Effect of pasteurisation on the chemical composition of liquid whole egg. III.—Effect of staling and freezing on the protein fractionation patterns of raw and pasteurised whole egg

Two particular fractions of the soluble proteins were consistently reduced by heating liquid egg for 5 min at 150°F. These fractions were quantitatively greater in the soluble proteins from frozen egg. The soluble proteins appeared to be more stable to heat in eggs that had been stored for 15 days at 70°F than in new-laid eggs. Unfrozen new-laid and stale egg and frozen new-laid egg all showed an increase in insoluble material after pasteurisation, and frozen egg contained more insoluble materials than unfrozen egg. Gel filtration showed that the proportion of compounds of high molecular weight in the insoluble proteins was markedly increased by pasteurisation and even more markedly increased by freezing.     

Effect of pasteurisation on the chemical composition of liquid whole egg V.—Isolation and examination of a complex lipoprotein from pasteurised liquid egg

A high molecular weight substance isolated from the insoluble proteins of pasteurised liquid whole egg was found to be a complex lipoprotein containing 70 % lipid and 30 % protein. The lipid portion was a mixture of several different groups and the apoprotein was an extremely insoluble material with an amino acid composition that did not exactly match that of any egg protein reported in the literature but closely resembled that of vitellenin. It is postulated that this lipoprotein was derived from the low density fraction of egg yolk. A substance of lower molecular weight that was also separated from the inert fraction of insoluble proteins by gel filtration was tentatively identified as one of the lipovitellins.     

Effect of pasteurisation on the chemical composition of liquid whole egg. I. Development of a scheme for the fractionation of the proteins of whole egg

The proteins of whole egg may be separated into soluble and insoluble portions by dialysis against glycine solution followed by centrifugation at a high speed. The soluble proteins can then be resolved into at least twelve fractions by ion-exchange chromatography on diethylaminoethyl-cellulose, using stepwise elution with dilute glycine-phosphate buffer solutions containing increasing concentrations of sodium chloride. Further examination has shown that most of the fractions contain more than one protein, and some tentative identifications have been made. The insoluble proteins can be dissolved in a relatively strong phosphate buffer and fractionated on diethylaminoethyl-cellulose in a similar way. Separate examinations of white and yolk indicated that the soluble proteins of whole egg are predominantly the same as those of the white, and also showed certain differences between whole egg and the separated white and yolk that could be attributed to some form of protein association in mixed whole egg. An initial experiment has suggested that the method described will reveal differences between raw and pasteurised egg.     

Effect of pasteurisation on the chemical composition of liquid whole egg IV.—Further resolution of certain fractions of the soluble proteins

Amino acid analyses confirmed previous electrophoretic evidence that two particular chromatographic fractions from the soluble proteins of liquid whole egg were mixtures of proteins. Further resolution of these fractions has been effected by ion-exchange chromatography on carboxymethyl cellulose, using sodium acetate buffer solutions containing increasing concentrations of sodium chloride followed by certain alkaline solutions. Some distinctions between sub-fractions obtained from raw and pasteurised egg have been noted.     

Functional properties of pasteurised liquid whole egg products as affected by the hygienic quality of the raw eggs

The viscosity, foaming and baking performances of pasteurised liquid whole egg products were investigated to study the influence of raw egg hygienic quality on egg product functional performances. Uracil, lactic acid and 3OH-butyric acid measured in the pasteurised egg products were taken as chemical indices of the hygienic quality of the raw material. A high variability in the functional properties was observed, especially for overrun and foam stability, as well as in the chemical indices of hygiene. Many interesting correlations were found between variables, for example between overrun and cake volume (p < 0.001). Instead, no significant correlations were found between the chemical indices and the different functional properties. However, the application of Principal Component Analysis demonstrated that a good hygienic quality of the raw material used to prepare the liquid whole egg products is a prerequisite needed to develop good functional performances, although other factors pertaining to composition or processing also have a role.     

The immunological consequences of pasteurisation: Comparison of the response of human intestinally-derived cells to raw versus pasteurised milk

Microarray technology was used to identify differentially expressed biological signatures in human intestinal cell line (HT-29) exposed to raw versus pasteurised milk; 1041 differentially expressed genes (≥1.3 fold change) were identified (P < 0.001) between exposure groups. These were further identified to be contained within 179 gene ontologies. Genes more highly expressed (599 or 57.5%) in cells exposed to raw milk were predominately contained within immune-based gene ontologies. In contrast, genes showing lower expression in raw milk treated cells (442 or 42.5%) in comparison with pasteurised milk were involved in a broader range of cellular functions. The lowered immune function identified in cells exposed to pasteurised milk was intriguing and suggests that raw milk may be capable of inducing certain aspects of the immune system, including processes involved in T and B cell function/development. The results may indicate an alteration in the immunomodulatory potential of milk following pasteurisation.     

Texture of cooked potato II.—Relationships between intercellular adhesion and chemical composition of the tuber

In the variety Majestic, statistically significant relationships were found between intercellular adhesion and the levels of tuber starch, amylose, polyuronide, calcium and magnesium. It is suggested that the relationship between intercellular adhesion and a particular constituent may be modified by the levels of the other constituents. a mechanism is proposed for the action of amylose in influencing intercellular adhesion. the differences in intercellular adhesion, and in the levels of the various intrinsic factors, were produced by feeding plants different nutrient solutions (various chloride/nitrate ratios) or by maintaining different moisture regimes.     

热处理对于鸡蛋全蛋液功能性质的影响

研究了不同强度的热处理条件(处理温度61、64、67℃,处理时间2.5、3.5、4.5min)对于鸡蛋全蛋液蛋白质的溶解性、乳化性、起泡性、表面疏水性和表面巯基含量的影响。结果表明:随着加热温度的升高和处理时间的延长,全蛋液蛋白质溶解度与泡沫稳定性不同程度的下降,而表面疏水性、表面游离巯基含量、乳化稳定性则不同程度的提高。当温度高于61℃时,全蛋液起泡性随温度升高和时间的延长而降低,同时,研究还发现热处理对于全蛋液乳化活力的影响不明显。      

Effect of applying increasing levels of nitrogen to ryegrass: II.—Amino acid composition of peptide and protein fractions

Amino acid concentrations in the peptide fraction of S22 ryegrass increased with total N content but when amino acid N was expressed as percentage of peptide N little variation was noted with increasing maturity or with increasing level of N application. Also under these conditions true protein increased but when expressed as a percentage of total protein N there was little change in the amino acid make-up of this fraction. Total dicarboxylic amino acid N and amide N maintained a 1 : 1 ratio in the peptide fractions under these conditions. Glycine and phenylalanine contents were relatively higher in the peptide fractions, and leucine and valine contents were relatively higher in the protein fractions. Proline content was unusually high in the free state, intermediate in the peptide fraction and lowest in the proteins. The amino acid make-up of the peptide fraction was more closely related to the protein fraction than to the free amino acid fraction and the free amino acids and their amides had some influence in determining the composition of the peptide fraction.     

均质处理对鸡蛋全蛋液功能性质的影响

为了明确全蛋液均质处理对其功能性质影响规律,对不同压力均质处理后全蛋液蛋白溶解度、起泡性、乳化性、凝胶强度等功能性质及应用全蛋液制作的海绵蛋糕比容的变化进行了研究。结果表明:在5～40 MPa压力内,随着均质压力的升高,全蛋液起泡力、乳化活力和海绵蛋糕比容明显降低,泡沫稳定性和凝胶强度明显提高,乳化稳定性的变化比较复杂,蛋白质溶解度基本保持稳定。在实际生产中需要根据全蛋液应用时所侧重的功能性质选择适宜的均质条件。     

超声波处理对全蛋液流变特性的影响

采用不同超声声能密度(0.4,0.8,1.2,1.6,2.0 W/g)及超声作用时间(0,5,10,15,20 min)对全蛋液进行处理,再用流变仪测其流变特性。试验结果表明,全蛋液是一种假塑性非牛顿流体,具有剪切稀化现象,其流变曲线在温度为0～40℃时服从Herschel-Bulkley模型。随着超声作用时间及声能密度的增大,全蛋液的流变特性指数增大,屈服应力及黏稠系数减小,流动性增加,全蛋液的非牛顿流体特性减弱,牛顿流体特性增强。动态流变试验结果表明,随着超声作用时间及声能密度的增大,全蛋液的损耗模量G"和贮能模量G'均减小,说明全蛋液的黏性特征和弹性特征均减弱,流动性增强,与静态流变试验结果一致。     

盐和糖对全蛋液耐热性能的影响研究

为了寻找一种提高鸡蛋全蛋液耐热性能的方法,对添加适量蔗糖和氯化钠的全蛋液的凝胶形成温度及功能性质进行了初步研究 结果表明,添加8％蔗糖或8％ NaCl均可以显著增强全蛋液的耐热性能,使全蛋液的凝胶形成温度提高至73℃以上,且添加蔗糖与NaCl可以不同程度的改善全蛋液的功能性质,使全蛋液经过70℃热处理后仍能保持优良的溶解度、乳化性和起泡性,但其凝胶强度略微降低.通过添加蔗糖和NaCl可以使全蛋液耐受杀菌温度提高5℃以上,对于提高全蛋液卫生安全性、保持良好功能性质具有重要的实际意义.     

盐和糖对全蛋液耐热性能的影响研究

为了寻找一种提高鸡蛋全蛋液耐热性能的方法,对添加适量蔗糖和氯化钠的全蛋液的凝胶形成温度及功能性质进行了初步研究。结果表明,添加8%蔗糖或8%NaCl均可以显著增强全蛋液的耐热性能,使全蛋液的凝胶形成温度提高至73℃以上,且添加蔗糖与NaCl可以不同程度的改善全蛋液的功能性质,使全蛋液经过70℃热处理后仍能保持优良的溶解度、乳化性和起泡性,但其凝胶强度略微降低。通过添加蔗糖和NaCl可以使全蛋液耐受杀菌温度提高5℃以上,对于提高全蛋液卫生安全性、保持良好功能性质具有重要的实际意义。      

Separation of the proteins of egg white and egg yolk and a study of their interactions in whole egg. 3. Amino-acid composition of protein fractions

A number of the fractions and sub-fractions isolated from the soluble proteins of white, yolk and whole egg have been identified by their amino-acid compositions, and others have compositions that differ from those of known proteins. It is concluded that the relative abundance of the different amino acids is similar for nearly all egg proteins. Part of the low density lipoprotein in whole egg is in a soluble form and can be partially fractionated by ion-exchange chromatography; the resulting fractions contain apoproteins with slightly differing amino-acid compositions.     

Freeze-drying of raw beef I.—Influence of some raw material variables

The effect of raw material variables, such as breed, sex, age, fat content of muscle and ageing time, upon the quality of the reconstituted product were studied in multifactorial experiments of a preliminary nature. The effects observed were in fair agreement with general experience with unprocessed raw beef and with the limited published data for reconstituted freeze-dried raw beef.     

Fractionation of plant material. III.—Two schemes for chemical fractionation of fresh leaves,having special applicability for isolation of the bulk protein

Nearly all the protein of broad-bean leaves other than cell-wall protein was readily extracted into phenol-acetic acid-water mixtures, and further purified by free-solution eletrophoresis therein, using the continuous apparatus of Hannig. Under these conditions RNA migrated cationically in association with the protein. Adding salt did not greatly improve the separation, but it reversed the relative cationic migration rates of phaeophytin a and protein. Liquid-liquid partition between phenol and aqueous buffer phases gave good separation of the protein from RNA. Scheme I involved successive extraction of the leaves with 5% (w/v) aqueous trichloroacetic acid, ethanol and phenol-acetic acid-water; the bulk of the protein went into this last solvent mixture and did not require further electrophoretic treatment. In Scheme II, components of low molecular weight were washed out from the plasmolysed leaves with water. Extraction was then carried out with phenol-acetic acid-water, and this extract was further fractionated by electrophoresis. The non-migrating fraction should be valuable starting material for studies of a variety of leaf constituents. The extraction residues are promising starting material for studies of the leaf polysaccharides and other cell-wall components. The protein preparations contained little phosphorus or carbohydrate but were brown and had high C/N ratios and higher ultra-violet absorption than corresponded to the aromatic amino acids present. This was decreased, but not abolished, by keeping the work under nitrogen. Model experiments showed good electrophoretic separation of protein from polyphenols and tannic acid under the same conditions. The extraneous aromatic material is therefore presumed to be bound covalently to the protein. Coupling of oxidatively polymerising quinones to side-chains of amino acid residues, especially lysine, seems probable. The occurrence of such reactions in leaves has implications for the nutritive value of their proteins. Such products may also contribute directly to the ‘humic acid’ fraction of soil.     

全蛋液酶解条件的优化研究

为了丰富蛋制品市场,拓展鸡蛋的加工途径,首先进行了不同种蛋白酶对全蛋液水解能力的比较试验,通过温度、pH值、底物浓度、酶浓度和水解时间等单因素对水解率的影响实验和正交实验对全蛋液的酶解条件进行了研究。结果表明：Flavourzyme为最佳用酶,当底物浓度为3％、酶浓度为0．2％、温度为50~C、pH值为6．0和水解时间为7h时,水解率可达到45％,得到了稳定性和风味较好的半透明鸡蛋酶解液,用它作为营养强化剂,可进一步研究开发系列功能食品,尤其是适合老人和冬幼儿食用的营养功能食品。     

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.     

The effect of pasteurisation and freezing on the low density lipoproteins of egg.

The low density fraction of egg yolk was separated by gel filtration into two groups of lipoproteins. One group (1) had an extremely high molecular weight and was probably formed by aggregation of the second group (2), which itself had a high molecular weight. In liquid egg the ratio of group 1 to group 2 was increased by pasteurisation for 5 min at 65°C and also by freezing and thawing of either raw or pasteurised material. When group 2 was isolated by gel filtration and then frozen and thawed it was converted to group 1.