| The law of hydrolysis and the physicochemical and functionalproperties of desalted duck egg white hydrolysates generated withalkaline, hydrochloric acid, and proteases respectively was investigated.The results achieved were as the follows:Alkaline and Hydrochloric Hydrolysis:1. The degree of hydrolysis (DH) of desalted duck egg white increasedwith the increase of the hydrolysis temperature, time andconcentration of NaOH and HCl respectively2. In the case of alkaline hydrolysis or hydrochloric hydrolysis, solublenitrogen increased when DH of the hydrolysate getting was higher.Hhydrolysed by alkaline, the soluble nitrogen of hydrolysate did notincrease obviously after the DH exceed 2l .04%,and hydrolysed byhydrochloric, the corresponding DH is 2l%.3. The thermal stability of the hydrolysates also increased obviouslywhen the DH was getting higher The thermal stability index canreach 9mg/ml and 7mg/ml in the case of alkaline hydrolysis andhydrochloric hydrolysis respectively.4. After limited hydrolyzed by alkaline, the protein hydrolysates'emulsion stability increased, and at DH 4. l4%,it reach its biggestpoint. If the DH rose higher, the emulsion stability decreasedinsteadly. But the hydrochloric hydrolysates' emulsion stability islower than that of duck egg white.5. The result of the SDS-PAGE showed that the protein molecular hadgotten smaller. Most big molecular protein had been discoveredwhen the DH exceed 8%.6. The duck egg white turn pistachio with some white deposit whenthe duck egg white was hydrolyzed by NaOH. When temperaturereached l00℃the color turn brownish red because of Maillardreaction. Free ammonia gave off when the duck egg white washydrolyzed by NaOH. In hydrochloric hydrolysis, there was little red in the duck egg white. when the temperature got l00℃ the colourturn brown. After neutralized, both alkakline hydrolysate andhydrochloric hydrolysate have no bitterness.7. Treatment of food protein with NaOH can cause amino acyl residuesracemization and formation of isopeptide,such as Lysinoalaine(LAL).While in hydrochloric hydrolysis, chloropropanol was produced.thcse new resultant can do harm to man.One Enzyme Hydrolysis1. At PH8.0, 37℃, 2000u/g, the Pancreatin was working to its best. Inthis condition, the DH can reach l7.5% in 5 hours. The besthydrolytic condition of Flavourzyme is l60LAPU/G, PH 7.5, 50℃.For As l .398 protease, the best condition is PH7.3, 45℃, 6000u/g.2. Between PH2 and PHl0, the soluble nitrogen of the hydrolysate ismore stable than desalted duck egg white. When the DH reachedl5.2%, the pancreatin hydrolysate's soluble nitrogen can reach7.8mg/ml, and. As1 .398 protease hydrolysate reach 8.72mg/ml atpH2. The soluble nitrogen of Flavourcyme hydrolysate is 8.3mg/mlat pH2. While the soluble nitrogen of duck egg white is 3. l7 at thesame condition.3. At pH7, desalted duck egg white gels when it is heated by 85℃ for5 min. But the enzymatic hydrolysates keep liquid in the samecondition. It indicate that the thermal stability of the enrymatichydrolysates is better than desalted duck egg white.4. Limited hydrolyzed by protease, the protein hydrolysates emulsionstability increased. For pancreatin hydrolysate, when the DH reachabout 9%, emulsion stability can get highest point. But the emulsionstability of Flavourryme hydrolysate didn't increase remarkably.While the emulsion stability of As1 .398 protease hydrolysatedecreased observably comparing with the duck egg white.8. Hydrolyzed by protease, the big protein molecule reduced. When DHwas over 20%, most polypeptides were too small to be dotected bySDS-PAGE.9. After centrifuged, the supematant ofhydrolysate was transparent.The pancreatin hydrolysate had the smell of viscera. Theflavourzyme hydrolysate smell nice. All kinds ofhydrolysate tastedelicious without bittemess.enzymatic hydrolysis by two kinds of proteasesl. The degree ofhydrolysis can b... |
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