关于鸡蛋黄、鸭蛋黄、咸鸡蛋黄、咸鸭蛋黄四种蛋黄风味物质的研究

咸蛋因其鲜嫩可口,营养丰富是一直深受国内外消费者喜欢的传统美食.尤其是咸蛋黄不仅可以直接食用,还被用于添加至月饼等糕点中,提高产品的口感与营养.鸡蛋、鸭蛋经腌制后产生了更多宜人的口感和风味.文章运用顶空微萃取技术与气质联用相结合的方法对鸡蛋黄、鸭蛋黄、咸鸡蛋黄和咸鸭蛋黄四种蛋黄进行了挥发性风味物质的研究.     

原料蛋黄粉中锌含量的检测

目的 建立原料蛋白粉中锌含量的简便检测方法。方法 蛋黄粉待测样品经微波消解, 加入5 mL浓硝酸后缓慢振摇几次, 再加入2 mL过氧化氢放置5 min, 拧紧盖子在微波消解设备中进行充分消解, 冷却后在带孔式电热板上赶酸至1 mL, 用2%的盐酸溶液转移至50 mL容量瓶中, 摇匀。结果 该检测方法仪器检出限为0.092 mg/kg, 在元素线性范围内相关系数R为0.999以上, 回收率为97.2%~101.5%。结论 本检测方法操作步骤简便, 检测结果准确可靠。     

Emulsifying characterization of hens egg yolk proteins in oil-in-water emulsions

Emulsifying properties of egg yolk as a function of pH and oil volume were studied. Egg yolk proteins formed larger emulsion particles at pH 3 and the mean droplet size of the emulsions was decreased with increasing pH. A linear relationship between turbidity and mean droplet size of egg yolk emulsions could not be obtained. This may be due to the floculation of the emulsions. Egg yolk proteins formed thicker multilayers at low oil volume, however total protein adsorption ratio against original proteins was 55–65%, independent to protein and oil concentration. Electrophoretic analysis of the egg yolk emulsion revealed that the main components to adsorb at the interface was glanular lipovitellins, even though its emulsifying property was lower than that of plasma because of poor solubility at low ionic strength (0.1 M NaCl) at pH 7. These results indicate that the main contributor for egg yolk emulsion is granules and it can affect the emulsifying properties of egg yolk at different pH values.     

Novel extraction technologies and potential applications of egg yolk proteins

Food Science and Biotechnology - The high nutritional value and diverse functional properties of egg yolk proteins have led to its widespread use in the fields of food, medicine, and cosmetics....     

Solubility of egg yolk proteins: modelling and thermodynamic parameters

Solubility of systems containing egg yolk proteins and xanthan gum (0.083, 0.042, 0.021 and 0.011% w/v) had been studied in different temperatures (10, 25 and 35 °C), pH (3.0, 4.0, 6.5, 8.5 and 10.0) and concentration of NaCl (0.2, 0.4 and 0.8) mol/L. According to the data, a lesser solubility of the proteins can be observed in the pH system that is more acid. An increase in the solubility of the proteins of the egg yolk can also be observed in high concentrations of xanthan gum associated with the increase of NaCl concentration. The nonlinear model used to adjust gave a good fit adjusted to the solubility data in the studied conditions. The thermodynamic parameters were calculated indicating that the entropic effects in the solubility process are more important than the enthalpic effect. The negative values found for free energy indicate the spontaneity of the process of the solubility of the proteins and their viability.     

Thermal behaviour of lyophilized egg yolk and egg yolk fractions

Despite its importance from a technical point of view, the influence of temperature on rheological behaviour of lyophilized egg yolk and egg yolk fractions has not yet been studied. In this work, the effect of temperature on rheological properties of these products have been analysed by means of stationary and oscillatory measurements. Firstly, the Arrhenius equation was employed to assess the influence of temperature on viscosity. In addition to temperature effect, solid content showed to be determinant on viscosity, while particle size, water holding capacity and wettability influence on rheological behaviour of samples were not critical. Secondly, rheological changes during heat-induced gelation of the samples were also investigated by means of dynamic tests and the critical network exponents at the gelation point were calculated. An analysis of variance (ANOVA) was also performed using the Statgraphics Plus to evaluate experimental data. Results show that proteins of egg yolk fractions possess a similar network structure before and after gelation, while egg yolk structure is clearly modified by gelation process. Composition and structure is the main responsible of differences between samples.     

Detection of trichinellosis in pigs by artificial digestion and enzyme immunoassay.

The objective of this study was to demonstrate the reliability of current and proposed methods for the inspection of swine and other species for infection with the parasite Trichinella spiralis. Five groups of pigs were infected with doses of 2500, 500, 100, 50, and 20 T. spiralis larvae to establish moderate and low-level infections. Pigs were bled periodically during the study for samples to be tested by enzyme immunoassay (EIA). At the conclusion of the study, pigs were slaughtered and tissues collected for analyses of worm burdens and for comparison of digestion testing methods. Comparisons of pooled sample digestion methods were made using inspection methods prescribed by European Union Directives and the USDA, Code of Federal Regulations. Pooled sample digestion testing using 1-g samples was effective for detecting pigs with larval densities of > 10 larvae per gram (LPG) of tissue but only partially effective for pigs with infections of <3 LPG. Pooled sample digestion testing using 5-g samples detected all pigs with infection levels > 1 LPG. The EIA detected all T. spiralis-infected pigs, but did not detect infections in some pigs until 49 days after inoculation. These results demonstrate that the pooled sample digestion method using a 5-g sample size is the most effective inspection method for reducing the risk of human exposure to T. spiralis in pork.     

Determination of yolk:white ratio of egg using SDS-PAGE

Food Science and Biotechnology - The aim of present study was to determine liquid egg adulteration based on yolk:white ratio of egg using sodium dodecyl sulphate-polyacrylamide gel electrophoresis...     

Separation of the proteins of egg white and egg yolk and a study of their interactions in whole egg. I. Quantitative fractionation of proteins

Procedures developed for the fractionation and sub-fractionation of proteins in whole egg have been applied to separated white and yolk samples and to whole egg reconstituted from them. The fractionation pattern of whole egg soluble proteins on diethylaminoethylcellulose differed from a simple combination of the corresponding patterns for white and yolk soluble proteins. All the fractions and sub-fractions were dialysed and freeze-dried for analysis. The main effect of mixing yolk with white appears to be the conversion of some insoluble lipoproteins to a soluble form, the bulk of which has no affinity for diethylaminoethylcellulose but can be separated by chromatography on car-boxymethylcellulose into a number of fractions that have high lipid contents and are clearly derived from the low density fraction of yolk.     

Detection of chicken meat in raw meat mixtures by a sandwich enzyme immunoassay

A double-antibody sandwich ELISA (enzyme-linked immunosorbent assay) has been successfully developed for the detection of low levels of chicken meat (1–30%) in unheated meat mixtures. The assay uses chicken-specific antibodies, obtained by immunoadsorption of the crude chicken antisera onto immobilized sarcoplasmic extracts from beef, pig and horse, to remove cross-reacting antibodies. The purified antibodies, bound to the wells of a microtitre plate, sequester chicken muscle soluble proteins from saline extracts of meat mixtures. Immuno-recognition is made with similar purified antibodies conjugated to the enzyme horseradish peroxidase. Subsequent enzymic conversion of substrate gives clear optical density differences, when assaying minced beef and pig containing variable amounts of chicken meat.     

卵黄抗体鸡蛋粉喷雾干燥工艺研究

以活性保留率、出粉率为指标,对影响卵黄抗体鸡蛋粉喷雾干燥效果的因素进行了考察,并通过正交实验确定了最佳工艺条件为:进料速度500mL/h、蛋液质量浓度20%、进口温度160℃,此条件下出粉率达到16.23%,IgY(卵黄抗体球蛋白)活性保留率达到92.60%;各因素对出粉率的影响依次为:进口温度>蛋液浓度>进料速度。     

Adsorption of egg yolk plasma cholesterol using a hydrophobic adsorbent

Data on hydrophobic adsorption equilibrium of egg yolk plasma cholesterol were obtained using Streamline Phenyl^® resin in batch suspension at room temperature (25 °C). Influence of two types of salt (NaCl and Na₂SO₄) at four concentrations (0.0; 0.05; 0.1, and 0.2 M) on equilibrium was analyzed. Increased salt concentration reduced the amount of cholesterol adsorbed in the resin. Two isotherm models (Langmuir and a modified model based on type S-isotherm) were used to represent solid-liquid equilibrium data. The latter led to a better fit of the equilibrium data, with a 99.8% value of RSSE. A 70% reduction of the cholesterol content in the plasma was obtained with a 1:4 plasma:water dilution ratio.     

Transport of human immunoglobulin G and Fc-fusion proteins to chicken egg yolk

We examined the transport of human immunoglobulin G (IgG) subclasses and fusion proteins with the Fc region of human IgG to the egg yolk, after the proteins were injected into a vein of hens. Human IgGs were efficiently transported and accumulated into the yolk, whereas the proteins were not detected in the egg white. Among human IgG subclasses, IgG2 was transported most efficiently. Fc-fusion proteins injected were also transported into the yolk. A fusion protein with the Fc region derived from human IgG2 was more efficiently transported into the yolk than the counterpart fusion with the Fc region from human IgG1. This study shows that the recovery of recombinant antibodies and Fc-fusion proteins from the yolk is an effective method in transgenic chicken bioreactors.     

荧光免疫分析法检测食品中黄曲霉毒素的研究进展

黄曲霉毒素是迄今发现的真菌毒素中毒性最强的一类,是公认的I类致癌物,在粮食、坚果、油脂、乳及其制品等多种食品中均有发现。因此,研究出准确、快速、便捷的检测方法对保障食品安全和人类健康具有重要意义。荧光免疫分析法具有灵敏度高、准确性好、检测速度快、操作简单等优势,适合现场高通量快速筛查,近年来被广泛地用于检测食品中的黄曲霉毒素。该文介绍了4类常用的荧光标记物(荧光素、量子点、上转换纳米粒子和稀土离子螯合物),并详细阐述了5种荧光免疫分析法(荧光免疫吸附法、荧光免疫层析法、荧光偏振免疫分析、荧光共振能量转移免疫分析和时间分辨免疫分析)的检测原理,以及上述方法应用于检测食品中黄曲霉毒素的国内外最新研究进展,为今后的研究提供借鉴。     

Interactions between hydrophobically modified starch and egg yolk proteins in solution and emulsions

In this paper we study the interaction between starch which has been hydrophobically modified, with octenyl succinic anhydride (OSA), and α-β-livetin, which is the water soluble fraction of egg yolk. The modification of the starch renders it surface active and also incorporates a carboxyl group to the starch, which can be negatively charged. The interaction was studied both in solution and emulsions, and at different pH (4.0–8.0). Solutions with different ratios between starch and protein was mixed and studied with turbidity measurements over time. Emulsions were formed with α-β-livetin after which the OSA-starch was added. The emulsions were separated by centrifugation and the surface load of α-β-livetin and OSA-starch was determined through serum depletion. Furthermore, the impact of the observed interaction on emulsion stability was investigated. The results show a strong interaction between the two biomacromolecules in solution at pH 4.0. In the emulsions the adsorption of starch onto livetin was highest at pH 4.5 followed by pH 6.0, while low at pH 4.0 and 8.0. The low adsorption of OSA-starch at pH 4.0, despite the strong interaction in solution, can be explained by complex formation immediately in solution. Less starch would, thus, be able to reach the interface and adsorb. Some differences in the stability of an emulsion only containing α-β-livetin, and an emulsion with both α-β-livetin and OSA-starch could be observed. However, the differences were not statistically significant.     

Analysis of glycerophosphonolipids in egg yolk

Glycerophosphonolipids are a relatively unknown class of polar lipids. Little information is available on any special biological function of these substances or specific technological use for them. Since glycerophosphonolipids have been reported to occur in egg yolk, further studies are needed in order to determine their relevancy. However, analysis of these lipids is rather difficult, due both to their chemical similarity to phospholipids and the lack of commercially available reference substances. Therefore, a reference substance for phosphono analogues of phosphatidylethanolamine (PnE)—1,2-dioctadecanoyl-glycero-3-aminoethylphosphonate—has been synthesized and an HPLC/ELSD method to separate PnE from its phosphonoanalog was developed. Although the present results showed no evidence of glycerophosphonolipids in egg yolk (limit of detection <0.02% for PnE), the spectroscopic data gathered here do point to an approach for further analysis of glycerophosphonolipids. Furthermore, a characteristic ESI–MS² fragmentation pattern for PnE was established, which can be used as a “fingerprint” for the identification of this substance in other biological systems. It was found to be characteristic for a fatty acid fragment to be split off as an internal anhydride (ketene) [M–H–RCH=C=O]⁻ along with the whole fatty acid fragment [M–H–RCH₂COOH]⁻ in the negative ion mode. In the positive mode, there was a selective loss of only the head group of the phosphonolipid [PO₃H₂–C₂H₄–NH₃]⁺, resulting in the so-called “diacylglycerol-like fragment ion” [DAG]⁺.     

Detection of the allergenic celery protein component (Api g 1.01) in foods by immunoassay

Among food allergens, celery is a frequent cause for adverse food reactions in allergic patients. In this study, the celery allergen protein Api g 1.01 RNA was amplified by RT-PCR and cloned into the pET-32a expression vector. The recombinant plasmid was transformed into E.coli BL21(DE3) pLys for the expression of protein Api g 1.01. Monoclonal antibodies were prepared against the expressed purified Api g 1.01 protein. A sandwich enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of celery soluble proteins in processed foods was developed using the prepared monoclonal antibodies. The developed ELISA had a high specificity, although it showed slight cross-reactivity to carrot. The limit of quantification (LOQ) was 0.28 μg/mL (equivalent to 5.6 μg whole celery protein/g food sample). The recovery ranged from 83 to 115%, whereas coefficients of variation were 6.7–8.9%.