Influence of on-farm production practices on sensory and technological quality characteristics of pork loin.

Quality of pork from pigs raised either traditionally (outdoor access or bedded settings with no sub-therapeutic antibiotics or growth promotants in feed) or conventionally (commercial indoor) was evaluated. Pork loins (m. longissimus thoracis et lumborum, LTL) from four hundred pigs from either traditional or conventional production systems (n=200) fed commercially formulated diets ad libitum were harvested at slaughter. Intramuscular crude fat content and lean color (L* and b*) values were significantly decreased in conventional pork loins. LTL from conventionally-raised pig carcasses showed increased (P<0.05) mean pH, moisture content and reduced cooking loss and shear force values and had increased tenderness and juiciness scores compared to those from traditionally-raised pig carcasses. Results indicated that pork from conventionally raised pigs was superior to that from traditionally raised pigs in terms of tenderness and juiciness, suggesting that consumers may value pork from traditionally raised pigs on the basis of factors other than eating quality and appearance.

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.

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.

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.

Alkali-aided protein extraction from chicken dark meat: textural properties and color characteristics of recovered proteins.

Textural properties, water-holding capacity, and color characteristics of alkali-extracted chicken dark meat have been studied. Alkali extraction was carried out at 4 different pH values (10.5, 11.0, 11.5, and 12.0). At higher pH of extraction, cooking loss and water loss were found to be significantly decreased (P < 0.05). The lightness (L* value) of the recovered samples treated at higher pH was found to be significantly lower (P < 0.05). Whiteness of uncooked samples also decreased significantly at higher extraction pH values. Protein samples extracted at higher pH values were found to be harder, and the maximum (4,956 g of force) value was shown by samples prepared at pH 11.5. Chewiness values were significantly increased (P < 0.05) for protein samples extracted at pH values of 11.5 and 12.0. Dynamic viscoelastic behavior of samples was assessed in the temperature range of 7 to 100 degrees C. The dynamic viscoelastic behavior of raw chicken dark meat as revealed by storage modulus indicated considerable gel-forming ability. The maximum storage modulus (G') value of 439 kPa was measured at 66.7 degrees C. Storage modulus was found to decrease for the recovered protein samples and be lowest at higher pH values. However, the recovered protein samples did show substantial gel-forming ability when stored with cryoprotectants. Tan delta values denoted 2 clear transitions for raw dark meat; however, only 1 major transition at 50.1 degrees C was evident for pH-treated samples, probably reflecting the loss of collagen in processing. In conclusion, this process of protein recovery may offer the possibility to use the underused poultry resources for preparation of functional foods.

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.

Effect of different concentrations of calcium chloride and potassium chloride on egg white proteins during isoelectric precipitation of ovomucin.

The effect of various concentrations of CaCl2 and KCl on egg white proteins during isoelectric precipitation of ovomucin was investigated in this study. At low concentrations of CaCl2 (<50 mM), lysozyme was the major contaminant in the precipitated ovomucin, whereas ovalbumin was the predominant one at high concentrations (>or=100 mM). At 50 mM CaCl2 concentration, the concentrations of both lysozyme and ovalbumin were moderate. Ovomucin with a purity of 97.3% was prepared using a 2-step method: egg white was first precipitated in the presence of 50 mM CaCl2 followed by a second 500 mM CaCl2 extraction. The concentrations of other proteins in the precipitate were 1.3% of ovalbumin, 1.1% of lysozyme, and 0.4% of ovomucoid. Unlike CaCl2-treated samples, ovotransferrin was found to be the second major contaminant in all KCl-treated precipitates. Compared with the control, adding KCl at the lowest concentration of 2.5 mM increased significantly the content of ovalbumin (from 7.6 to 68.0%) and reduced significantly the content of lysozyme (from 25.5 to 6.4%) in the precipitates; however, increasing the concentrations of KCl up to 500 mM did not affect the content of ovalbumin, but the content of lysozyme showed a general reduction trend. Although KCl was used widely in literature as the last step of ovomucin washing, our results show that KCl is not an efficient salt in purifying ovomucin.