脱盐咸鸭蛋蛋清的水解规律研究

【作者】 张英君；

【导师】 陈有亮；

【作者基本信息】 浙江大学 ， 食品科学， 2001， 硕士

【摘要】 本试验深入研究了咸鸭蛋蛋清的碱水解、酸水解、单酶水解、双酶水 解和发酵水解的规律及其相应水解产物的理化特性，从而为利用咸鸭蛋蛋 清生产生物活性多肽提供理论基础。主要试验结果如下： 一、碱、酸水解 (1）咸鸭蛋蛋清的水解度随着 NaOH（或盐酸）浓度的增大、反应温度的 升高和水解时间的延长而增大。 （2）通过碱水解或酸水解，蛋清水解物的水溶性得到改善，受溶液PH 的影响减小。当水解度达到21％时，碱水解物水溶性指数可达到 10 mg/ml以上，酸水解物水溶性指数可达到8mg/ml以上。水解度 再增加时，水溶性指数有少量的增加。 （3）碱、酸水解物的热稳定性显著提高。水解度在21％以上的水解物热 稳定性指数分别达到9 mg/ml和 7mg加 以上。水解度相同时，碱 水解物比酸水解物的热稳定性指数要高。 (4）经碱水解的咸鸭蛋蛋清的乳化稳定性有较大增加，当水解度达 4．14％时，乳化稳定性最好，随着水解度的进一步增加，乳化稳定 性降低。经过酸处理的咸鸭蛋蛋清的乳化性降低。 （5）SDS－PAGE电泳图谱显示：经过碱、酸处理后的蛋清，小分子量的 成分增加，大分子蛋白质减少。 （6）50℃时的碱水解液呈浅黄绿色，有白色沉淀。75℃时的碱水解液呈 黄绿色，反应液底部出现白色絮状沉淀或悬浮物。100℃时的水解 液呈黄褐色，有白色沉淀。反应过程中有氨气放出，且随水解度的升高而增多。酸水解液随着盐酸浓度和温度的增加，产物的颜色可 变为淡红、浅红、浅褐色或深棕褐色。碱、酸水解液呈鲜咸味，略 有异味，无苦味。 (7）碱处理蛋白质引起氨基酸变旋和赖丙复合物的生成。由于D-型氨 基酸不能被生物利用以及赖丙复合物有潜在的毒害作用，因此碱处 理蛋白质的安全性受到置疑。酸水解蛋白质中常含有因脂肪分解而 产生的致癌物质——氯丙醇而应在食品中慎用。 二、单酶水解 (1）从水解度、水解时间和用酶水平的角度考虑，各种蛋白酶水解蛋清 的最佳条件如下： 底物：蛋清（蛋白质浓度8．8％）经过胶体磨处理，100℃加热15 分钟变性。胰酶水平2000u／g、PH8.0、 温度37℃、水解5小时可 以得到水解度为 17．9％的水解液；风味酶水平 160 LAPU／G、PH7．5、 温度 50℃、水解 7小时可以得到水解度为 12．7％的水解液；As1，398 蛋白酶水平 6000u／g、PH7．3、温度 45 ℃、水解 6小时可以得到水 解度为 19．4％的水解液。 （2）在 PH2-10 之间，脱盐鸭蛋蛋清蛋白酶水解物的可溶性氮含量不受 水解度影响。在 PH4时，水解度为 15．2％的胰酶水解物水溶性指数 可达7．8mg/ml：水解度为10％的风味酶水解物水溶性指数达到8．3 mg／ml；水解度为15％的As1．398蛋白酶水解物水溶性指数达到8．72 mg／ml。而脱盐鸭蛋蛋清水溶性指数为 3．17 mg／ml。 (3）在PH4，脱盐鸭蛋蛋清85℃受热5分钟发生凝固，而酶水解物不 产生凝胶，水解度为 15.2％的胰酶水解物热稳定性指数为 8．5mg／ml，水解度为 10％的风味酶水解物热稳定性指数为9.21mg/ml，水解度为15％的As1．398蛋白酶水解物热稳定性指数 为9.1。热稳定性随水解度提高而增强。 （4）脱盐鸭蛋蛋清经过有限地水解，可以增加乳化稳定性。经过胰酶水 解，水解度为9．3％时的水解物乳化稳定性指数在PH10达到最大 值，57mm。用风味酶水解所得产物乳化稳定性增加不大。而用 As1．398蛋白酶水解得到的水解物乳化稳定性有所减小。 （5）脱盐鸭蛋蛋清经过酶水解后，当水解度达到 15％－20％以上时，绝大 部分的大分子蛋白质被水解成分子较小的多肽。 (6)脱盐鸭蛋蛋清经过酶水解、离心后的上清液透明：胰酶水解物略带 动物脏器的气味，风味酶水解物风味芳香宜人；各种水解物口感涩 鲜，强度随水解度增加而增大，没有明显苦味。 三、双酶水解结论 (1）经过双酶水解，又有一部分变性的大分子蛋白质的肽链断裂，水解 度进一步增大，产生大量的短肽甚至是氨基酸，使水解度可以达到 81％。 (2）水解度的提高可使可溶性氮含量提高，水?更多还原

【Abstract】 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更多还原