Analytical Method for Differentiation of Chilled and Frozen-Thawed Chicken Meat
Abstract : Chilled and frozen chicken breast and thigh meat were stored at +4±1 oC and - 20±1 oC, respectively. Maillard reaction between ribose and meat proteins of the chicken samples was initiated. The changes in the ribose-induced Maillard reaction rate during chilled and frozen storage of chicken meat were evaluated on the bases of corrected absorbance values (A420*) and bovine melanoidin equivalent values (mg BME/g). Application of BME as a measure of ribose-induced Maillard reaction rate enables comparability of the data obtained by different spectrophotometers. It was found that the BME values of chicken meat frozen stored for more than 15 days were significantly (P<0.05) lower than BME values of chilled-stored samples. According to the suggested threshold limit values the chicken thigh and breast meat with BME values lower than 30 mg BME/g and 51 mg BME/g, respectively could be classified as frozen-thawed.
Ribose-induced Maillard Reaction as an Analytical Method for Detection of Adulteration and Differentiation of Chilled and Frozen-thawed Minced Veal
Abstract Quality control of meat products is one of the main concerns of consumers, governmental control authorities, and retailers. The purpose of this study was to employ ribose-induced Maillard reaction in detection of meat adulteration and differentiation of fresh-chilled from frozen-thawed minced veal. The browning intensity was assessed through measuring the absorbance at 420 nm with a spectrophotometer as well as the direct analysis of the color and pH. The results showed that CIE b*, CIE a*, and A420* values in the extract of fresh-chilled veal were significantly (p<0.05) higher than frozen-thawed samples. The extract of frozen meat samples stored at −18°C became significantly darker and more yellowish compared to −4°C. The results showed that the A420* value in the frozen-thawed veal stored at −4°C and −18°C was reduced by approximately 17.22±3.53% and 11.68±2.49%, respectively, compared with fresh-chilled veal. The findings also showed that the storage temperature of minced veal and the heating time in this reaction had a significant effect on all tested variables (p<0.0001). The proposed method can be considered as an easy, quick, and inexpensive test for differentiating between the fresh-chilled and frozen-thawed minced veal.
Chemical, physical, and functional properties of oxidized turkey white muscle myofibrillar proteins
Oxidative damage to turkey white muscle myofibrillar proteins (MP) was investigated by measuring changes in chemical, physical, and functional properties after exposure to iron or copper (25 micromolar) and ascorbate. Both iron- and copper-oxidized MP exhibited increased absorbance at 265 nm and carbonyl content compared to controls. Increasing the ascorbate concentration from 0 to 25 millimole increased the absorbance 6.8- and 4.0-fold and the carbonyl content 2.6- and 1.9-fold for MP in the presence of iron and copper, respectively. The iron- and copper-oxidized MP showed lower solubility, gel strength, and gel water-holding capacity than controls. SDS-polyacrylamide gel electrophoresis demonstrated that both iron- and copper-catalyzed oxidation resulted in a major loss of myosin and actin with concomitant formation of protein polymers. These data suggest that the decreased functionality of proteins in muscle foods exposed to oxidative environments could be due to chemical and physical changes resulting from oxidative reactions.