Enzymatic Hydrolysis Characteristics Of Duck Bone And Duck Flavor Preparation Of Its Hydrolysate

Duck bone, which is one of the staple by-products of duck meat processing, enjoys rich andhigh quality protein and minerals. Enzymatic hydrolysis can improve the protein extraction rate.Further development and product development using Enzymatic hydrolysis and Maillardenhancing arome reaction techniques in this thesis means practical significance for recycling duckbone resources and the continued development of the duck meat processing industry.In this thesis, the basic nutrients and composition characteristic of protein had been analyzed,on this basis, the nutritional characteristics and the hydrophobic value of protein had also beenstudied; Four proteases(Papain, Pancreatin, Protamex, Flavorzyme) were employed to hydrolyzeduck bone protein to study the variation in the process of single enzymatic hydrolysis anddual-enzyma complex enzymatic hydrolysis, and chose different enzymatic hydrolysates accordingto the product needs. In addition, the optimum conditions of the controlled duck fat had beenstudied, and the volatile arome components had been analysised; Finally, Maillard enhancingarome reaction model were established with duck bone protease hydrolyzates to prepare duckflavor of fat oxidation type. The main results were as follows:(1)The composition of duck bone showed that it had high content of protein up to29.19%andhigh content of essential amino acids、flavor amino acids and sulfur-containing amino acids,respectively43%、25%、4%, which were flavor precursor for duck flavor. The amino acid scorepoints of all essential amino acids had exceed the rating of the AAS standard mode, The aminoacid score points of Ile、Leu、Lys、Phe+Tyr、Thr had exceed or closed to the rating of CS standardmode. The hydrophobic value of duck bone protein was low as1082.27Cal/mol.(2)During duck bone protein treated by the four proteases, the content of soluble nitrogen(SN)and amino nitrogen(AN) of the enzymatic hydrolysates had been increased fast as hydrolysis timeprolonged, and solw down in4hours; the content of peptidyl nitrogen(PN) increased first andreached to a maximum value, then declining slowly; After12hours, there were littlemacromolecular peptides segment and many low molecular weight peptides in the enzymatichydrolysates; There were some differences in the totle content of free amino acids(FAA). Therewere the most amount of free amino acids、flavor amino acids and sulfur-containing amino acids inthe enzymatic hydrolysates treated by Flavorzyme. Therefore, the regular of release of free aminoacids had been studied in the enzymatic process treated by Flavorzyme. It was found that all aminoacids released at a different speed. After12hours, The free amino acids content reached to89.1 mg/100mL（178.2mg/g protein）, which is3.04times of that enzymatic hydrolysates treated for2hours, flavor amino acids content increased and sulfur-containing amino acids was almost7%.(3) Papain、Panctreatin and Protamex were selected to mixed with Flavorzyme respectively tohydrolysis duck bone protein, the result suggested that the variation of SN、AN and PN contentwere the same as that of the single enzymatic hydrolysis process. The content of SN and PN in theenzymatic hydrolysates treated by Protamex and Flavorzyme were significantly lower than that ofthe other two composite enzymes, and AN content was higher than that of the other compositeenzymes. Therefore, the regular of release of free amino acids had been studied in the enzymaticprocess treated by Protamex and Flavorzyme. Each amino acid content increased as hydrolysistime prolonged, which is42.6mg/100mL（85.2mg/g protein）after2hours and89.3mg/100mL（178.6mg/g protein）after12hours. Therefore, the enzymatic hydrolysates treated by Protamexand Flavorzyme were employed to prepare the duck flavor.(4) The optimum oxidizing conditions of duck fat was: oxidizing temperature120℃,oxidizing time4hours. In this condition, the POV value was22.30meq/kg, P-AV value was7.04,AV value was0.93mgKOH/g, the duck fat had a strong aroma and slightly fried flavor. The volatilearoma components of duck fat before and after oxidation by SPME-GC-MS were analyzed,compared to duck fat not oxidized, duck fat oxidized was detected32flavor compounds andrelative content was72.32%, type and content of which were increased, including13kinds ofaldehydes and the relative content was42.29%. The relative content of hexanel was the highest andreached to29.40%. In addition, hydrocarbons、furans、alcohols、carboxylic acids and a variety offlavor compounds were also detected.(5)Hydrolysate treated by Protamex and Flavorzyme for8hours was selected as the main rawmaterial by Maillard thermal reaction and brief description and emotional test method to prepareduck flavor. On the basis of single factor test, selected thiamine、the ratio of reducing sugars、oxidizing duck fat and reaction time which had large impact on the flavor of product, with fourfactors and three levers of orthogonal experiment to optimize the raw materials and processconditions of Maillard reaction: duck bone hydrolysis products50mL, HVP10g, L-cysteine0.5g,L-alanine0.5g, glucose:xylose=1:1, total2g, oxidized duck fat2g, thiamine0.2g, salt0.3g;temperater120℃, time30min. The duck flavor prepared in the optimized formulations andconditions was concentrated, rich flavor, coke flavor and fat flavor.42kinds of volatilecomponents were detected by SPME-GC-MS, including13kinds of aldehydes(37.35%)、9kinds ofketones(8.75%)、8kinds of alcohols(18%)、2kinds of hydrocarbons(1.35%)、2kinds offurans(2.59%)、4kinds of carboxylic acids(10.73%)、4kinds of pyrazine and thiazole(1.86%). Itshowed that aldehydes、ketones and alcohols were the major volatile compounds and accounted for64.10%in all volatile compounds.