Meat Science

Thirty-two Merino lambs fed barley straw and a concentrate alone (CONTROL) or enriched with vitamin E (VITE006) or carnosic acid (CARN006; CARN012) were used to assess the effect of these antioxidant compounds on meat quality attributes. The animals were slaughtered after being fed for at least 5weeks with the experimental diets. The longissimus lumborum samples of VITE006, CARN006 and CARN012 groups showed higher values (P<0.001) of L* (lightness) through the complete storage period under modified atmosphere when compared to the CONTROL group. Moreover, the VITE006 and CARN012 samples revealed lower discoloration when compared to the CONTROL group, these differences being more apparent in a less color stable muscle such as gluteus medius (P<0.05 for hue after 14days of refrigerated storage). Meat sensory traits were not significantly affected by carnosic acid and microbiological analyses were not conclusive at the doses administered.

Thirty-two Merino lambs fed barley straw and a concentrate formulated either with palm oil (CTRL group) plus quercetin (QCT group) or flaxseed (FS group) plus quercetin (FS-QCT group) were used to assess the effects of this flavonoid on meat quality attributes. The animals were slaughtered after being fed for at least 5weeks with the experimental diets. Chemical composition of longissimus thoracis (LT) muscle was not different among treatments. The longissimus lumborum (LL) samples of QCT and FS-QCT groups revealed lower discolouration (hue angle) when compared to the CTRL and FS lambs (P<0.05), whereas extract release volume (ERV) and microbiological data jointly suggest that flaxseed and quercetin may reduce the growth of microbial populations responsible for meat spoilage in quadriceps femoris (QF).

Case-ready fresh beef is typically packaged in a modified-atmosphere with approximately 80% oxygen and 20% carbon dioxide. Recently, USDA approved distribution of fresh meats in a master bag system using 0.4% carbon monoxide (CO). This study compared effects of packaging system (vacuum, 80% oxygen, 0.4% carbon monoxide), fresh meat storage time (7-21 days) and cooking temperature (49-79 °C) on extent of myoglobin denaturation, color and rancidity in cooked top sirloin steaks. Steaks packaged in 80% oxygen or CO retained desirable red color for 14 and 21 days storage, respectively. Steaks stored in 80% oxygen exhibited the greatest TBA values and myoglobin denaturation at all storage times and cooking temperatures. Steaks stored in high oxygen developed brown interior color at internal temperatures as low as 57 °C, the premature browning effect. Premature browning and rancidity associated with steaks packaged in 80% oxygen was prevented by packaging in 0.4% CO or vacuum.

Changes in the ultrastructure of myofibrillar protein as a result of 1,5-glucono-δ-lactone-induced gelation at chilled temperatures were investigated using transmission electron microscopy. The myofibril structure appeared to have completely disintegrated at pH 4.0 resulting in a granular, amorphous appearance. It was suggested that as the pH was lowered to about 4.5, partial extraction of the A-band proteins occurred. A composite system of a myosin gel network reinforced by the residual myofibrillar structure was proposed to have formed. As the pH was lowered further, complete depolymerisation of actomyosin was suggested to have resulted in the formation of a predominantly myosin gel. The inclusion of sodium chloride resulted in swelling of the myofibrillar protein and retention of the myofibrillar structure to pH 3.8.

The effects of salt level and high pressure processing on cook loss, emulsion stability, colour, textural and sensory characteristics of frankfurters were investigated. Two salt levels (1.5 and 2.5%) and two pressure treatments (150 and 300 MPa) were examined. For each batch a control was set up which was non-pressure treated. Cook loss values were significantly decreased in 150 MPa products at the 2.5% salt level compared to controls. Significantly lower cook losses were recorded at the lower salt level after the application of 150 MPa pressure. The stability of the meat emulsions was significantly increased at the lower salt level, especially after 150 MPa pressure. Sensory analysis results for overall flavour acceptability after pressure application of 150 MPa and 300 MPa were similar to control products and panellists preferred products formulated at 1.5% salt after pressure treatment (150 MPa). Hardness, cohesiveness, gumminess and chewiness were also improved after pressure treatment. The results demonstrate that high pressure technology is a viable process that partially compensates for the reduction of salt levels in frankfurters.

Meat tenderness is an important characteristic in terms of consumer preference and satisfaction. However, each consumer may have his/her own criteria to judge meat tenderness, because consumers are neither selected nor trained like an expert sensory panel. This study aimed to characterize consumer tenderness using descriptive texture profiles such as chewiness and hardness assessed by a trained panel. Longissimus muscles cooked at four different end-point temperatures were subjected to a trained sensory panel (n=18) and consumer (n=107) tenderness tests. Multiple regression analysis showed that consumer tenderness was characterized as 'low-chewiness and low hardness texture.' Subsequently, consumers were divided into two groups by cluster analysis according to tenderness perceptions in each participant, and the two groups were characterized as 'tenderness is mainly low-chewiness' and 'tenderness is mainly low-hardness' for tenderness perception, respectively. These results demonstrate objective characteristics and variability of consumer meat tenderness, and provide new information regarding the evaluation and management of meat tenderness for meat manufacturers.

Investigations have been made into possible spectral interferences at fat, protein and water wavelengths of the Super-Scan (infra-red meat analyser) due to absorbance by phosphorus (a natural constituent of bone) at the carbohydrate wavelength. Instrument calibration for boneless meat resulted in the need for correction factors to results for bone-in meat of × 0·96, × 1·05 and × 0·97 for % fat, % protein and % water, respectively, to bring them in line with those by standard chemical methods. Comparisons between Super-Scan results for boneless meat to which tricalcium phosphate (the major constituent of bone) has been added showed an interference proportional to the amount of phosphate present and varied in size depending on sample fatness. Calibration with bone-in meat controlled interference adequately for % fat and % water, but still required an empirical correction factor of × 0·97 for protein.

Heifers (n = 70) were slaughtered and hung conventionally in an industrial meat plant. Near infrared (NIR) spectroscopy was studied for its ability to predict selected meat quality attributes, i.e. Warner-Bratzler shear force (WBSF), sensory tenderness, texture, flavour and acceptability. Freshly cut steaks (2.5 cm thick) were taken from the longissimus dorsi (LD) muscle at 1, 2, 7 and 14 days post mortem for NIR analysis. Other samples (also 2.5 cm thick) were taken at 2, 7 and 14 days post mortem, vacuum-packaged in plastic bags and stored at -20 °C for WBSF measurement and sensory analysis. Heifers were slaughtered in two groups; between slaughterings, replacement of the spectrophotometer lamp and lamp assembly was necessitated by a bulb failure. Using principal component regression (PCR), correlation coefficients of 0.82 and 0.73 were obtained for the prediction of WBSF in sample sets 1 and 2, respectively. On merging both sample sets, this value was lowered slightly (r = 0.61). Correlation coefficients obtained for the prediction of tenderness, texture, flavour and acceptability were 0.67, 0.53, 0.51 and 0.46 respectively (set 1); 0.72, 0.71, 0.45 and 0.67 (set 2); 0.53, 0.54, 0.24 and 0.42 (combined sets).

Biopreservation has been proven to be a promising natural preservation technique, but the impact of protective cultures on the sensory properties of cooked meat products (CMP) is not well documented. This work presents a case study on the protective culture Lactobacillus sakei 10A to obtain a clear view on the real consequences of using protective cultures on the sensory quality of CMP. A preliminary screening study on 13 different CMP and more elaborate application trials at 7°C on vacuum packaged pâté, cooked ham, cooked sausage and two cooked poultry products demonstrated that L. sakei 10A inhibits the endogenous LAB-flora, Leuconostoc mesenteroides, Brochothrix thermosphacta and Listeria monocytogenes. Despite these promising antagonistic effects, the application of L. sakei 10A to CMP was in some cases limited by a significant acidification resulting in an acid taste of the product. This was most obvious in pâté and cooked sausage and less obvious in cooked turkey fillet. From the results a hypothesis could be derived that high buffering capacity and low glucose content are key elements to avoid sensory deviations when applying protective cultures on CMP.

Data from 180 bulls from Charolais, Limousine and Retinta breeds were used to evaluate image analysis of cross-sections as method of predicting the physical composition of the 10th-11th-12th rib-cut. The site along the longissimus thoracis muscle (between either the 9th and10th ribs or the 12th and 13th ribs), and the breed had significant influence on most of the variables analyzed. The correlation coefficients between the rib composition obtained by image analysis and by dissection were low to moderate (r=0.18-0.59, P<0.01-P<0.001). The R(2) values of the composition components of the 12th-13th rib cross-section to 10th-11th-12th rib-cut composition were higher than those recorded from the 9th-10th rib cross-section (R(2)=0.535 to 0.759 vs. 0.148 to 0.502). The accuracy of the predictions of lean, longissimus thoracis m. and bone percentages improved significantly with the addition of carcass weight. Results indicate that image analysis can predict rib composition in lean cattle with moderate accuracy and precision.

Transmission infrared analysis, which has been successfully applied to milk analysis, was assessed for the quantitative analysis of fat and protein in meat products. Meats of varying fat and protein content were converted into milk-like emulsions, which were, in turn, analyzed by standard chemical methods and by a Multispec M infrared analyzer. The performance of the instrument for meat analysis using a standard milk calibration was also assessed and compared with the instrument set with a meat calibration. Both approaches provided a good estimate of the fat and protein content for a range of meat products, the meat calibration being more accurate than the milk calibration. The infrared method allowed for rapid and accurate analysis of meat and has future potential in the meat industry for quality control purposes.

The changes in electron micrographs of muscles frozen at -10, -22, -33, -78 and -115°C were analyzed. The ultrastructure of muscle successively changed with decreasing freezing temperature whereas light microscopy indicated anomalous behaviour at -22°C. It appeared that, in muscles frozen at -10°C, there was no freezing of water intracellularly; in those frozen at -22°C, water was frozen intracellularly (but only in the I-band region); whereas, in muscles frozen at -33°C, water was frozen inside the fibres, both in the I- and the A-bands. In muscles frozen at -78 and -115°C, water is frozen intracellularly. These findings can be explained on the basis that, in the I-band region, the major protein is actin, which has a relatively high proportion of non-polar residues and holds water weakly, whereas the predominant protein in the A-band is myosin, which contains many polar residues and has a high water-holding capacity.