Effects of salting processes and time on the chemical composition, textural properties, and microstructure of cooked duck egg

Chemical composition, textural properties, and microstructure of cooked duck egg salted by 2 methods (coating and immersing) were determined during 4 wk of salting. As the salting time increased, moisture content increased and salt content decreased for both cooked salted egg white and yolk. Oil exudation of cooked yolk and expressible water content of cooked egg white obtained from both salting methods increased as salting proceeded (P < 0.05). After cooking, oil exudation accompanied by the solubilized pigments, especially at the outer layer of yolk, was obtained. At week 3 of salting, egg yolk from coating method had the higher egg exudation than that from immersing method. As the salting times increased, the lower hardness, springiness, gumminess, chewiness, and resilience with higher adhesiveness and cohesiveness were generally found in cooked salted egg white (P < 0.05), irrespective of salting methods. Conversely, the hardness of cooked yolk increased continuously and reached the maximum at week 2 and 2 to 3 for immersing and coating method (P < 0.05), respectively. Confocal laser scanning micrographs revealed the smaller yolk granules with more release of free lipid in salted egg after heating, compared with the fresh counterpart. As visualized by scanning electron microscope, gel of cooked salted egg white was coagulum type with larger voids. Salting methods determined oil exudation in egg yolk and texture profile of egg white gel after cooking; however, those attributes were also governed by the salting time. PRACTICAL APPLICATION: Salted duck egg can be made by 2 methods (coating and immersing) affecting the characteristic of salted egg white and yolk after cooking. Desirable cooked salted egg having the red yolk with hardness and high oil exudation could be obtained when salting was carried out for 3 and 4 wk for immersing and coating method, respectively.     

蛋清蛋白肽体外抗氧化作用模式的研究

目的 研究蛋清蛋白肽抗氧化作用模式。方法 利用超滤技术分离蛋清蛋白木瓜蛋白酶酶解产物; 采用Fenton体系、邻苯三酚自氧化体系和亚油酸自氧化体系分别测定超滤各组分清除羟自由基、超氧阴离子及抑制脂质过氧化的能力, 同时测定各组分对二苯代苦味肼基自由基清除能力(DPPH自由基)、还原能力及对猪胎儿成纤维细胞(porcine embryonic fibroblast, PEF)过氧化损伤的保护作用。结果 超滤各组分中分子量小于3 kDa组分(蛋清蛋白酶解产物-Ⅲ, egg white protein hydrolysate, EWPH-Ⅲ)占蛋清蛋白酶解产物(EWPHs)总量的50.06%。EWPH的抗氧化活性随分子量的降低而增强(P<0.05), 其中EWPH-Ⅲ在浓度为5 mg/mL时, 对羟自由基、超氧阴离子、DPPH自由基的清除率分别为52.86%、35.05%和78.74%, 对亚油酸氧化的抑制率为74.57%。在浓度为2.5 mg/mL时, PEF细胞存活率达到70.06%。结论 蛋清蛋白肽具有较强的抗氧化活性且分子量越小, 抗氧化活性越强, 可以作为氢供体、自由基稳定剂和金属离子螯合剂来抑制过氧化作用。     

腌制方法对鸭蛋黄成分变化及品质影响

研究了鸭蛋在草木灰包裹法和盐水浸泡法腌制过程中,水分含量、盐分含量、R值与Q值,蛋黄总脂肪、可溶性蛋白质和巯基含量的变化以及成熟(7周)后两者蛋黄的感官品质。7周内,随腌制时间的延长,浸泡法鸭蛋黄水分含量明显低于包裹法鸭蛋黄,盐分含量却高于包裹法;蛋清R值高于蛋黄,灰蛋的R值、Q值都低于盐水蛋。第7周,灰蛋和盐水蛋的Q值上升为0.88和0.90;脂肪占湿重的含量上升至48.45%和50.67%,而腌制期总脂肪量是没有变化的;可溶性蛋白质含量增加至6.75%和6.08%;表面巯基和游离巯基下降至0.31、0.28mmol/g蛋黄和1.68、1.34mmol/g蛋黄。灰蛋蛋黄在形态、滋味和气味方面明显优于盐水蛋,感官评分分别为88.9和78.65。     

Comparative study on physicochemical and functional properties of egg powders from Japanese quail and white Leghorn chicken

Physicochemical and functional properties of freeze-dried egg powders (egg white, egg yolk, and whole egg) from Japanese quail and white Leghorn chicken were studied comparatively. All egg powders had protein content in the range of 91.13–97.03 g/100 g powder. The quail egg powder had higher mineral and essential amino acid contents, but lower fat content as compared to chicken egg powders (P < 0.05). Moreover, egg white powder from both quail and chicken presented higher total amino acids content than corresponding whole egg and egg yolk powders, respectively. Fourier transform infrared spectroscopic study revealed that β-sheet is the major secondary structure of all egg powders. Based on differential scanning calorimetry analysis, quail egg powders showed slightly lower denaturation temperatures than corresponding chicken egg powders (P < 0.05). Sodium dodecyl sulfate–polyacrylamide gel electrophoresis study showed the slight difference in protein patterns of corresponding quail and chicken egg powders. The quail egg powders presented higher protein solubility than corresponding chicken egg powders at all pH tested. Furthermore, quail egg powders exhibited higher emulsion activity index and emulsion stability index with higher foam expansion and stability than the corresponding chicken egg powders. Therefore, Japanese quail egg powders could be used as an alternative to white Leghorn chicken egg in the preparation of foods and diets that require high protein content with positive health benefits.     

Effect of salting processes on chemical composition,textural properties and microstructure of duck egg

BACKGROUND: Salted eggs have been produced in Thailand and consumed nationwide. Salted egg can be made by brining eggs in saturated saline or by coating the egg with soil paste mixed with salt. The achievement of salting is generally indicated by the textural development of egg yolk. Yolk property is therefore a prime factor governing consumer acceptability and market demand. The objective of this study was to determine chemical composition, textural properties and microstructure of duck egg obtained from the coating and immersing methods at different salting times. RESULTS: Decreases in moisture content with coincidental increases in salt content in both egg white and yolk were observed during salting, regardless of salting process. However, no difference in salt content was noticeable in yolks (P > 0.05). The paste coating method tended to yield greater oil exudation of egg yolk than the immersing method. Maximum transition temperature (T_max) of egg proteins and thiobarbituric acid‐reactive substance (TBARS) value in yolk increased with increasing salting time. A similar hardening ratio of yolk was observed in both processes. Higher hardness and adhesiveness were found in yolk with the paste coating method, whereas greater fracturability, springiness, gumminess and chewiness were observed with the immersing method. Nevertheless, both processes rendered the yolk with similar cohesiveness. Yolk granules were aligned closely when salting proceeded, irrespective of salting process. CONCLUSION: Dehydration and release of lipids in egg yolk increased with increasing salting time and were more pronounced with the paste coating method. Therefore salting processes affected the properties of salted eggs. Copyright © 2009 Society of Chemical Industry     

皮蛋加工腌制粉的研究

本研究选用两批共10组配方的皮蛋粉,通过对各组加水搅拌料泥后部分性质的比较,以及选用新鲜完好的鸭蛋为原料,滚蛋、密封保存,通过对其定期抽样检测及皮蛋成品的质量检测,确认第二批第四组配方较为理想,用该粉剂做成的皮蛋成品香、味俱佳,碱Cu、Zn的含量均符合国家标准,是一种方便城乡居民的产品.     

鸭卵清溶菌酶的分离纯化及性质

通过硫酸铵的分级沉淀、CM-Sepharose阳离子交换层析、Superdex-200凝胶过滤层析等步骤,从鸭卵清中获得电泳纯的溶菌酶,该酶的比活力达到33687.26U/mg,纯化倍数为109.44,回收率为28.00%。测得该酶分子质量约为14.82kD,对溶壁微球菌的最适反应温度为50℃,最适pH值为7,且在50℃以下及pH5～9有较好的稳定性,同时在最适条件下测得其Km值为0.0864mg/mL。Fe2+、Mg2+、Mn2+等金属离子对该酶有较强的抑制作用,而Zn2+、Cu2+、Co2+对该酶有一定的激活作用。     

腐败蛋黄卵磷脂的提取

对腐败蛋黄卵磷脂的提取工艺进行初步探讨。结果表明,用95%乙醇提取3次获得约含18.5%卵磷脂的粗品卵磷脂,使用5%ZnCl2纯化粗卵磷脂后的回收率约为85.4%,含量达96.8%。薄层色谱分析结果显示自制的卵磷脂与卵磷脂样品Rf值一致。     

挤压对蛋黄粉性质的影响

采用双螺杆挤压膨化机对蛋黄粉进行加工,研究挤压工艺对蛋黄粉挤压产品色泽、可溶性蛋白质和氨基酸的影响。结果显示,提高进料水分,降低机筒温度,有利于降低挤压蛋黄粉的色差值,并能减少可溶性蛋白质和氨基酸的损失;螺杆转速提高,挤压蛋黄粉的色差值呈总体降低趋势,而可溶性蛋白和氨基酸的含量呈先提高后降低的趋势。     

蛋黄卵磷脂研究概况

卵磷脂是一种重要的具有营养与保健功能的天然物质。目前国内外关于卵磷脂的基础与应用研究很多,但绝大部分都是针对于大豆卵磷脂。蛋黄卵磷脂的研究起步较晚,但由于其含量高,且蛋黄卵磷脂具有优于大豆卵磷脂的一些特性,因此目前关于蛋黄卵磷脂的功能特性以及应用开发日益受到人们的关注。我国是禽蛋大国,对蛋黄卵磷脂的研究方兴未艾。本文对蛋黄卵磷脂的分离纯化、检测方法、基础性质、功能性以及应用研究现状分别作了详细的阐述,并提出了蛋黄卵磷脂今后的研究发展方向。