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.

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.

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.

The use of ß-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 ß-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 ß-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 ß-glucan can be used to reduce NaCl content of chicken products produced by temperature assisted high pressure processing.

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.

Effect of acid- and alkaline-aided extractions on functional and rheological properties of proteins recovered from mechanically separated turkey meat (MSTM).

UNLABELLED: Functional and rheological characteristics of acid- and alkali-extracted proteins from mechanically separated turkey meat (MSTM) have been investigated. Extractions were carried out at 4 pH values (2.5, 3.5, 10.5, and 11.5). The study demonstrated that alkali and acid extractions resulted in significant (P < 0.0001) decreases of cooking and water loss compared to raw MSTM; however, the cooking loss was found to be similar (P = 0.5699) among the different protein isolates. Proteins extracted at pH 10.5 showed the lowest (P = 0.0249) water loss. Emulsion and foaming properties were found to be slightly higher in alkali-extracted proteins compared to those for acid extractions. The myofibrillar protein fraction showed better ability to form and stabilize emulsions compared to sarcoplasmic proteins. Myofibrillar proteins also showed better foam expansion; however, foam volume stability was similar for both myofibrillar and sarcoplasmic protein fractions. Textural characteristics (hardness, chewiness, springiness, and cohesiveness) of recovered proteins were found to be unaffected (P > 0.05) by different extraction pH. The protein extracted at pH 3.5 formed a highly viscoelastic gel network as evidenced by storage modulus (G') values, whereas the gel formed from proteins extracted at pH 10.5 was found to be the weakest. The work also revealed that acid treatments were more effective for removal of total heme pigments from MSTM. Color characteristics of protein isolates were markedly improved compared to the initial material and tended to be better when subjected to acid extractions. PRACTICAL APPLICATION: Mechanically separated meat is one of the cheapest sources of protein obtained by grinding meat and bones together and forcing the mixture through a perforated drum. The use of mechanically separated turkey meat (MSTM) for the production of further processed poultry products is limited due to its undesirable color and textural properties. Recovery of proteins from MSTM using pH shifting process will help the poultry processors to get better returns and also create opportunity to produce functional food ingredients.

Ovomucin - a glycoprotein with promising potential.

Ovomucin, accounting for ∼3.5% of total egg white protein, is responsible for the thick gel characteristics of liquid egg white. Besides its excellent foaming and emulsion capacities, it possesses anti-viral, anti-bacterial, anti-tumor and other bioactivities. This paper reviews compositional, structural, physicochemical, functional and biological properties of ovomucin, as well as development of methods of extraction. As one of the least defined proteins in egg white, further study is required to characterize the structure and to explore its full potential in new applications as functional foods and nutraceuticals.

A new method of separating ovomucin from egg white.

Ovomucin, a key component in maintaining the viscous nature of egg white, is a glycoprotein contributing to 2-4% of the total egg albumin protein. Preparation of pure ovomucin remains a challenge due to the presence of coprecipitated proteins, mainly ovalbumin and lysozyme. The objectives of the study were to determine the effect of different salt concentrations on the extractability of ovomucin and to develop a simple method to purify ovomucin that could be adapted for further scale-up production. The protein compositions of ovomucin extracts were significantly affected by salt concentrations. The concentration of ovalbumin was increased, whereas that of lysozyme was decreased in the ovomucin extracts at increasing salt concentrations up to 500 mM; lysozyme was the major contaminant at low salt concentrations (<100 mM), whereas ovalbumin was the major contaminant at high concentrations (>or=200 mM). A 2-step method was developed for the first time to prepare ovomucin with a purity of greater than 90%. Egg white was first extracted in the presence of 100 mM NaCl at pH 6.0 to produce a precipitate containing moderate coprecipitated ovalbumin (14.6%) and lysozyme (15.9%); the contaminated proteins in the precipitate were further removed by using 500 mM NaCl. The yield of ovomucin was determined to be 400.2 mg/100 g of egg white. This 2-step method is simple, environmentally friendly, and easy for scale-up preparation.