Dileep A. Omana

Proteomic analysis of egg white proteins during storage.

Egg storage causes egg white to lose its viscous nature to form a thin liquid, commonly referred to as egg white thinning. To understand the mechanisms underlying egg white thinning, white‐shell eggs were used in the present study to determine the proteome‐level changes of egg white proteins occurred during storage. Egg white thinning was observed visually after 20 days of storage at ambient temperature (22±2°C) when the maximum number of proteome‐level changes occurred. The proteins that showed significant changes in abundance during storage included ovalbumin, clusterin, ovoinhibitor, ovotransferrin, and prostaglandin D2 synthase. Among these, only the abundance of clusterin was observed to change continuously during the storage period. Hence, it is expected that the increase in the concentrations of clusterin and ovoinhibitor along with the change of ovalbumin content during storage might contribute to egg white thinning. Degradation of ovalbumin/clusterin during egg storage may be due to the combined effect of proteolysis and increase in pH; this may also be partly responsible for egg white thinning phenomenon.

Co-extraction of egg white proteins using ion-exchange chromatography from ovomucin-removed egg whites

Efficient isolation of egg white components is desired due to its potential uses. Existing methods mainly targeted on one specific protein; an attempt has been made in the study to co-extract all the valuable egg white components in a continuous process. Ovomucin was first isolated by our newly developed two-step method; the resultant supernatant obtained after ovomucin isolation was used as the starting material for ion-exchange chromatography. Anion-exchange chromatography of 100 mM supernatant yielded a flow-through fraction and three other fractions representing ovotransferrin, ovalbumin and flavoproteins. The flow-through fraction was further separated into ovoinhibitor, lysozyme, ovotransferrin and an unidentified fraction which represents 4% of total egg white proteins. Chromatographic separation of 500 mM supernatant resulted in fractions representing lysozyme, ovotransferrin and ovalbumin. This co-extraction protocol represents a global recovery of 71.0% proteins.

The use of β-glucan as a partial salt replacer in high pressure processed chicken breast meat.

The effect of various ingredients such as sodium chloride (NaCl), sodium tripolyphosphate (STPP) and β-glucan (BG) on the biochemical properties of chicken breast proteins during temperature assisted high pressure processing was studied. Total protein solubility revealed that 600MPa pressure and 40(o)C are critical for the denaturation of proteins in STPP samples. Increase in reactive sulfhydryl groups with pressure indicate the exposure of buried sulfhydryl groups. Hydrophobicity and sulfhydryl contents revealed that hydrophobic interaction and disulphide bond formation are responsible for gel formation. The study revealed that 40(o)C and 400/600MPa pressure is optimum for high pressure processing of chicken breast meat. Addition of β-glucan with reduced NaCl and in the absence of sodium tripolyphosphate could produce gels with similar properties to those with 2.5% NaCl addition. Hence it is proposed that β-glucan can be used to reduce NaCl content of chicken products produced by temperature assisted high pressure processing.

Functional and rheological properties of proteins in frozen turkey breast meat with different ultimate pH

Functional and rheological properties of proteins from frozen turkey breast meat with different ultimate pH at 24 h postmortem (pH(24)) have been studied. Sixteen breast fillets from Hybrid Tom turkeys were initially selected based on lightness (L*) values for each color group (pale, normal, and dark), with a total of 48 breast fillets. Further selection of 8 breast samples was made within each class of meat according to the pH(24). The average L* and pH values of the samples were within the following range: pale (L* >52; pH ≤5.7), normal (46 < L* < 52; 5.9 < pH <6.1), and dark (L* <46; pH ≥6.3), referred to as low, normal, and high pH meat, respectively. Ultimate pH did not cause major changes in the emulsifying and foaming properties of the extracted sarcoplasmic and myofibrillar proteins. An SDS-PAGE profile of proteins from low and normal pH meat was similar, which revealed that the extent of protein denaturation was the same. Low pH meat had the lowest water-holding capacity compared with normal and high pH meat as shown by the increase in cooking loss, which can be explained by factors other than protein denaturation. Gel strength analysis and folding test revealed that gel-forming ability was better for high pH meat compared with low and normal pH meat.Dynamic viscoelastic behavior showed that myosin denaturation temperature was independent of pH(24). Normal and high pH meat had similar hardness, springiness, and chewiness values as revealed by texture profile analysis. The results from this study indicate that high pH meat had similar or better functional properties than normal pH meat. Therefore, high pH meat is suitable for further processed products, whereas low pH meat may need additional treatment or ingredient formulations to improve its functionality.

Proteomics Analysis of Egg White Proteins from Different Egg Varieties

The market of specialty eggs, such as omega-3-enriched eggs, organic eggs, and free-range eggs, is continuously growing. The nutritional composition of egg yolk can be manipulated by feed diet; however, it is not known if there is any difference in the composition of egg white proteins among different egg varieties. The purpose of the study was to compare the egg white proteins among six different egg varieties using proteomics analysis. Egg white proteins were analyzed using two-dimensional gel electrophoresis (2-DE), and 89 protein spots were subjected to LC-MS/MS. A total of 23 proteins, belonging to Gallus gallus , were identified from 72 detected protein spots. A quiescence-specific protein precursor in egg white was identified for the first time in this study. Significant differences in the abundant levels of 19 proteins (from 65 protein spots) were observed among six egg varieties. Four proteins, ovalbumin-related protein Y, cystatin, avidin, and albumin precursor, were not different among these six egg varieties. These findings suggest that the abundance, but not the composition, of egg white proteins varied among the egg varieties.

Alkali-aided protein extraction of chicken dark meat: Composition and stability to lipid oxidation of the recovered proteins

Chicken dark meat has been considered as a major underused commodity due to the increasing demand for further-processed breast meat products. One option to increase the utilization of chicken dark meat is to extract myofibrillar proteins and separate them from fat and pigments to enhance their application for the preparation of further-processed meat products. The objective of the current study was to determine the effect of pH, in the range of 10.5 to 12.0, on the alkaline solubilization process of chicken dark meat. Aspects studied were the effect of the alkali-aided process on protein content, lipid composition, lipid oxidation, and color characteristics of the extracted meat. Each experiment and each assay were done at least in triplicate. Lipid content of the extracted meat showed a 50% reduction compared with the chicken dark meat. Neutral lipids were reduced by 61.51%, whereas polar lipids were not affected by the alkali treatments. There was a higher amount of TBA reactive substances observed in the extracted meat compared with chicken dark meat, indicating that extracted meat was more susceptible to oxidation. Long-chain polyunsaturated fatty acids (22:4n-6, 20:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3), which were detected only in the polar lipids, were responsible for increasing lipid oxidation susceptibility of extracted meat compared with chicken dark meat. Alkali-aided extraction of chicken dark meat lightened the color of the meat. The redness, yellowness, and total heme pigments in extracted meat significantly decreased by 83, 11, and 53%, respectively, compared with chicken dark meat. Even though this process did not remove polar lipids, based on our early findings, the extracted meat had considerable physicochemical and textural properties for product preparation compared with those of raw dark meat. Hence, alkali recovery of protein can be considered a potentially useful method to increase the utilization of dark chicken meat.

Impact of citric acid and calcium ions on acid solubilization of mechanically separated turkey meat: Effect on lipid and pigment content

Increased demand for poultry products has resulted in an increased availability of by-products, such as the neck, back, and frame, that can be processed into mechanically separated poultry meat. The major problems with mechanically separated poultry meat are its high lipid content, color instability, and high susceptibility to lipid oxidation. The present work was undertaken to determine the effect of different concentrations of citric acid and calcium ions on protein yield, color characteristics, and lipid removal from protein isolates prepared using an acid-aided extraction process. Six levels of citric acid (0, 2, 4, 6, 8, and 10 mmol/L) and 2 levels of calcium chloride (0 and 8 mmol/L) were examined. The entire experiment was replicated 3 times, resulting in 36 extractions (3 × 6 × 2). The highest (P < 0.05) protein yield was found for the treatment with 6 mmol/L of citric acid. In general, all the combinations removed an average of 90.8% of the total lipids from mechanically separated turkey meat, ranging from 86.2 to 94.7%. The lowest amount (1.14%) of total lipids obtained was for samples treated with 4 mmol/L of citric acid. Maximum removal of neutral lipids (96.5%) and polar lipids (96.4%) was attained with the addition of 6 and 2 mmol/L of citric acid, respectively. Polar lipid content was found to be significantly (P = 0.0045) affected by the presence of calcium chloride. The isolated proteins were less (P < 0.05) susceptible to lipid oxidation compared with raw mechanically separated turkey meat. The most efficient removal of total heme pigment was obtained with the addition of 6 or 8 mmol/L of citric acid. Addition of calcium chloride had a negative effect on total pigment content. The study revealed that acid extractions with the addition of citric acid resulted in substantial removal of lipids and pigments from mechanically separated turkey meat, improved stability of the recovered proteins against lipid oxidation, and appreciable protein recovery yields.

Evaluation of poultry protein isolate as a food ingredient: Physicochemical characteristics of low-fat turkey bologna

Evaluation of poultry protein isolate (PPI) as a food ingredient was carried out by substituting nonmeat ingredients such as soy protein isolate (SPI) or meat protein in turkey bologna. Two concentrations (1.5 and 2% dry weight basis) of PPI prepared from mechanically separated turkey meat were used in this study. Two control samples were prepared with 11 and 13% meat protein, respectively. Physicochemical characteristics of turkey bologna containing PPI were compared with those of control and SPI-containing samples. Batter strength was higher for 2% PPI and 13% meat protein control samples (control-2) compared with all other treatments. Cooking yield of the 11% meat protein control was significantly (P < 0.05) less compared with other treatments. However, there was no significant difference in the expressible moisture or purge loss among all the treatments. Control-2 showed lower L* values and was more reddish during refrigerated storage. Addition of protein isolates caused a significant increase (b* value varied between 11.48 and 12.52) in yellowness of products. Turkey bologna with added protein isolates showed significantly lower lipid oxidation as indicated by induced TBA reactive substance analysis. Results from this study suggest that SPI or meat protein could be replaced by PPI without negatively affecting product characteristics as evident from cooking yield and purge loss values.

Use of Poultry Protein Isolate As a Food Ingredient: Sensory and Color Characteristics of Low-Fat Turkey Bologna

UNLABELLED The potential of using poultry protein isolate (PPI) as a food ingredient to substitute either soy protein isolate (SPI) or meat protein in turkey bologna was investigated. PPI was prepared from mechanically separated turkey meat using pH-shift technology and the prepared PPI was added to turkey bologna at 2 different concentrations (1.5% and 2% dry weight basis). Product characteristics were compared with those prepared with the addition of 2% SPI, 11% meat protein (control-1), or 13% meat protein (control-2). All the 5 treatments were subjected to sensory analysis to evaluate aroma, appearance, color, flavor, saltiness, juiciness, firmness, and overall acceptability of the turkey bologna samples using 9-point hedonic scales. A turkey bologna control sample with 11% meat protein appeared to be softer compared to other treatments as revealed by texture profile analysis while purge loss during storage in a retail display case was significantly (P < 0.05) higher compared to other treatments. Lightness (L*) value of the products decreased during 4 wk of retail storage. A turkey bologna control sample with 13% meat protein appeared to be darker and more reddish compared to other treatments. Replacing meat protein with protein isolates caused increase in yellowish color of turkey bologna. Sensory analysis concluded that 1.5% PPI and 2% PPI could be used as substitute of SPI or lean meat and the treatments could be improved by increasing saltiness and decreasing firmness. PRACTICAL APPLICATION The study revealed that with slight modifications in saltiness, turkey bologna can be prepared with the addition of poultry protein isolates as an acceptable substitute for soy protein isolate or meat protein. This will help to avoid usage of nonmeat ingredients (as SPI substitute) and to reduce the cost of production (as meat protein substitute) of low-fat turkey bologna.

Evaluation of Poultry Protein Isolate as a Food Ingredient: Physicochemical Properties and Sensory Characteristics of Marinated Chicken Breasts

The possibilities of replacing soy protein isolate (SPI) and reducing the amount of phosphate in marinated chicken breasts using poultry protein isolate (PPI) were investigated. PPI, prepared from mechanically separated turkey meat through the pH-shift technology, was used as a marinade ingredient for chicken breasts at 2 different concentrations (1.0% and 1.5%, w/w on a dry weight basis). Product characteristics were compared to samples marinated with salt, phosphate, or SPI. All the 5 treatments were subjected to instrumental and sensory analyses. Tumbling yield, drip, and cooking losses as well as expressible moisture showed that PPI can be used as a substitute for SPI in brine. The sensory analysis revealed that there were no differences among treatments in terms of appearance, color, flavor, saltiness, juiciness, tenderness, and overall acceptability of the marinated chicken breasts. However, chicken breasts marinated with phosphate had significantly higher aroma acceptability scores than those treated with 1% PPI.