Yolk Contamination Research Articles

Effect of Lipase and Phospholipase A1 on Foaming and Batter Properties of Yolk Contaminated Egg White.

Egg white (EW) is frequently used in bakery products because of its excellent foaming capabilities. However, egg yolk (EY) contamination often degrades the foaming characteristics of EW. The purpose of this study was to investigate the effect of different concentrations of phospholipase A1 (PLPA1) and lipase (LP) on EW. The changes in particle size distribution and potential before and after enzymatic digestion of EW with contaminated 0.5 wt% and 1.0%wt EY were tested. The foaming rate and foam stability were measured after the dispersions were digested with different concentrations of PLPA1 and LP. Additionally, the dispersion samples were used to prepare batter and angel cake, and the modulus, density, and microstructure of the batter were analyzed. Results showed that the potential absolute value increased when the EY was hydrolyzed by PLPA1. The distribution of yolk particle size showed a new aggregation and the average particle size decreased after LP hydrolysis. The dispersion samples hydrolyzed by PLPA1 and LP recovered all the properties of the samples at enzymatic concentrations of 500 U/g and 2500 U/g. This may be attributed to the changes in yolk particles resulting from the enzymatic digestion of EY and the production of amphiphilic lysophospholipids, fatty acids, and glycerol.

Determination of yolk contamination in liquid egg white using Raman spectroscopy

Purified egg white is an important ingredient in a number of baked and confectionary foods because of its foaming properties. However, yolk contamination in amounts as low as 0.01% can impede the foaming ability of egg white. In this study, we used Raman spectroscopy to evaluate the hypothesis that yolk contamination in egg white could be detected based on its molecular optical properties. Yolk contaminated egg white samples (n = 115) with contamination levels ranging from 0% to 0.25% (on weight basis) were prepared. The samples were excited with a 785 nm laser and Raman spectra from 250 to 3,200 cm−1 were recorded. The Raman spectra were baseline corrected using an optimized piecewise cubic interpolation on each spectrum and then normalized with a standard normal variate transformation. Samples were randomly divided into calibration (n = 77) and validation (n = 38) data sets. A partial least squares regression (PLSR) model was developed to predict yolk contamination levels, based on the Raman spectral fingerprint. Raman spectral peaks, in the spectral region of 1,080 and 1,666 cm−1, had the largest influence on detecting yolk contamination in egg white. The PLSR model was able to correctly predict yolk contamination levels with an R2 = 0.90 in the validation data set. These results demonstrate the capability of Raman spectroscopy for detection of yolk contamination at very low levels in egg white and present a strong case for development of an on-line system to be deployed in egg processing plants.

Quantification of egg yolk contamination in egg white using UV/Vis spectroscopy: Prediction model development and analysis

Abstract The objective of this study was to develop a statistical model for predicting egg yolk contamination level in egg white using a spectroscopic method. Eggs that were stored for 0, 0.5, 1.0, 1.5, 2.5, and 6.5 wk at 4 °C were manually processed to cleanly separate the yolk from the white. Egg white samples containing 0–0.5% (w/w) of yolk were prepared by adding yolk to the white and further diluting with the pure egg white. Transmission spectra of samples were acquired at 500 nm wavelength. The optical absorbance of the “contaminated” egg white samples positively correlated with the yolk concentration, and its intensity was affected by the freshness of eggs, egg variety, and measuring temperature. A nonlinear prediction model, or a detection function, was developed using 182 measurements to predict yolk concentration with a known storage time. This highly sensitive method was validated using 102 separate measurements.

Rapid determination of egg yolk contamination in egg white by VIS spectroscopy

In this study, a non-invasive method utilizing VIS spectroscopy for rapid and quantitative determination of yolk contamination in egg white was developed. Fresh eggs were obtained from Iowa egg production facilities and were used to prepare 210 egg white samples with various levels of yolk contamination. The simulated yolk contamination levels ranged from 0.001 to 0.1wt% in egg white (as-is basis), and the samples were subjected to spectroscopic analysis. UV–Vis–NIR spectra (200–860nm) were acquired for each sample with a spectral resolution of 2nm. The absorption bands at 430nm and 378nm were identified as the most sensitive to the yolk contamination. A quantitative predictive model was developed to correlate the two absorptions to the concentration of yolk contamination. The correlation coefficient of calibration set and validation set are 0.9830 and 0.9769, respectively. The MSE (mean squares error) of calibration set and validation set are 0.0066 and 0.0044%, respectively. The UV–VIS spectroscopy method was demonstrated to be sensitive at as low as 0.001% yolk content. It can potentially become a simple, noninvasive, and rapid and yet highly sensitive routine test as a quality control means for egg processing industry.

Effect of Plant Derived Antimicrobials on Salmonella Enteritidis Adhesion to and Invasion of Primary Chicken Oviduct Epithelial Cells in vitro and Virulence Gene Expression

Salmonella Enteritidis (SE) is a major foodborne pathogen in the United States and one of the most frequently reported Salmonella serotypes globally. Eggs are the most common food product associated with SE infections in humans. The pathogen colonizes the intestinal tract in layers, and migrates to reproductive organs systemically. Since adhesion to and invasion of chicken oviduct epithelial cells (COEC) is critical for SE colonization in reproductive tract, reducing these virulence factors could potentially decrease egg yolk contamination. This study investigated the efficacy of sub-inhibitory concentrations of three plant-derived antimicrobials (PDAs), namely carvacrol, thymol and eugenol in reducing SE adhesion to and invasion of COEC, and survival in chicken macrophages. In addition, the effect of PDAs on SE genes critical for oviduct colonization and macrophage survival was determined using real-time quantitative PCR (RT-qPCR). All PDAs significantly reduced SE adhesion to and invasion of COEC (p < 0.001). The PDAs, except thymol consistently decreased SE survival in macrophages (p < 0.001). RT-qPCR results revealed down-regulation in the expression of genes involved in SE colonization and macrophage survival (p < 0.001). The results indicate that PDAs could potentially be used to control SE colonization in chicken reproductive tract; however, in vivo studies validating these results are warranted.

Using modified soy protein to enhance foaming of egg white protein

It is well known that the foaming properties of egg white protein are significantly reduced when a small amount of yolk is mixed in the white. To improve foaming properties of yolk-contaminated egg white protein, soy protein isolate (SPI) and egg proteins were modified to make basic proteins, and effects of these modified proteins on egg white foaming were evaluated in a model and an angel cake system. SPI and egg yolk proteins were modified to have an isoelectric point of 10, and sonication was used to increase protein dispersibility after the ethyl esterification reaction. However, only the addition of sonicated and modified SPI (SMSPI) showed improvement of foaming in the 5% egg protein model system with 0.4% yolk addition. SMSPI was then used in making angel food cake to examine whether the cake performance reduction due to yolk contamination of the white would be restored by such alkaline protein. Cake performance was improved when cream of tartar was used together with SMSPI. Basic soy protein can be made and used to improve egg white foaming properties and cake performance.

Use of Mucor miehei Lipase to Improve Functional Properties of Yolk‐Contaminated Egg Whites

Egg yolk contamination of egg whites continues to be a serious problem in the egg industry. The ability of egg whites to form stable and voluminous foams is greatly inhibited by yolk contamination, even at very low levels, between 0.01% and 0.2% w/w yolk in white. Experiments were conducted to determine if Mucor miehei lipase could regenerate the functional properties of yolk-contaminated egg whites. Lipase from M. miehei and colipase from porcine pancreas were added to yolk-contaminated (0.2%, w/w) egg white samples to hydrolyze triglycerides originating from egg yolk. Enzymatic hydrolysis of triacylglycerols was confirmed using thin-layer chromatography. Treatment of yolk-contaminated samples with lipase and colipase yielded significant (P < 0.05) improvements in a number of the functional properties, including the final foam volume, foam capacity, and foaming power. These functional properties showed complete restoration to control levels. However, foam stability and foam drainage levels were not statistically different from yolk-contaminated samples that had not been enzymatically treated. Enzyme-treated yolk-contaminated egg whites were also tested in angel food cakes. Enzyme-treated, yolk-contaminated egg whites performed similarly to non-yolk-contaminated control, and much better than yolk-contaminated sample in angel food cakes. The results show that most negative effects of yolk contamination can be reversed by treatment with Mucor miehei lipase and colipase.

Improving Foaming Properties of Yolk‐Contaminated Egg Albumen by Basic Soy Protein

Yolk contamination of egg white is a common problem in the egg breaking industry. Foaming properties of egg white protein are affected by such contamination, but proteins of basic nature may restore the foaming properties of the yolk-contaminated egg white protein. The purpose of this study was to chemically modify a soy protein, that is, to esterify the acidic groups on the protein and to study the potential of such modified protein in improving foaming. We showed that the modification changed the isoelectric point of soy protein isolate (SPI) from 4.5 to about 10. Sonication was proven to be a very effective means to redisperse the methanol-denatured soy protein during reaction, as shown by the improved solubility profile. Such modified basic protein, that is, the sonicated-modified SPI (SMSPI), when added to the yolk-contaminated (at 0.4% level, as-is basis) egg white, gave significantly improved foaming properties. We have shown that the slight change in pH due to the addition of SMSPI was not the reason for improved foaming performance; instead, the modified protein itself was the main reason for such improvement. Addition of SMSPI increased the foaming performance of both pure egg white and yolk-contaminated egg white. SMSPI consistently performed better than the unmodified SPI for improving foaming. Addition of SMSPI (16%, based on dry egg white, and 1.6% based on liquid egg white) fully restored foam expansion and foam liquid stability of 0.4% yolk-contaminated egg white, and it even out-performed the foaming of pure white protein. Therefore, a feasible solution to restore the foaming properties of yolk-contaminated egg white has been identified. It is expected that such modified SPI can be used as an additive or ingredient in foaming formulation, especially when the egg white protein is suspected of lipid contamination.

Effects of Yolk Contamination, Shearing, and Heating on Foaming Properties of Fresh Egg White

A series of experiments were conducted to evaluate effects of yolk contamination, shearing, and thermal treatment on foaming properties of liquid egg white. Samples obtained from industrial processing were also evaluated. Whipping and purging methods were both used to assess their effectiveness and sensitivity in evaluating foaming. A concentration as low as 0.022% (as-is basis) of yolk contamination caused significant reductions in foaming capacity and foaming speed. The neutral lipid fraction of egg yolk caused the major detrimental effect on foaming, and phospholipids fraction did not give significant foaming reduction at a concentration as high as 0.1%. High-speed and short-time shearing caused no apparent damage but longer shearing time significantly impaired foaming. Heat-induced foaming change is a function of temperature and holding time. Foaming was significantly reduced at a temperature of 55 degrees C for 10 min, whereas it did not change up to 3 min at a heating temperature of 62 to 64 degrees C. Industrial processing steps (pumping, pipe transfer, and storage) did not produce negative effects on foaming of the final products and the controlled pasteurization was actually beneficial for good foaming performance. Therefore, yolk contamination of the egg white was the major factor in reducing foaming properties of the white protein.

Deposition of Phage Type 4 and 13a Salmonella enteritidis Strains in the Yolk and Albumen of Eggs Laid by Experimentally Infected Hens

Because egg yolk and albumen differ substantially in their abilities to support bacterial growth, the initial level and location of Salmonella enteritidis deposition are critical for determining whether proposed standards for refrigerating eggs are likely to protect public health by preventing extensive microbial multiplication. In the present study, three groups of laying hens were infected with oral doses of approximately 10(9) cells of different S. enteritidis strains (two were phage type 4 and one was phage type 13a) in two replicate trials. For all three S. enteritidis strains, the incidence of yolk contamination (approximately 2.5% overall) was significantly greater than the incidence of albumen contamination (approximately 0.5% overall). The phage type 13a strain was less often isolated from fecal samples at 2 wk post-inoculation than were the phage type 4 strains, but no significant differences between strains were observed in the incidence of egg contamination. Most freshly laid contaminated eggs contained fewer than 1 S. enteritidis cell/ml of egg yolk or albumen, and no sample contained more than 67 S. enteritidis cells/ml.

Application of Chemical Methods to the Determination of Egg Yolk Contamination in Commercial Productions of Egg White Compared to Enzymatic Determination

Methods for lipid extraction and quantification by colorimetric determination of either ester or cholesterol were adapted to the measurement of egg yolk contamination in commercial egg white production. The resulting procedure was compared to enzymatic determination of egg yolk contamination in white. The procedure was applied to 23 productions of an egg processing plant. Contaminations ranged from 0.005 g/100 g to 0.4 g/100 g. Functional performance of the liquid egg white was best for productions with very low contamination. Productions with contaminations higher than 0.1 g/100 g showed substantial decrease of functional performance. There was no negative effect of yolk contamination on the flavour of spray-dried egg white.

The stability of the yolk granules of Artemia. An improved method for their isolation and study

The yolk granules of Artemia behave as unstable structures during isolation, especially after hatching. A stringent dechorionization of the cysts is required for an easy homogenization and good extraction of the yolk granules. The use of Ficoll and the avoidance of high dilutions in the homogenization process allows the isolation in an intact state of a pure yolk granules fraction without nuclear contamination. Previously described methods for the isolation of yolk granules lead to low recoveries of these structures in preparations with nuclear contamination. Lipovitellin, the major yolk protein, can be used as a biochemical marker to monitor the recovery of yolk granules and the possible yolk contamination of other subcellular fractions. The isolation of nuclei is also improved, their double membrane preserved in an enriched fraction with less yolk contamination than usually obtained with previously described methods. The other major storage structure, the lipoid bodies, can be isolated intact in these conditions, whereas they are also disrupted in common homogenization media.

Effect of Chemical Additives on Yolk-Contaminated Liquid Egg White

THE origin of the concept that chemical additives will improve the functional performance of yolk-contaminated egg white is vague. Koudele and Heinsohn (1960) credited Kothe (1953) with the discovery of a chemical additive to partially overcome the adverse effects of yolk contamination in egg white. The patent by Kothe (1953) concerned the use of a variety of ester-type organic chemicals, of which triethyl citrate was mentioned. It is conceivable that when an earlier patent, authored by Mink (1939) concerning the use of various anionic surface active compounds to improve the performance of egg white, was granted, chemical additives may have been used to improve yolk-contaminated egg white. However, specific effects on yolk-contaminated egg white were not mentioned in either of these patients or in other patents which concerned the use of chemical additives in egg whites (Littlefield, 1939; Werbin, 1952; Finucane and Mitchell, 1954; Jensen and Hale, 1954; Schaffer, 1956;…