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     

腌制对鸭蛋中油脂品质的影响

以新鲜鸭蛋为原料,采用裹蛋腌制法制备咸鸭蛋。研究了腌制过程中不同腌制时间对咸鸭蛋的蛋黄指数、水分含量,以及对蛋黄油皂化值、酸值、胆固醇含量、脂肪酸构成等指标的影响。研究结果表明,随着腌制时间的延长,鸭蛋中的水分含量逐渐降低,而蛋黄指数、蛋黄油皂化值、酸值、胆固醇含量逐渐增加。腌制后的鸭蛋中不饱和脂肪酸含量略有降低,而饱和脂肪酸和反式脂肪酸含量略有增加。总体而言,腌制并没有鸭蛋中蛋黄油的食用品质产生严重的影响。     

Changes in chemical composition,physical properties and microstructure of duck egg as influenced by salting

Changes in chemical composition, physical properties and microstructure of duck egg, during salting for up to 14 days, were determined. Duck egg consisted of 10.87% shell, 54.73% egg white and 33.94% yolk. Salting resulted in an increase in weight proportion of egg white, but a decrease in yolk proportion. Moisture contents of both egg white and yolk decreased gradually with concomitant increases in salt and ash contents as the salting time increased. Protein and lipid contents increased slightly in both interior (viscous portion) and exterior (hardened portion) egg yolk with increasing salting time. Oil exudation was observed in yolk, particularly in exterior yolk. Triacylglycerols and phospholipid, found as the major lipids in egg yolk, underwent slight changes, but no differences in protein patterns of either egg white or egg yolk were observed during salting. Hardening ratio and hardness of egg yolk increased with increasing salting time. Adhesiveness and gumminess also increased, while springiness, cohesiveness and gumminess decreased slightly when the salting time increased. Scanning electron microscopic study revealed that yolk granule was polyhedral in shape and aligned closely when the salting proceeded. Protein spheres were distributed uniformly, together with oil droplets, in salted yolk, as visualised by transmission electron microscopy. Confocal laser scanning microscope (CLSM) micrographs indicated that the greater dehydration and release of lipids took place in egg yolk during salting.     

Physicochemical Properties of Salted Pickled Yolks from Duck and Chicken Eggs

Duck egg yolk pickled by salt attained more desirable characteristics, such as orange color, oil exudate, and grittiness, than salted chicken egg yolk. Salted duck egg yolk reached a hardening ratio of 90% in 28-days; 35 days were required for the salted chicken egg yolk to achieve the same hardening. Moisture content of egg yolk affected the quantity of extracted lipid, an index of oil exudation. The moisture content of duck egg yolk was 19%, and the extracted lipid was 30%. But less than 4% lipid was extracted when moisture content was >27.5%. Under scanning electron microscopy, yolk spheres dominated the yolk structure probably responsible for the gritty texture.     

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。     

The Role of Wheat and Egg Constituents in the Formation of a Covalent and Non‐covalent Protein Network in Fresh and Cooked Egg Noodles

Noodles of constant protein content and flour‐to‐egg protein ratio were made with whole egg, egg white, or egg yolk. The optimal cooking time, water absorption, and cooking loss of salted whole egg noodles was respectively lower and higher than of egg white and egg yolk noodles. However, cooked whole egg noodles showed the best Kieffer‐rig extensibility. Differences in noodle properties were linked to protein network formation. Disulfide bonds in whole egg noodles developed faster and to a larger extent during cooking than in egg yolk noodles but slower and to a lower extent than in egg white noodles. The balance between the rate of protein cross‐linking and starch swelling determines cooked noodle properties. Ionic and hydrophobic protein interactions increase the optimum cooking time and total work in Kieffer‐rig extensibility testing of fresh noodles. Hydrogen bonds and covalent cross‐links are probably the main determinants of the extensibility of cooked noodles.     

电渗析脱盐对咸鸭蛋蛋清理化性质的影响

目的：为评估电渗析脱盐是否对鸭蛋清的功能性质和营养性有影响,研究经电渗析脱盐后鸭蛋清的部分理化性质变化。结果：脱盐后鸭蛋清的凝胶硬度在蛋白质量浓度较低时(5～8g/100mL)与鲜鸭蛋清相比无显著差异;当蛋白质量浓度为3～9g/100mL时,脱盐鸭蛋清的乳化活性及起泡性较咸鸭蛋清均有所提高,与鲜鸭蛋清相比,两者乳化活性相当,但其起泡性优于鲜鸭蛋清;SDS-PAGE、DSC及氨基酸分析表明,咸鸭蛋清脱盐前后蛋白质相对分子质量无明显变化;脱盐后的鸭蛋清与鲜鸭蛋清的氨基酸组成、热变性温度及颜色均十分接近。结论：经电渗析脱盐处理,鸭蛋清的理化性质影响不大,可作为良好的食品原辅料。     

低盐咸蛋的腌制工艺及其品质研究

提出一种两段腌制法制备低盐咸蛋的方法,分别对两段法腌制过程中咸蛋蛋白和蛋黄的水分含量、盐分含量进行实时检测,考察腌制结束时蛋黄的出油率,并且对咸蛋品质进行综合感官评定。结果表明,先使用19%盐水再换用3.5%盐水的两段法腌制工艺,咸蛋产品中蛋白盐分含量为3.64%,比传统法腌制产品蛋白盐分含量降低51.21%,口感适宜;蛋黄含盐量为0.94%,略低于传统法腌制的1.23%;蛋黄脂质渗出率为67.73%,与传统法腌制的69.22%基本相当。该腌制工艺不仅可解决传统咸蛋蛋白盐分过高、口感过咸的问题,同时也可保证蛋黄松沙出油,从而获得高品质的低盐咸蛋。     

纳米SiO2改性聚偏二氯乙烯涂膜对咸鸭蛋品质的影响

以共混法制备纳米SiO2改性聚偏二氯乙烯（polyvinylidene chloride,PVDC）基复合涂膜材料并研究其对咸鸭蛋品质变化的影响。结果表明,与未涂膜组相比,纳米SiO2/TiO2交联改性聚乙烯醇（polyvinyl alcohol,PVA）基膜材料、纳米蒙脱土（montmorillonite,MMT）改性PVA基膜材料、PVDC膜材料以及纳米SiO2改性PVDC基膜材料均能显著减少咸鸭蛋在贮藏过程中的不良品质变化（质量损失率增加、挥发性盐基氮（total volatilebase nitrogen,TVB-N）含量升高、菌落总数增加）（P＜0.05）。SiO2改性PVDC膜材料涂膜处理对咸鸭蛋质量损失率、菌落总数、TVB-N和游离脂肪酸的累积以及蛋青蛋黄中pH值变化的抑制程度显著高于其他涂膜处理组（P＜0.05）。另外,SiO2改性PVDC膜材料能显著抑制咸鸭蛋中菌落总数的增长（P＜0.05）,并维持产品的感官品质（P＜0.05）。在28 ℃、相对湿度70%条件下,与未涂膜组相比较,SiO2改性PVDC膜材料能够延长咸鸭蛋的贮藏保质期70 d（P＜0.05）,该研究结果为咸鸭蛋的保鲜运输及贮藏提供了理论依据。     

腌制条件对熟制咸鸭蛋蛋黄组织形态及组成的影响

为探索咸鸭蛋腌制条件对熟制后蛋黄组织形态及组成的影响，以期减少熟制咸鸭蛋蛋黄中的硬芯含量，通过称量法、原子火焰吸收光谱分析、凯氏定氮法、差示量热扫描分析、红外光谱分析和扫描电子显微镜观察等方法对不同腌制浓度和时间下咸蛋黄不同部位理化性质以及生熟咸蛋黄微观结构的不同进行分析。结果表明，蛋黄硬芯从鸭蛋腌制的第2周出现，随着腌制时间延长，硬芯逐渐变大，腌制完成后占蛋黄总质量的33.64%～44.80%，水分含量约为21.47%～23.49%。硬芯的Na+含量在10.66～11.47 mg/g之间。腌制完成后，蛋黄外部的游离脂肪含量约为34.79%～36.34%，与外部相比，硬芯的游离脂肪含量更低，约为17.71%～27.90%，且随着腌制液盐浓度的上升而增加。腌制后蛋黄硬芯蛋白质含量上升至30%以上，高于外部。蛋黄经加热后，硬芯部分蛋黄微粒颗粒度较小，且形成间隙较小的连续结构。盐分渗透的先后顺序导致蛋黄中不同部位在组织结构和组成成分的差异，这些差异导致了熟制后蛋黄硬芯及外部的差别，且较高的腌制时间和浓度均会加剧硬芯的形成。在15%盐浓度条件下腌制4周后，得到的成熟咸蛋黄在熟制后硬芯含量较少，...     

基于近红外光谱的腌制期咸鸭蛋理化指标无损检测

以高邮麻鸭蛋为研究对象,采集整个腌制期咸鸭蛋近红外光谱数据,对比测定其理化指标值,建立咸鸭蛋关键品质指标（蛋黄含水率、蛋黄氯化钠浓度和咸蛋黄指数）的无损快速检测模型。为尽可能削弱外部其他因素对样本光谱采集过程的影响,使用多元散射校正、归一化等预处理方法,结合竞争性自适应重加权算法（competitive adaptive reweighted sampling,CARS）、连续投影算法（successive projections algorithm,SPA）和非信息变量剔除（uninformative variables elimination,UVE）3种特征选择算法建立偏最小二乘回归模型,并在一次特征波段选取基础上提取二次特征波长,再建立偏最小二乘回归模型。结果表明,蛋黄含水率、蛋黄氯化钠浓度和咸蛋黄指数的最优波长选择方法均是二次特征波段提取法UVE+SPA,发现二次特征波段选择综合表现最优。经对比分析,蛋黄含水率、蛋黄氯化钠浓度、咸蛋黄指数最优模型结构分别是标准化-UVE+SPA-PLSR、卷积平滑-UVE+SPA-PLSR、均值中心化-UVE+SPA-PLSR,训练集相关系数...     

Effect of bilayer coating composed of polyvinyl alcohol,chitosan, and sodium alginate on salted duck eggs

The composite bilayer film based on polyvinyl alcohol, sodium alginate, and chitosan were developed in this study, and the effects of the related coating on internal-quality changes of salted duck eggs (SDEs) during storage were determined. The results showed that the overall properties of the bilayer film were better than those of monolayer films, including storage stability. Coatings could significantly (p < 0.05) reduce quality deterioration of SDEs such as water loss, oil exudation, and gritty. The bilayer coating was more effective in inhibiting the increase of egg yolk pH and total bacterial counts than monolayer coatings. After storage for 60 days, water content of bilayer coated SEDs was 19.7% higher than that of the control SDEs, oil exudation was 38% higher, and gritty texture was 27.9% higher. Moreover, bilayer coating could prolong the shelf life of SDEs to more than 60 days at 25°C and 50% relative humidity according to the results of total bacterial count experiment, while the shelf life of control SDEs was less than 45 days. This study indicated the potential application of bilayer composite coating for preservation of SDEs.     

Effect of Acetic Acid and Commercial Protease Pretreatment on Salting and Characteristics of Salted Duck Egg

Salting of duck egg pretreated with 5% acetic acid and different commercial proteases (flavourzyme, protamex, alcalase, and neutrase) was studied. After 2 weeks of salting, duck eggs soaked in 5% acetic acid for 30 min, followed by soaking in 5% (w/v) flavourzyme and neutrase had the highest hardening ratio (90.14 ± 2.43%, 90.25 ± 1.23%) with the coincidental increase in salt content in egg white and decrease in moisture content of yolk, compared with those from other treatments (p < 0.05). However, similar hardening ratio of the sample treated with alcalase was obtained to that of sample treated with either flavourzyme or neutrase (P > 0.05). After 1 week of salting, protamex showed the similar effect on hardening ratio to other proteases (p > 0.05). When eggs were pretreated with neutrase at different concentrations (0.25%, 0.5%, and 0.75%, w/v) for different times (30, 60, and 90 min), those pretreated with 0.25% (w/v) neutrase for 90 min had the shorter salting time, while soaking time did not have the impact on hardening ratio for egg treated with 0.5% and 0.75% neutrase (P > 0.05). The oil exudation of egg treated with 0.25% neutrase had the higher oil exudates than the control at week 2 and 3 of salting (P < 0.05). Treatment of neutrase had no impact on viscosity of egg white, regardless of salting time (P > 0.05). Microstructure study revealed that shell of salted egg pretreated with acetic acid had rough and porous surfaces when compared with control, whereas no changes in microstructure and FTIR spectra of shell membrane were found. Therefore, pretreatment of egg with 5% acetic acid for 30 min, followed by 0.25% neutrase for 90 min prior to salting could expedite the salting process and yielded egg yolk with hardening ratio and oil exudates, comparable to the traditionally salted egg.     

咸鸭蛋快速熟化技术研究

采用5% 醋酸浸泡鸭蛋,溶解蛋壳外膜,增加蛋壳的通透性。再采用分步式腌制工艺,既先用饱和食盐水腌制,再用10g/100mL 和15g/100mL 食盐溶液腌制。并考察腌制过程中鸭蛋的含油量、含盐量及蛋黄指数的变化。结果表明：醋酸浸泡的鸭蛋先用饱和食盐水腌制11d,再在10g/100mL 和15g/100mL 食盐溶液中腌制7d 左右,咸鸭蛋的品质不仅良好,而且腌制时间比传统工艺缩短两周左右。     

间歇超声辅助加快咸蛋腌制速度工艺优化

为加快咸蛋腌制速率,缩短腌制周期,本实验通过测定腌制过程中咸蛋含盐率、含水率、蛋黄出油率及蛋清粘度指标的变化,探究超声波技术对咸蛋腌制的影响。通过超声波单因素试验探究超声波处理次数、超声时间、超声功率以及超声频率对超声波辅助咸蛋腌制效果的影响,后由L₉(34)正交实验对间歇超声辅助腌制咸蛋工艺进行优化,由蛋清、蛋黄含盐率以及蛋黄出油率得出最优的间歇超声辅助腌制工艺为:超声波处理3次,超声时间30 min,超声功率350 W,超声频率20 kHz,此工艺相对传统腌制工艺,蛋清含盐率6.37%,蛋黄含盐率1.58%,蛋黄出油率达到57.53%。在保证咸蛋出油率等品质上,与传统工艺相比腌制时间缩短了15~20 d,且蛋白细嫩,咸蛋黄松沙出油,蛋黄外周黑圈等优点。     

鸭蛋清洗对咸蛋加工的影响

通过3种清洗方式(自来水、17%盐水和0.2%对羟基苯甲酸甲酯)对不同储存时间的脏鸭蛋进行处理,并将处理后的鸭蛋加工成咸蛋,结果表明:脏鸭蛋储存时间与成熟时咸蛋合格率之间存在负相关,且差异显著(p<0.05);3种清洗处理的脏鸭蛋加工的咸蛋合格率均高于对照组不清洗脏鸭蛋组;利用17%盐水清洗脏鸭蛋加工的咸蛋效果较好,且经真空高温灭菌后符合咸蛋质量要求。     

咸鸭蛋的快速腌制技术及改善其品质的研究

提出了一种缩短咸鸭蛋加工周期的方法,并对鸭蛋腌制过程中的蛋重、含油量、含盐量和含水量的变化规律进行了研究。结果显示,以上成分含量在腌制7d后,即达到了咸鸭蛋标准。     

脉动压技术腌制鸡蛋工艺优化

为提高咸蛋的腌制速率和食用品质,应用脉动压技术,选取高压幅值、高压与常压时间比为影响因素,通过单因素及正交试验,考察咸蛋腌制中蛋增重率、蛋清含盐量和蛋黄含盐量的变化,对脉动压腌制禽蛋工艺进行优化。结果表明：用饱和食盐溶液腌制48h,传质速率最佳的工艺为高压幅值135kPa、高压与常压时间比7.5min/15min。并对咸蛋品质进行感官评定,最终以高压幅值120kPa、高压与常压时间比为7.5min/15min 所腌制的咸蛋品质最佳。     

基于气相色谱-离子迁移谱分析海鸭蛋腌制过程中蛋清挥发性风味物质的变化

通过感官评定、气相色谱-离子迁移谱（gas chromatography-ion mobility spectrometry，GC-IMS）以及主成分分析和正交偏最小二乘法判别分析等多元统计学方法对海鸭蛋腌制过程中蛋清挥发性风味物质的变化进行研究。共鉴定出43 种挥发性有机化合物（volatile organic compounds，VOCs），VOCs的数量由高到低依次为酯类、酮类、醛类、酸类和醇类等。贯穿腌制过程共鉴定出20 种特征性化合物，分别为乙酸乙酯、3-羟基-2-丁酮、正丙醇、异丁酸、醋酸异丙酯、2,3-丁二酮、3-甲基-3-丁烯-1-醇、丙酸、2-甲基丁醛、乙酸丙酯、正丁醛、2-丁酮、异丙醇、异戊醛、异丁酸乙酯、四氢呋喃、2-戊酮、正丁醇、异戊醇与反式-2-戊烯醛，其中异丁酸和丙酸是咸蛋清呈现腥味的主要物质。新鲜鸭蛋中2-丁酮含量最高，腌制5 d后，乙酸乙酯成为咸蛋清中含量最高的挥发性化合物，腌制25 d后异丁酸和丙酸的相对比例逐渐升高，正丁醛和异戊醛在腌制过程中相对含量逐渐升高。根据不同阶段的特征风味物质，可以对腌制过程进行明显区分，利用GC-IMS技术对风味物质的鉴定为区分海鸭蛋的特有风味及判断腌制中海鸭蛋的品质变化规律提供了理论参考。     

咸蛋黄成熟机制及品质影响因素研究进展

论述咸蛋黄在腌制中的蛋黄指数、出油、起沙的变化规律及其品质影响因素,归纳出成熟机制主要是食盐的渗透作用和脱水作用引起蛋内物理化学性质变化。腌制温度、腌制方法、保藏时间、食盐用量、酸性、碱性添加剂等因素都会影响蛋黄品质,在加工中对其进行控制,对提高产品的稳定性和质量会有所帮助。