| dc.description.abstract | Increasing demand for meat products as a result of population growth has resulted in the production of more and more chicken rest raw material. This thesis aims to recover fat and protein from chicken rest raw materials using a two-stage extraction method for chicken viscera and mixtures. Experiments were carried out to analyse the quality of lipids and proteins after extraction by the following measurements, including dry matter, ash, fat and protein content, Peroxide value (PV), TBARS, amount of free fatty acids, degree of hydrolysis (DH) as well as amount and composition of free amino acid.
The first stage involved the separation of fat by thermal processing (water bath) at a variety of temperatures (45, 40, 55, 60, 65°C), while the second stage involved the recovery of protein from the remaining material by enzymatic hydrolysis. According to Bligh and Dyer, the fat content of the raw materials was 21.77% and 19.8% in chicken viscera and bone mixtures, respectively, and the fat yield was 9% after separation, indicating that the water bath temperature had no effect on the fat yield. According to the results of the study, the peroxide value of lipid isolated from the viscera ranged between 30.26 meq O2/kg at 45°C and 4.22 meq O2/kg oil at 65°C. The peroxide value (PV) in the fat extracted from the bone mixture ranged between 6.27 meq O2/kg and 2.80 meq O2/kg. With increasing temperature, the PV in raw chicken material decreases. The TBARS values of secondary products in the fat extracted from the viscera showing the similar trend with bone mixture sample, which is from 0.22 µmol/g oil to 0.06 µmol/g oil. While chicken bone mixture TBAR values decreased with increasing temperature, from 0.086 µmol/g oil to 0.023 µmol/g oil. Free fatty acid content of the raw material from the viscera and bone mixture was much higher than that of the separated fat, but did not change significantly between 45°C and 65°C, at around 7% and 0.7%, respectively. According to the results, thermal processing affects free fatty acid %, but temperature has no influence on this content. There is inevitable lipid oxidation and the reduction of free fatty acid content derived from the extraction process, but the lowest level occurs at 65°C.
A combination of endogenous and exogenous enzymes, Endocut-02L, produced the most effective extraction results for proteins in chicken vescera samples with 19.91% water-soluble protein at 55°C and 20.15% at 60°C. At 55°C and 60°C, the endogenous enzyme and the exogenous enzyme Endocut-02L produced the second highest hydrolysis. With the endogenous enzyme and Endocut-02L combined, the hydrolysates of the samples of the bone mixture had the highest protein content of 29.85% when dissolved at 50°C. In contrast, the other groups did not perform as well. It was also found that there was no correlation between the hydrolyzed protein content and the percentage of wet weight of the hydrolysed phase. The degree of hydrolysis was determined in the group at 55°C and utilizing multiple enzyme treatments. A multiple enzyme extraction at 55°C resulted in a maximum hydrolysis of 24.79% of the viscera sample. For the bone mixture sample, the Endocut-02L was more appropriate with 17.05%. In addition, endogenous and exogenous enzymes had no effect on the composition of amino acids in the protein hydrolysate in chicken RRM. All groups obtain Asp，Glu，Asn，His，Ser，Gln，Gly/Arg，Thr，Ala，Tyr，Aba，Met，Val，Phe，Ile，Leu and Lys these 17 amnio acids. And it was found that different temperatures were used to obtain the highest content from the viscera and bone mixture samples. The highest content of amino acids in the bone mixture is obtained by endogenous enzymes combined with Endocut-02L at 45°C with 845.52 µmol/l. The endogenous enzyme performs better in viscera samples at 55 °C with 1544.92 µmol/l. | |