an intensive accumulation of amine nitrogen. At the same time, the highest accumulation of amine nitrogen is observed during microbial fermentation of gizzards by propionic acid bacteria at a temperature of 30 °C, and by bifidobacteria at a temperature of 40 °C. In addition, the degree of hydrolysis has been assessed by the accumulation of free amino acids. An increase in the concentration of free amino acids in the control and experimental samples of hydrolysates after 16 hours of fermentation was found. In the hydrolysates of gizzards fermented with propionic acid bacteria and bifidobacteria a significant accumulation of the essential amino acids was observed. The content of both essential and nonessential amino acids in the hydrolysates of broiler chicken by-products was several times higher than in hen’s by-products. The study of the microstructure of hydrolysates using scanning electron microscopy has shown that under the action of microorganisms there have been significant changes in the structure of muscle and collagen fibers, their dissociation into numerous thin fibrils and the formation of a reticular structure in combination with globular proteins and mineral components of serum. Samples treated with bacterial enzymes had a more open microstructure and greater porosity. As a result of the study performed, it was established that the microbial fermentation promotes a deep hydrolysis of proteins in the by-products of chickens and hens. When the temperature conditions of fermentation are suitable for each type of bacteria, hydrolysis occurs more intensively.