K. C. Nam

A simple and efficient method for preparing partially purified phosvitin from egg yolk using ethanol and salts.

The objective of this study was to develop a new protocol that could be used for large-scale separation of phosvitin from egg yolk using ethanol and salts. Yolk granules, which contain phosvitin, were precipitated after diluting egg yolk with 9 volumes of distilled water. The pH of the yolk solution was adjusted to pH 4.0 to 8.0 using 6 N HCl or NaOH, and then yolk granules containing phosvitin was separated by centrifugation at 3,220 × g for 30 min. Lipids and phospholipids were removed from the insoluble yolk granules using 85% ethanol. The optimal volumes and concentration of ethanol in removing lipids from the precipitants were determined. After centrifugation, the lipid-free precipitants were homogenized with 9 volumes of ammonium sulfate [(NH(4))(2)SO(4)] or NaCl to extract phosvitin. The optimal pH and concentration of (NH(4))(2)SO(4) or NaCl for the highest recovery rate and purity for phosvitin in final solution were determined. At pH 6.0, all the phosvitin in diluted egg yolk solution was precipitated. Among the (NH(4))(2)SO(4) and NaCl conditions tested, 10% (NH(4))(2)SO(4) or 10% NaCl at pH 4.0 yielded the greatest phosvitin extraction from the lipid-free precipitants. The recovery rates of phosvitin using (NH(4))(2)SO(4) and NaCl were 72 and 97%, respectively, and their purity was approximately 85%. Salt was removed from the extract using ultrafiltration. The salt-free phosvitin solution was concentrated using ultrafiltration, the impurities were removed by centrifugation, and the resulting solution was freeze-dried. The partially purified phosvitin was suitable for human use because ethanol was the only solvent used to remove lipids, (NH(4))(2)SO(4) or NaCl was used to extract phosvitin, and ultrafiltration was used to remove salt and concentrate the extract. The developed method was simple and suitable for a large-scale preparation of partially purified phosvitin.

Factors Affecting Cooked Chicken Meat Flavour: A Review

Flavour, one of the most important factors affecting consumers meat-buying behaviour and preferences, comprises mainly of taste and aroma. The cooked meat flavour, that is important from the producer and consumer point of view, is affected by several pre- and post-slaughter factors, including breed, diet, post-mortem ageing, and method of cooking. Moreover, chicken meat is prone to the development of off-flavours through lipid oxidation, which reduce the quality of the chicken meat. The aim of this review is to discuss the main factors affecting cooked chicken meat flavour which helps producers and consumers to produce the most flavoured and consistent product possible. Cooked chicken meat flavour is thermally derived via the Maillard reaction, the degradation of lipids, and interaction between these two reactions. Factors affecting the flavour of cooked chicken meat were identified as breed/strain of the chicken, diet of the bird, presence of free amino acids and nucleotides, irradiation, high pressure treatment, cooking, antioxidants, pH, and ageing.

Enzymatic hydrolysis of ovalbumin and the functional properties of the hydrolysates

Ovalbumin is the predominant protein in egg white and is widely used in cell culture. However, it also can be used to produce peptides with various functional properties. The objectives of this study were to hydrolyze ovalbumin using various enzyme, incubation time, and temperature combinations, and to compare the functional properties of the hydrolysates. Ovalbumin (20 mg/mL) was hydrolyzed with 1% of pepsin, trypsin, α-chymotrypsin, papain, and alcalase, singly or in combination at 37°C, and then the enzymes were inactivated at 100°C for 15 min. Hydrolyzing ovalbumin with pepsin (OAPe), pepsin + papain (OAPePa), pepsin + alcalase (OAPeAl), alcalase + trypsin (OAAlTr), and α-chymotrypsin (OACh) was also effective in producing peptides from ovalbumin, and the peptides produced had strong iron- and copper-binding capacities and antioxidant capability. However, the best treatment of all was the OAAlTr treatment, which showed the highest iron-chelating and antioxidant activities among the enzyme treatments (P < 0.05). Electrospray-ionization mass spectrometry (MS/MS) analysis identified numerous peptides (<5 kDa) from the OAPe, OAPeAl, OACh, OAAlTr, and OAPePa hydrolysates of ovalbumin, but the number and size of peptides varied widely depending on the treatments. The enzymatic hydrolysis significantly increased the functionality of ovalbumin, and the improvement depended upon the composition of peptides produced rather than the number of the peptides produced.

Effects of chitosan coating and storage with dry ice on the freshness and quality of eggs

To develop a method that can maintain egg freshness during practical storage conditions, eggs were coated with chitosan and stored with or without dry ice. The physicochemical and microbiological qualities of eggs were evaluated during 14 d of storage at 4 and 23°C without dry ice and at 23°C with dry ice. The combination of chitosan coating and dry ice significantly inhibited a Haugh unit decrease during storage at 23 °C. No difference in functional properties, such as foaming ability, foam stability, and viscosity, among treatments was observed, but chitosan coating and storage with dry ice decreased the rate of pH increase and moisture loss in albumen at d 7 and 14. The eggs treated with chitosan coating and storage with dry ice had a significantly lower number of Salmonella Typhimurium inoculated on the egg surface than did control eggs during storage at 23°C. Results revealed that the combination of chitosan coating and storage with dry ice limited the moisture loss, CO(2) emission, and pH increase, which helped maintaining the freshness of eggs. Microbial growth was also inhibited during storage at 23°C.

The functional property of egg yolk phosvitin as a melanogenesis inhibitor.

Phosvitin is a phosphoglycoprotein present in egg yolk. More than half of the amino acids in phosvitin molecule are serine, of which >90% are phosphorylated. Therefore, phosvitin has a strong metal binding capability. The aim of this study was to investigate the effect of phosvitin on the inhibition of melanogenesis in melanoma cells. The results showed that phosvitin inhibited the activity of mushroom tyrosinase. Addition of phosvitin at a concentration of 50μg/ml, to B16F10 melanoma cells inhibited tyrosinase activity by approximately 42% and melanin synthesis by 17% compared to those in a control without phosvitin. Phosvitin inhibited the expression of tyrosinase, tyrosinase-related protein 1 (TRP-1), TRP-2, and microphthalmia-associated transcription factor (MITF) in B16F10 melanoma cells. In addition, phosvitin reduced the cellular cAMP concentration in B16F10 melanoma cells. These results indicate that phosvitin has the potential to be used as a melanogenesis inhibitor in the food and cosmetics industry.

Dose-Dependent Changes of Chemical Attributes in Irradiated Sausages

To determine the effects of irradiation on the chemical attributes of sausages, TBARS values, volatile compounds, gaseous compounds, and hydrocarbons of vacuum-packaged sausages were analyzed during 60 d of refrigerated storage. A sulfur-containing volatile (dimethyl disulfide), a gas (methane), and radiation-induced hydrocarbons (1-tetradecene, pentadecane, heptadecane, 8-heptadecene, eicosane, 1, 7-hexadecadiene, hexadecane) were mainly detected in irradiated sausages and the concentrations of these compounds were irradiation dose-dependent with R(2) = 0.9585, 0.9431, and 0.9091-0.9977, respectively. Especially methane and a few hydrocarbons were detected only in irradiated sausages and their amounts were dose-dependent. On the other hand, TBARS values, other off-odor volatiles (carbon disulfide, hexanal), and gases (carbon monoxide, carbon dioxide) were found both in irradiated and nonirradiated sausages. Therefore, it is suggested that radiation-induced hydrocarbons (1-tetradecene, pentadecane, heptadecane, 8-heptadecene, eicosane, 1, 7-hexadecadiene, hexadecane), dimethyl disulfide, and methane can be used as markers for irradiated sausages.

Effect of dietary supplementation of gallic acid and linoleic acid mixture or their synthetic salt on egg quality.

The effect of a dietary supplementation of gallic acid and linoleic acid mixture (MGL) and their synthetic salt, sodium 2,3-dihydroxy-5-(((9E,12E)-octadeca-9,12-dienyloxy)carbonyl)phenolate (NGL), on egg quality was investigated. A total of 120 laying hens were allotted into five groups over 4weeks of the experimental period. Birds were fed the following diets: (1) control [commercial diet (CD)], (2) 0.05% MGL (w/w, GA:LA=1:1, equal molar ratio), (3) 0.1% MGL, (4) 0.05% NGL, (5) 0.1% NGL. The performance of the hen, the anti-oxidative potential of egg albumen and yolk, and the fatty acid composition and cholesterol content of egg yolk were measured. The TBARS value of egg yolk from hens fed 0.1% MGL and 0.05% NGL was lower than that fed control diet after storage for 14days. The ABTS(+) reducing activity of egg albumen was significantly improved by MGL and NGL, but only NGL had an effect on yolk (p<0.05). The dietary supplementation of 0.05% or 0.1% MGL, and 0.05% NGL raised the PUFAs composition in egg yolk. The cholesterol content of egg yolk from hens fed control diet was higher than those fed 0.1% MGL, 0.05% or 0.1% NGL (p<0.05). In conclusion, a diet consisting of MGL and NGL can improve the antioxidative potential of egg and the fatty acid quality of egg yolk while lowering the cholesterol level.

Effect of garlic, onion, and their combination on the quality and sensory characteristics of irradiated raw ground beef.

Irradiated raw ground beef had lower a*- and b*-values than nonirradiated ones regardless of garlic or onion treatment at 0 d. Irradiation increased TBARS values of control ground beef, but addition of 0.5% onion or 0.1% garlic+0.5% onion reduced oxidative changes during storage. Addition of garlic or onion greatly increased the amounts of sulfur compounds, but the increase was greater with garlic. With irradiation, the profiles and amounts of S-volatiles in raw ground beef changed significantly. However, the intensity of irradiation aroma in irradiated raw ground beef with garlic or onion was similar to that of the nonirradiated control. This indicated that some of the sulfur compounds unique to garlic or onion interacted with common sulfur compounds detected in irradiated meat and masked or changed the odor characteristics of irradiated raw ground beef. It was concluded that >0.5% onion or <0.01% garlic would be needed to mask or prevent irradiation aroma in irradiated raw ground beef.

Comparison and Correlation Analysis of Different Swine Breeds Meat Quality

This study was performed to determine the influence of pig breed and gender on the ultimate pH and physicochemical properties of pork. The correlations between pH and pork quality traits directly related to carcass grade, and consumer’s preference were also evaluated. The pH and meat grading scores for cold carcasses of 215 purebred pigs (Duroc, Landrace, and Yorkshire) from four different farms were obtained. Meat quality parameters of the pork loin were analyzed. Duroc and female animals were more affected compared to other breeds and male pigs. Duroc animals had the highest ultimate pH, carcass back fat thickness, marbling scores, yellowness, and fat content (p<0.05). Landrace pigs had the highest color lightness and cooking loss values (p<0.05). Among all trait parameters, marbling scores showed the highest significant differences when evaluating the impact of breed and gender on meat quality characteristics (p<0.001). Ultimate pH was positively correlated with carcass weight (0.20), back fat thickness (0.19), marbling score (0.17), and color score (0.16) while negatively correlated with cooking loss (−0.24) and shear force (−0.20). Therefore, pork samples with lower ultimate pH had lower cooking loss, higher lightness, and higher shear force values irrespective of breed.

Evaluation of radiation-induced compounds in irradiated raw or cooked chicken meat during storage

The concentrations of hydrocarbons, 2-alkylcyclobutanones, and sulfur volatiles in irradiated (0 and 5 kGy) chicken meat samples (raw, precooked, and irradiated-cooked) were analyzed after 0 and 6 mo of frozen storage (-40°C) under oxygen-permeable packaging conditions. Two hydrocarbons [8-heptadecene (C(17:1)) and 6,9-heptadecadiene (C(17:2))], two 2-alkylcyclobutanones (2-dodecylcyclobutanone and 2-tetradecylcyclobutanone), and dimethyl disulfide were determined as radiation-induced detection markers in the irradiated raw and cooked chicken meats. Although irradiated-cooked samples produced fewer hydrocarbons and 2-alkylcyclobutanones than precooked irradiated samples, the number of individual hydrocarbons or 2-alkylcyclobutanones was still sufficient to detect radiation treatment even after 6 mo of storage at -40°C. Among sulfur volatiles, only dimethyl disulfide was found in meat after 6 mo of storage, indicating it has potential to be used an irradiation detection marker for frozen-stored meats under oxygen-permeable packaging conditions.