Tyrian Purple Precursors in the Egg Masses of the Australian Muricid, Dicathais orbita: A Possible Defensive Role

We report a putative defensive role for the precursors of Tyrian purple in the egg masses of the Australian muricid, Dicathais orbita. The fresh egg masses contain a high proportion of tyrindoleninone, which reacts to form tyriverdin and subsequently Tyrian purple and 6-bromoisatin as the eggs develop and the larvae hatch. Antimicrobial testing revealed that tyrindoleninone is toxic to both marine and human pathogens at a concentration of 1 mg/ml. Tyriverdin inhibits the growth of two marine pathogens, as well as the yeast Candida albicans at 0.001 mg/ml and was effectively bacteriostatic at 0.0005 mg/ml against three human pathogenic bacteria. Tyriverdin did not appear to significantly lyse the microbial cells. 6-Bromoisatin has mild antimicrobial properties, whereas Tyrian purple exhibited no significant activity. The antimicrobial properties of these compounds and changes in their presence during egg development correlates with ripening in the egg masses of D. orbita. This is the first report of the chemical ripening of eggs in a marine environment.     

Effects of Sulfhydryl Compounds,Carbohydrates, Organic Acids,and Sodium Sulfite on the Formation of Lysinoalanine in Preserved Egg

To identify inhibitors for lysinoalanine formation in preserved egg, sulfhydryl compounds (glutathione, L‐cysteine), carbohydrates (sucrose, D‐glucose, maltose), organic acids (L‐ascorbic acid, citric acid, DL‐malic acid, lactic acid), and sodium sulfite were individually added at different concentrations to a pickling solution to prepare preserved eggs. Lysinoalanine formation as an index of these 10 substances was determined. Results indicate that glutathione, D‐glucose, maltose, L‐ascorbic acid, citric acid, lactic acid, and sodium sulfite all effectively diminished lysinoalanine formation in preserved egg albumen and yolk. When 40 and 80 mmol/L of sodium sulfite, citric acid, L‐ascorbic acid, and D‐glucose were individually added into the pickling solution, the inhibition rates of lysinoalanine in the produced preserved egg albumen and yolk were higher. However, the attempt of minimizing lysinoalanine formation was combined with the premise of ensuring preserved eggs quality. Moreover, the addition of 40 and 80 mmol/L of sodium sulfite, 40 and 80 mmol/L of D‐glucose, 40 mmol/L of citric acid, and 40 mmol/L of L‐ascorbic acid was optimal to produce preserved eggs. The corresponding inhibition rates of lysinoalanine in the albumen were approximately 76.3% to 76.5%, 67.6% to 67.8%, 74.6%, and 74.6%, and the corresponding inhibition rates of lysinoalanine in the yolk were about 68.7% to 69.7%, 50.6% to 51.8%, 70.4%, and 57.8%. It was concluded that sodium sulfite, D‐glucose,L‐ascorbic, and citric acid at suitable concentrations can be used to control the formation of lysinoalanine during preserved egg processing.     

蛋清、蛋黄溶液的通电加热特性研究

研究了温度、蛋清、蛋黄浓度和电压对蛋清溶液和蛋黄溶液的电导率的影响;研究了蛋清、蛋黄浓度和电压对蛋清溶液、蛋黄溶液加热速率的影响。结果表明,蛋清溶液、蛋黄溶液的电导率随温度、蛋清和蛋黄浓度和电压的增高而增大,且电导率与温度呈线性关系;加热速率随蛋清和蛋黄浓度和电压的增高而加快,且温度与时间呈指数关系。     

Microparticulation by Jet Mill Grinding of Protein Powders and Effects on Hydrophobicity

A method was studied for microparticulation of protein for use as fat substitutes by superfine grinding. A jet mill produced particles <3 μm from egg white, casein and soybean hull. Microparticulation by grinding of egg white was easier than with casein or soybean hull. Hydrophobicity of casein increased by grinding to super fine particles but little or no effect was observed on soybean hull and egg white.     

Mineral oil-chitosan emulsion coatings affect quality and shelf-life of coated eggs during refrigerated and room temperature storage

Effects of mineral oil (MO) and 4 emulsions (prepared with different emulsifier types) of MO and chitosan solution (CH) at a fixed ratio of MO:CH = 25:75 as coating materials in preserving the internal quality of eggs were evaluated during 5 wk at 25 °C and 20 wk at 4 °C. Generally, as storage time increased, Haugh unit and yolk index values decreased whereas weight loss increased. However, MO and/or 4 emulsion coatings minimized the weight loss (<1.5%) and preserved the albumen and yolk quality of eggs (with the final B grade) for at least 3 wk longer than those observed for noncoated eggs at 25 °C. At 4 °C, all coated eggs changed from AA to A grade after 5 wk and they maintained this grade for 10 wk (5 wk longer than that of noncoated eggs). Although refrigeration (4 °C) alone could maintain the B grade of noncoated eggs for up to 20 wk, coating treatments were necessary to keep the weight loss below 2%. Compared with 4 °C, the increasing weight loss showed stronger negative correlation (P < 0.01) with the decreasing Haugh unit (-0.46 to -0.89) and yolk index (-0.36 to -0.89) at 25 °C. The emulsifier type used in this study generally did not affect the internal quality of eggs. Salmonella spp. detection was negative for all coated and noncoated eggs. This study demonstrated that MO and MO:CH emulsion coatings preserved the internal quality, prolonged the shelf-life, and minimized weight loss (<2%) of eggs.     

Immunoglobulin Separation from Egg Yolk: A Serial Filtration System

A serial filtration system was developed for separating immunoglobulin from egg yolk (IgY). Egg yolk was diluted 10 times with water, adjusted to pH 5.0, frozen, then thawed. The diluted yolk was diafiltered through a hard filter paper at 4-6°C to produce a clear water-soluble fraction (WSF). The WSF was then delipidated by filtering through a hydrophobic membrane filter. Ultrafiltration of delipidated WSF at pH 9.0, at 4-6°C, in the presence of 1.5M NaCl resulted in electrophoretically pure (>90%) IgY with a recovery of about 92%. Advantages of this method are the use of only a few mild chemicals and the potential of developing a continuous process.     

Influence of packaging atmosphere on the formation of cholesterol oxides in γ-irradiated egg powder

In a previous work the effect of ionising radiation on formation of cholesterol oxidation products (COPs) under aerobic conditions was studied. In the present work the influence of aerobic and anoxic conditions have been comparatively investigated to study the chemical changes of cholesterol in γ-irradiated egg powder. The irradiation treatment was carried out with powdered egg packed under air and also under vacuum in polyethylene (PE) bags and in laminated, oxygen impermeable three-layer (polyester-aluminium-polyethylene) foil to dosage levels 2 and 4 kGy at room temperature. The cholesterol oxidation is demonstrated by thin-layer chromatograms. In the egg powder wrapped in PE bags the predominant cholesterol derivatives?7-hydroxycholesterol isomers (α and β)—accumulated in significant amounts (increasing with dose) while vacuum-packaging in laminated foil considerably suppressed the quantity of these products and prevented the formation of cholesterol 5α, 6α-epoxide as well as 7-ketocholesterol. Little or no change was observed in non-irradiated (control) vacuum-packed egg powder stored at approximately 22°C for up to 5 months. Peroxide values showed changes parallel to the formation of COPs.     

Influence of pH-Induced Unfolding and Refolding of Egg Albumen on Its Foaming Properties

ABSTRACT: The foaming properties of egg albumen, which had been subjected to low and high pH unfolding followed by refolding, were investigated. The foaming capacity of egg albumen, the stability of the foam, or both, could be improved by an unfolding and refolding regime by choosing proper unfolding and refolding pH values. The foaming capacities of egg albumen were greatly improved when the refolding was at pH 6.5, 7.5, or 8.5, whereas the foaming capacities could be either slightly increased or decreased when the refolding was at pH 4.5 or 5.5 compared with the controls. The foam stability was in almost all cases improved by the unfolding and refolding treatments except for a few cases of unfolding at pH 1.5 or 10.5. The foam stability and liquid drainage were improved most when the unfolding was at pH 12.5. Analysis of total and surface sulfhydryl groups, surface hydrophobicity, and protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) provided strong evidence that the partial unfolding of egg albumen proteins as well as the interactions among egg albumen proteins through disulfide and/or hydrophobic groups dictated the improvements in foaming properties. The increase in surface hydrophobicity showed better correlation with the improvement of foaming properties than the change of surface sulfhydryl content did.     

How micro-phase separation alters the heating rate effects on globular protein gelation

This study was conducted to determine how the combination of heating rate and pH can be used to alter viscoelastic properties and microstructure of egg white protein and whey protein isolate gels. Protein solutions (1% to 7% w/v protein, pH 3.0 to 8.5) were heated using a range of heating rates (0.2 to 60 °C/min) to achieve a final temperature of 80 °C. The gelation process and viscoelastic properties of formed gels were evaluated using small strain rheology. Single phase or micro-phase separated solution conditions were determined by confocal laser scanning microscopy. In the single phase region, gels prepared by the faster heating rates had the lowest rigidity at 80 °C; however, a common G' was achieved after holding for 4 h at 80 °C . On the other hand, under micro-phase separation conditions, faster heating rates allowed phase separated particles to be frozen in the network prior to precipitation. Thus, gels produced by slower heating rates had lower rigidities than gels produced by faster heating rates. The effect of heating rate appears to depend on if the solution is under single phase or micro-phase separated conditions. PRACTICAL APPLICATION: The effect of heating rate and/or time on protein gel firmness can be explained based on protein charge. When proteins have a high net negative charge and form soluble aggregates, there is no heating rate effect and gels with equal firmness will be formed if given enough time. In contrast, when electrostatic repulsion is low, there is a competition between protein precipitation and gel formation; thus, a faster heating rate produces a firmer gel.