贮藏温度-时间变化对壳蛋新鲜度影响研究

该文以新鲜罗曼粉壳蛋为研究对象,研究5个贮藏温度-时间变化组壳蛋新鲜度指标变化,分别于0、10、20、30 d检测所有实验组壳蛋失重率、气室高度、哈夫单位、蛋黄指数、浓稀蛋白比、蛋清pH。结果表明,贮藏期间壳蛋失重率、气室高度和蛋清pH显著升高（P<0.05）,哈夫单位、蛋黄指数和浓稀蛋白比显著下降（P<0.05）。贮藏20 d时,处理组5壳蛋哈夫单位和蛋黄指数显著高于（P<0.05）对照组1、处理组1、处理组2和处理组3,而失重率、气室高度、蛋清pH较低（P<0.05）。贮藏30 d时,处理组5壳蛋失重率和气室高度显著低于对照组1、处理组1和处理组3（P<0.05）,蛋黄指数显著高于对照组1、处理组2、处理组3、处理组4（P<0.05）。除失重率、哈夫单位外,对照组2与处理组5壳蛋新鲜度指标整体差别不大。因此,除了壳蛋自身品质外,需要尽可能延长低温（4 ℃）贮藏时间,延缓壳蛋新鲜度指标劣变。     

鸡蛋壳暗斑对鸡蛋贮藏性能的影响

文章探讨了鸡蛋壳具有0%,10%,30%,60%的暗斑覆盖率对贮藏中鸡蛋失重率、相对密度、蛋黄指数、蛋清pH值、哈夫单位等新鲜度指标及菌落总数、大肠菌群、霉菌、沙门氏菌等微生物的影响。结果表明,在鸡蛋存放期间,暗斑鸡蛋新鲜度指标的变化速度以及菌落总数、霉菌等微生物的增长速度均较无斑鸡蛋快,且随着鸡蛋壳暗斑覆盖率的增加,鸡蛋新鲜度下降越快,菌落总数、霉菌等微生物的增长也越快。鸡蛋壳暗斑的存在对鸡蛋品质具有不良影响,可使鸡蛋贮藏期缩短。     

新疆特色油脂对鸡蛋涂膜保鲜效果的影响

通过考察22℃贮藏50 d过程中鸡蛋内部品质(失重率、蛋黄水分含量、哈弗单位(HU)、蛋黄指数及蛋清p H)的变化,比较分析不同类型涂膜剂对鸡蛋的保鲜效果。研究结果表明:贮藏过程中鸡蛋失重率、蛋清p H、水分含量显著增加而蛋黄指数和哈弗单位显著下降(p0.05),且贮藏时间越长,涂膜剂对鸡蛋内部品质的影响越显著。贮藏50 d后,油脂和乳液涂膜组(3.0%)鸡蛋的失重率显著低于未涂膜组(18.0%)和壳聚糖涂膜组(11.2%);未涂膜和壳聚糖涂膜组的蛋黄指数、哈弗单位在贮藏后呈现显著下降,而油脂涂膜处理的鸡蛋能够保持较高的新鲜度。未涂膜组和壳聚糖涂膜组的蛋清p H从8.51分别上升至9.07和8.92,而油脂涂膜组则略有降低。然而,涂膜剂的类型对蛋黄水分的影响不显著。研究结果表明实验油脂特别是亚麻籽油对贮藏鸡蛋的内在品质具有显著的保护作用。     

气调包装、清洗涂膜及紫外杀菌处理对鸡蛋品质影响的比较分析

为研究不同贮藏方式对鸡蛋品质的影响,采用气调包装、清洗涂膜和紫外杀菌的组合处理方式,将新鲜鸡蛋分为6组,对其进行贮藏保鲜实验。在室温下贮藏42 d,测定鸡蛋失重率、哈夫单位、蛋黄指数、蛋清p H以及菌落总数的变化,并对蛋壳表面的真菌情况进行了初步的分析。结果显示:各气调包装组均能有效抑制失重率和蛋清p H的上升,并能有效抑制鸡蛋哈夫单位和蛋黄指数的降低,与对照组差异显著(p≤0.05);清洗涂膜能在一定程度上保鲜鸡蛋,但与对照组相比,鸡蛋的失重率、哈夫单位、蛋黄指数、蛋清p H等指标差异不显著;清洗涂膜和紫外处理对蛋壳表面的细菌具有良好的抑制作用;PCR测序结果显示蛋壳表面的真菌共计13种,以赛氏曲霉(Aspergillus sydowii)为主,占蛋壳表面真菌总量的80.91%。结论:经过清洗涂膜、紫外杀菌和气调包装复合处理的鸡蛋在贮藏期(42 d)内,失重率、哈夫单位、蛋黄指数、蛋清p H和细菌菌落总数等品质指标均优于其他处理组,能最大程度抑制鸡蛋腐败变质。     

贮藏温度变化对壳蛋新鲜度的影响

该文以新鲜罗曼粉壳蛋为研究对象,研究4个贮藏温度变化处理组壳蛋新鲜度指标的变化,分别于0、10、20、30 d检测所有实验组壳蛋失重率、气室高度、哈夫单位、蛋黄指数、浓稀蛋白比和蛋清pH。结果表明,贮藏10～30 d,处理组2、处理组3、处理组4的失重率显著升高(P<0.05),而气室高度和浓稀蛋白比显著降低(P<0.05),除对照组外,所有处理组壳蛋pH呈现先升高后下降的趋势,处理组3和处理组4的蛋黄指数下降趋势更为明显。对照组和处理组1壳蛋的哈夫单位、蛋黄指数和浓稀蛋白比显著高于(P<0.05)处理组3和处理组4。在贮藏10～20 d时,处理组2的壳蛋pH显著高于(P<0.05)对照组和处理组1。因此,如果前10 d常温贮藏温度≥20℃时,引起壳蛋失重率的增加和哈夫单位的下降,与低温(4℃)贮藏相比,采用贮藏温度变化(常温-低温)贮藏壳蛋更容易引起壳蛋新鲜度指标的下降。     

含茶多酚的壳聚糖涂膜对鸡蛋保鲜效果的影响

用茶多酚和壳聚糖制成的复合涂膜液对鸡蛋进行涂膜处理,以感官指标、失重率、蛋黄指数、蛋清pH值、哈夫单位为质量指标定期取样分析测定,研究所制成的涂膜液在室温条件下对鸡蛋的保鲜效果。结果表明,和对照相比,含茶多酚的壳聚糖涂膜液能较好地保持鸡蛋的新鲜度和品质,尤其以1.5%的壳聚糖溶液联合200mg/kg茶多酚制得的涂膜液保鲜效果最好,经此涂膜液处理后的鸡蛋室温下贮存35d,失重率为1.89%,蛋黄指数为0.26,哈夫单位为60.109,蛋清pH值为8.20。     

竹汁联合壳聚糖对鸡蛋涂膜保鲜效果的影响

用竹汁和壳聚糖制成的复合涂膜液对鸡蛋进行涂膜处理,以失重率、蛋黄指数、蛋清pH值、哈夫单位、相对密度为质量指标定期取样分析测定,研究复合涂膜在室温条件下对鸡蛋生理和品质的影响。结果表明,含竹汁的壳聚糖涂膜液能较好地保持鸡蛋的新鲜度和品质,尤其以1.5%的壳聚糖溶液联合100%的原竹汁制得的涂膜液保鲜效果最好,经此涂膜液处理后的鸡蛋室温下贮存35 d,失重率为1.89%,蛋黄指数为0.3,哈夫单位为61.559,蛋清pH值为8.23,相对密度为1.064 g/mg。     

鸡蛋新鲜度指标与贮藏天数相关性研究

目的 分析鸡蛋新鲜度指标与贮藏天数的相关性, 确定新鲜度指标数值显著变化的时间, 建立新鲜度与贮藏时间相关性模型。方法 2 d为一个时间点, 设立12个实验组, 每组5枚鸡蛋, 按照标准中鸡蛋新鲜度评定指标重复3次测定鸡蛋相对密度、气室高度、哈夫单位、蛋黄指数、pH值、失重率。根据Pearson相关系数评价贮藏天数与鸡蛋新鲜度各指标之间的相关程度, Duncan法评价贮藏天数与鸡蛋新鲜度各指标之间的差异显著程度。结果 鸡蛋新鲜度各指标与贮藏天数之间显著相关(P<0.05), 各新鲜度指标数值出现显著变化的时间各不相同, 各天数之间的鸡蛋失重量、失重率差异显著(P<0.05)。结论 本研究所建立的鸡蛋新鲜度与贮藏时间的相关性模型, 可作为鸡蛋新鲜度评价模型。     

壳聚糖涂膜对鸡蛋品质的影响

通过对新鲜鸡蛋涂擦不同质量浓度的壳聚糖溶液,旨在研究壳聚糖对鸡蛋品质的影响。试验将300 枚新鲜鸡蛋随机分成6 组,分别涂上0、0.5、1.0、1.5、2.0g/100mL 和2.5g/100mL 壳聚糖溶液,25℃条件下贮存5周。每周从每个处理中取10 枚鸡蛋测定鸡蛋失重率、哈夫单位、蛋黄指数和蛋清pH 值。结果表明,第5 周与第1 周相比,不涂壳聚糖的鸡蛋失重率和蛋清pH 值显著升高(P ＜ 0.05)、哈夫单位和蛋黄指数显著低(P ＜ 0.05) 。5 周时,与不涂壳聚糖的鸡蛋相比,所有涂壳聚糖的鸡蛋失重率显著降低(P ＜ 0.05),蛋黄指数显著升高(P ＜ 0.05);涂1.0、1.5、2.0g/100mL 和2.5g/100mL 壳聚糖的鸡蛋哈夫单位显著升高(P ＜ 0.05),蛋清pH 值显著降低(P ＜ 0.05);涂1.5、2.0g/100mL 和2.5g/100mL 壳聚糖的鸡蛋间比较,蛋质量损失率、哈夫单位、蛋黄指数和蛋清pH 值差异均不显著(P ＞ 0.05)。用0.5g/100mL 壳聚糖涂擦的鸡蛋5 周时降到C 级,相当于不涂壳聚糖的鸡蛋3 周时的级别;用1.0、1.5、2.0g/100mL 和2.5g/100mL 壳聚糖处理的鸡蛋5 周时降到B 级,相当于不用壳聚糖处理的鸡蛋2 周时的级别。该实验证明壳聚糖能够延长鸡蛋货架期。     

不同处理对绿壳鸡蛋保鲜效果的研究

采用三种不同的处理方法对绿壳鸡蛋进行保鲜效果的研究,测定了鸡蛋的外部品质和内部品质的变化。结果表明,涂膜组效果最好,其次为热处理组。哈夫单位(H.U)和蛋黄指数与蛋的新鲜度呈显著的正相关;挥发性盐基氮(TVBN)含量与新鲜度呈显著的负相关。第21d开始,三个处理组间的哈夫单位和蛋黄指数有显著的差异(P<0.05);第28d时,对照组、热处理组和涂膜组挥发性盐基氮含量分别为9.095、8.270和7.560mg/100g,差异显著(P<0.05)。蛋壳厚度、蛋壳强度、蛋黄颜色、气室直径和胆固醇含量在各处理组间没有显著的差异(P<0.05)。     

Multiplication of Salmonella enteritidis in egg yolks after inoculation outside, on, and inside vitelline membranes and storage at different temperatures

Prompt refrigeration to restrict bacterial growth is important for reducing eggborne transmission of Salmonella enterica serovar Enteritidis (SE). The nutrient-rich yolk interior is a relatively infrequent location for initial SE deposition in eggs, but migration across the vitelline membrane can result in rapid bacterial multiplication during storage at warm temperatures. The objective of the present study was to measure the multiplication of SE in yolks after introduction at three different locations and subsequent storage at a range of temperatures. Using an in vitro egg contamination model, approximately 100 CFU of SE was inoculated either inside yolks, onto the exterior surface of vitelline membranes, or into the adjacent albumen. After storage of samples from each inoculation group at 10, 15, 20, and 25°C for 24 h, SE was enumerated in yolks. For all three inoculation locations, the final SE levels in yolks increased significantly with increasing storage temperatures. At all storage temperatures, significant differences in SE multiplication were observed between inoculation sites (yolk inoculation>vitelline membrane inoculation>albumen inoculation). At 25°C, final log concentrations of 7.759 CFU of SE per ml (yolk inoculation), 2.014 CFU/ml (vitelline membrane inoculation), and 0.757 CFU/ml (albumen inoculation) were attained in yolks after storage. These results demonstrate that, even when the initial site of SE deposition is outside the egg yolk, substantial multiplication supported by yolk nutrients can occur during the first day of storage and the risk of bacterial growth increases at higher ambient storage temperatures.     

The vitelline membrane: Dynamics of cholesterol metabolism in hens' eggs

Changes in cholesterol levels in egg contents were studied to indicate trends and dynamics of processes of penetration through the vitelline membrane from yolk to egg white. Investigations were carried out on eggs stored for a period of 35 days at room temperature (22°C). Levels of free and esterified cholesterol were determined by the spectrophotometric method at 7-day intervals. The selective character of the vitelline membrane depends on conditions and period of storage. The study demonstrated that the vitelline membrane loses its selective nature between the twentieth and thirtieth days under particular conditions of storage. Following this period, a spontaneous penetration of cholesterol into the egg white is observed—i.e. the barrier equilibrium of the membrane becomes unstable. The presence of free cholesterol in egg white may be indicative of loss of egg freshness.     

壳聚糖涂膜鸡蛋贮藏中品质变化的动力学模型

为研究壳聚糖涂膜鸡蛋在贮藏过程中品质变化与贮藏时间的相关性,本文利用统计软件对5、10、15、20、35 ℃下贮藏的壳聚糖涂膜鸡蛋的气室直径、重量、蛋黄系数和哈夫单位随贮藏时间变化的数据进行拟合,建立动力学模型。结果表明,壳聚糖涂膜鸡蛋的气室直径可以建立零级动力学模型,重量、蛋黄系数和哈夫单位可以建立一级动力学模型。且根据建立的模型,计算得到预测值与实测值拟合曲线的决定系数R2分别为:0.9797(气室直径)、0.9601(重量)、0.9786(蛋黄系数)和0.991(哈夫单位),并且其平均相对误差w分别为1.95%、0.53%、7.66%和2.84%,均小于10%。说明本文建立的模型可分别预测壳聚糖涂膜鸡蛋的气室直径、重量、蛋黄系数和哈夫单位在5~35 ℃范围内的变化情况和壳聚糖涂膜鸡蛋的贮藏期,为壳聚糖涂膜鸡蛋的贮藏和销售提供参考。     

Effect of refrigeration on in vitro penetration of Salmonella enteritidis through the egg yolk membrane

Internally contaminated eggs have been implicated as leading sources of transmission of Salmonella Enteritidis (SE) to humans. Although SE is not often deposited inside the nutrient-rich yolks of naturally contaminated eggs, penetration through the vitelline membrane to reach the yolk contents could result in rapid bacterial multiplication. In previous studies, such penetration has been observed occasionally at warm temperatures during experiments with in vitro egg contamination models. The present study was conducted to determine whether refrigeration affects the frequency of in vitro SE penetration of the egg yolk membrane. After inoculation of small numbers of SE onto the outside of the vitelline membranes of intact yolks, immediate refrigeration of contaminated samples prevented the penetration of SE into the egg yolk contents during 24 h of storage. However, SE penetrated inside the yolk contents in 4% of contaminated egg samples refrigerated after 2 h of storage at 30 degrees C, 15% of samples refrigerated after 6 h of storage at 30 degrees C, and 40% of samples stored at 30 degrees C for 24 h (48 samples per treatment group). These results highlight the value of prompt refrigeration for restricting the opportunities for SE to multiply to high numbers inside the yolks of contaminated eggs.     

Combination of Super Chilling and High Carbon Dioxide Concentration Techniques Most Effectively to Preserve Freshness of Shell Eggs during Long-Term Storage

ABSTRACT:  This study was made to examine the combined effects of stored temperature and carbon dioxide atmosphere on shell egg quality. The shell eggs were packed into polyethylene terephthalate/polyethylene (PET/PE) pouches and stored at 0 °C (super chilling), 10 °C, and 20 °C, respectively for 90 d. The atmospheric carbon dioxide concentration was controlled to obtain the 3 concentration levels of high (about 2.0%), medium (about 0.5%), and low (below 0.01%). Changes in Haugh unit (HU) values, weakening of vitelline membranes, and generation of volatiles were analyzed to evaluate the freshness of shell eggs. Results showed that, compared with the other combinations, the technique of super chilling and high carbon dioxide concentration enabled shell eggs to be most effectively stored for 90 d, based on estimations of the statistical significances of differences in HU values, and on maintaining the initial HU values during storage. In addition, the storage of shell eggs using this combination technique was found to significantly prevent the weakening of the vitelline membrane based on the estimations of numbers of eggs without vitelline membrane breakage when eggs broke, and significantly lowered the incidence of hexanal in the yolk from exposure to the gas chromatographic-mass spectrometric analyses of volatiles. Thus, these results confirmed that the combination of super chilling and high carbon dioxide concentration was the most effective technique for preserving shell eggs during a long term of 90 d compared with other combination techniques.     

阻抗法检测鸡蛋新鲜度

鸡蛋在贮存过程中会发生一系列物理化学变化。在实际生活中,多以感官来衡量鸡蛋的新鲜度。本实验通过设立不同贮存条件,对不同温度(4、25℃)、不同相对湿度(75%、85%、98%)组合下的6组不同条件贮存过程中鸡蛋的哈夫单位、蛋黄指数、pH值以及相对应的阻抗进行检测。结果表明,在不同条件贮存过程中鸡蛋新鲜度指标哈夫单位、蛋黄指数、pH值与阻抗之间表现出了较好的相关性,建立标准曲线,通过阻抗值的大小对应标准曲线可计算鸡蛋新鲜度。阻抗法检测鸡蛋新鲜度具有操木作简便、快速、结果准确等优点,可为蛋品企业鸡蛋的保存提供一定的理论依据。     

壳蛋新鲜度评价、影响因素及保持的研究进展

壳蛋新鲜度是衡量壳蛋品质的关键要素,本文梳理壳蛋新鲜度的评价方法、影响因素以及延缓壳蛋新鲜度指标劣变的方法,并对未来壳蛋新鲜度的研究方向进行展望。无损检测和有损检测法相结合能客观、动态、实时评价壳蛋新鲜度。蛋鸡年龄、饲料配方、贮运和环境条件等对壳蛋新鲜度影响较大,选用年轻蛋鸡、全营养饲料配方、低温贮藏、减少贮运过程中机械损伤可较好地维系壳蛋新鲜度特性。杀菌、包装、涂膜法可延缓壳蛋新鲜度指标的劣变,部分/全部采用绿色、高效、节能型非热杀菌方式,活性、可生物降解型智慧包装/涂膜技术,可有效抑制壳蛋微生物繁殖引起的腐败变质,延缓壳蛋新鲜度指标的劣变。未来壳蛋新鲜度的研究可以围绕无损检测技术、饲料配方、模拟实际生产、贮运销售环节,优化非热杀菌-包装涂膜技术等开展,以期为实现壳蛋品质提升与蛋品产业升级提供更多思路。