Enzymatic Hydrolysis Of Duck Bone And Primary Application Of Its Hydrolysate

Duck bone is one of the most important by-products of poultry-processing but has a very low utilization rate. It is important for improving this situation and facilitating sustainable development of poultry-processing industry by using enzymolysis technology and Maillard reaction techniques. This study includes several aspects as the following: analyzing the ingredients of duck bone and evaluating the nutrition value of it's protein; research on the conditions of hydrolysis by single or multienzymatic protease; analysis of the hydrolysates of duck bone hydrolyzed under the optimum conditions; preparation of duck flavor by Maillard reaction use the duck bone hydrolysates; opitimization of the conditions of Maillard reaction and analyzing the volatile compouns of duck flavor by SPME-GC-MS.The protein and the necessary amino acid content was high in duck bone. The amino acid score of methionine & cystine and lysine were higher than these in the model of FAO/WHO or whole eggs. However, the protein of duck bone is an imperfect protein because it has a low essential amino acid index (EAAI). Duck bone has a high tasty amino acids, and what's more, had a good taste when been heated. So it has a potential to employ flavoring base.Four protease (neutrase, flavourzyme, papain and alkaline protease) were used to hydrolyze duck bone. The hydrolysis condition were optimized by the degree of hydrolysate (DH) and SN-TCA index based on the research of each single factor and then step-wise multienzymatic protease hydrolysis of duck bone was studied. The results show that it was better hydrolyzed by multienzyme than single protease, the DH and SN-TCA index were increased. Different adding order of the protease lead to different hydrolysis effect and used papain hydrolysed duck bone following alkaline protease was the best, the degree of hydrolysis the SN-TCA index under this condition reached 34.71% and 81.78%, respectively. The composition changed much after the hydrolysis. The content of the necessary amino acid and tasty amino acids increased much, and the sulfur amino acids decreased in the hydrolysate compared to the raw material of duck bone. The peptide molecular weight was analyzed by HPLC and the results shows that the hydrolysate contents 7 peptides of different molecular weight at least and the relative molecular weight were lower 8000D, which contained 31.35% peptides of the relative molecular weight lower 1000D. It indicated that the compact structure of duck bone protein was destroyed and the aim of hydrolysis was reached, and what's more, the content of the necessary amino acid were increased which shows that the nutritive value of duck bone protein was improved. The conditions for Maillard reaction to produce duck flavorings optimized by the Friedman methodology based on the basic prescription and the hydrolysates of duck bone as the main composition. The optimum conditions were as the follows: The hydrolysates of duck bone of 10g, HVP of 2g, cysteine hydrochloride of 0.34g, alanine of 0.66g, glucose of 1.0g, duck fat of 0.2g, reacted at 125℃, pH5.5 for 50min.The duck flavor has a good duck characteristic flavor when prepared on the base of duck bone hydrolysates. The GC-MS results of duck flavor showed that, 62 compounds were detected, 13 of hydrocarbon, 18 of heterocyclyclic, 7 of aldehydes and ketones, 6 of alcohols, 8 of sulfur compounds and other volatile compouns; hydrocarbon, heterocyclyclic, aldehydes and ketones, alcohols and sulfur compounds accounted for 79.81% in all volatile compouns.