Effect of selection for growth rate on the ageing of myofibrils, meat texture properties and the muscle proteolytic potential of m. longissimus in rabbits

The effect of selection for growth rate on the degradation of the myofibrillar proteins and on meat texture properties of rabbit longissimus muscle at two ageing times (1 and 7 days) was studied as well as its effect on the proteolytic potential of the muscle. Two groups of contemporary animals (20 rabbits per group), one selected for growth rate (S) for 14 generations and the other unselected control group (C) were compared. The control group was formed from the offspring of the embryos belonging to the 7th generation and was compared with selected animals belonging to 21st generation. Myofibrillar protein degradation was studied by SDS-PAGE electrophoresis (12.5% and 4-15% polyacrylamide gels) followed by densitometric analysis of the pherograms. Texture properties were evaluated by Warner-Bratzler (WB) test and Texture profile analysis (TPA). The activities of proteolytic enzymes calpains and cathepsins and of their inhibitors were determined in the muscle at 24h. Densitometric analysis of the pherograms of samples aged 7 days showed an extra 30kDa band and the disappearance of a band with higher molecular weight than the myosin heavy chain with respect to samples aged 24h in both groups of rabbits. TPA results showed that cohesiveness was significantly lower in meat at 7 days than at 24h (P<0.0001), whereas springiness and chewiness presented a clear tendency to be lower at 7 days than at 24h (P=0.0646 and P=0.0764, respectively). Regarding the genetic type, S animals presented higher hardness and chewiness than C rabbits. Shear firmness (WB test) was significantly (P<0.0001) higher for S group, whereas no significant differences in shear force and area were found. No significant effect (P>0.05) of ageing time was detected using WB test. Selection for growth rate did not affect the activities of proteolytic enzymes or their inhibitors.     

Factors associated with tenderness in young beef

One hundred and twenty-two crossbred steers of varying percentages of Bos Indicus and Bos Taurus breeding were slaughtered to determine the relationship of carcass and meat characteristics to tenderness. Carcasses were graded and longissimus dorsi muscle samples were evaluated for fibre type characteristics, sensory and shear force determination, sarcomere length, intramuscular fat content, collagen content and solubility and fragmentation index. Sarcomere length and collagen content and solubility were not significantly related to shear force values or sensory tenderness ratings. The fragmentation index was highly correlated to sensory tenderness ratings (r = −0·60) and shear force values (r = 0·53) indicating that variation in tenderness is associated with myofibrillar protein degradation. A four variable regression equation that included fragmentation index, lean colour, marbling and per cent red fibres accounted for 56% of the variation in sensory tenderness. Fragmentation index directly accounted for 30% of the variation in sensory tenderness in the four variable equation.     

Effect of selection for growth rate on biochemical, quality and texture characteristics of meat from rabbits

Biochemical characteristics, including myosin heavy chain I (MHC-I) percentage, isocitrate dehydrogenase and aldolase activities, meat quality traits and instrumental texture properties of rabbits selected for different growth rates were studied. The animals of the control (C) group (7th generation; n=60) were raised in parallel with those of selection (S) group (21st generation; n=60). Carcass weights (1230.1 ± 19.8 and 1348.3 ± 20.1 g, for C and S, respectively) and perirenal and scapular fat content differed significantly (P<0.01) between the two groups. Water holding capacity was expressed as the percentage of pressure released water and was significantly different (P<0.05) between groups C and S (33.29% and 35.57%). MHC-I percentage and aldolase activity also differed significantly (P<0.05) between groups, group C showing higher oxidative traits than group S (MHC-I: 12.5% and 9.8%; aldolase: 597.11 and 636.83 UI/g muscle). Texture properties from the Warner-Bratzler test showed higher (P<0.001) shear firmness for loin in the S group (1.69 kg/s cm²) than in the C group (1.34 kg/s cm²). In addition, the texture profile analysis indicated that chewiness, gumminess and hardness were also higher in the S group (P<0.01). In conclusion, the results confirmed a positive effect of the selection on productive traits and a negative effect on instrumental texture properties and on the water holding capacity of the meat.     

Effect of age and cut on tenderness of South African beef

The tenderness characteristics of 15 primal cuts of beef of three different age groups were assessed, and the most reliable cut to predict carcass tenderness was determined. Fifteen wholesale cuts from each age group, representing the full variation in fatness, were aged, cooked and underwent sensory evaluation, shear force resistance and proximate analysis. Collagen content and solubility was determined. Percentage fat was used as a covariant during statistical analyses. Tenderness, residue and collagen solubility of all cuts decreased significantly with animal age. Collagen solubility was the largest discriminant between the three age groups, while animal age had no significant effect on collagen content. Tenderness of primal cuts from the same carcass varied considerably, with collagen content and shear force resistance as the largest discriminants between the cuts. Cuts most representative of total carcass tenderness were M. vastus lateralis, M. semimembranosus, M. gluteobiceps, M. semitendinosus and M. triceps brachii caput longum.     

Effect of cooking temperature and time on the physico-chemical, histological and sensory properties of female carabeef (buffalo) meat

The effect of cooking temperature (80-100°C) and time (30-60min) on collagen solubility of Semimembranosus muscle in carabeef were investigated. The pH, cooking loss, shear force value, collagen content, collagen solubility, sensory evaluation and histological observations of water bath cooked and pressure cooked Semimembranosus meat samples were measured. Increase in pH, cooking loss, collagen solubility and tenderness scores with decrease in shear force value and collagen content was observed with increases in cooking temperature and time. However, no statistical difference was observed for shear force values, collagen solubility values and tenderness scores in pressure cooked meat and meat cooked in a water bath at 100°C for 45min, inferring that cooking of buffalo meat at 100°C for 45min improved collagen solubility and tenderness to the same extent as that due to pressure cooking.     

肌肉胶原蛋白特性对嫩度的影响

本试验对不同月龄苏尼特羊不同部位的肌肉胶原蛋白特性进行了分析。其结果表明,随着月龄的增加,总胶原蛋白、可溶性胶原蛋白、不溶性胶原蛋白的含量都呈增加的趋势,而可溶性胶原蛋白的溶解度却在随月龄的增加呈下降的趋势。相关分析表明,肌肉的剪切值与总胶原蛋白、可溶性胶原蛋白为极显著正相关(P<0.01),胶原蛋白溶解度与剪切值成极显著(P<0.01)负相关。这些结果表明,通过测定肌肉胶原蛋白的含量可以较客观的评价肉的嫩度。     

Changes in carcass composition and meat quality when selecting rabbits for growth rate

Sixty rabbits from the 23rd generation (group S) of a line selected for growth rate were compared to sixty rabbits from the 7th generation of the same line (group C) to study possible relevant changes in carcass composition and meat quality due to the selection and the consequent decrease in degree of maturity at slaughter weight (2000 g). The only relevant changes in carcass composition were an increase in kidneys, liver and dissectible fat percentages and a decrease in meat to bone ratio of the hind leg. In m. Longissimus, group S had lower yellowness of the carcass and higher redness and yellowness of the meat. ICDH activity increased and the aldolase:ICDH ratio decreased. In the hind leg, group S had higher values of PUFA, PUFA/SFA ratio and n − 3 fatty acids.     

A Bayesian approach to the effect of selection for growth rate on sensory meat quality of rabbit

The effect of selection for growth rate on the sensory characteristics of rabbit meat was assessed by comparing a selected and a control population of rabbits. Embryos belonging to generation 7th were frozen, thawed and implanted in does in order to produce the control group. The control group was formed from the offspring of the embryos belonging to the 7th generation. Selected animals belonging to 21st generation (S) were compared with animals of the control group (C), both were contemporary. Forty animals per group were slaughtered at 9-weeks-old. The sensory analysis was carried out on samples of the Longissimus dorsi muscle. The parameters evaluated were: intensity of rabbit flavour (IRF), aniseed odour (AO), aniseed flavour (AF), liver flavour (LF), tenderness (T), juiciness (J), fibrousness (F). A Bayesian analysis was performed. The ratio of the selection and control effects was analysed. There was a difference between the selected and control groups for IRF, AO, AF and LF. Conversely, no differences were found in T, J and F between groups. Selected group had 3% and 23% higher values of IRF and LF, respectively, than the control group. A relevant effect of selection on AO and AF appeared (probability of relevance P(r)=1), with lower values for selected animals. There was a difference between male and female groups for IRF, but this was not relevant. No differences between sexes were found for the rest of the characteristics evaluated. Selection for growth rate did not affect the main sensory characteristics of meat, like T and J but, it had a negative effect on some flavour characteristics.     

Comparison of texture and biochemical characteristics of three rabbit lines selected for litter size or growth rate

Meat texture and some biochemical characteristics that could influence meat tenderness were studied in rabbit loins. Rabbits from three synthetic lines were compared, lines V and A selected for litter size at weaning and line R selected for growth rate between weaning and slaughter time. The activities of cathepsins, collagen content and textural properties measured by Warner-Bratzler (WB) shear device and by the texture profile analyses (TPA) test were measured. Line R was more tender than line V and line A had an intermediate tenderness, Rabbit meat from line R had higher activity of cathepsins B and B + L, lower total collagen content and lower cohesiveness, springiness and chewiness, shear force and total work (area under the curve obtained with WB device) than line V. Line A had an intermediate texture between lines R and V. Our results show evidence of genetic variation between lines in rabbit meat tenderness.     

冻融次数对牦牛肉胶原蛋白特性及品质的影响

为探究冻融次数对牦牛肉胶原蛋白特性和品质的影响。以牦牛肉为研究对象,分析不同冻融次数下牦牛肉剪切力、pH、解冻损失、蒸煮损失、色差、质构、胶原蛋白含量及溶解性、酶活性及微观结构的变化规律。结果表明,随着冻融次数的增加,牦牛肉剪切力下降了59.72%,牦牛肉胶原蛋白溶解性、β-半乳糖苷酶和β-半乳糖醛酶活力、解冻损失、蒸煮损失和b^*值显著上升(P<0.05),胶原蛋白含量、剪切力、pH、L^*值、a^*值以及质构显著下降(P<0.05)。相关性分析表明:剪切力与L^*值、a^*值、pH、胶原蛋白含量和溶解性、质构指标呈显著正相关(P<0.01),与解冻损失、蒸煮损失、b^*值、β-半乳糖苷酶活性和β-葡糖醛酸酶活性呈极显著负相关(P<0.001);pH与胶原蛋白特性呈极显著正相关(P<0.001);胶原蛋白特性与质构指标呈极显著正相关(P<0.001)。牦牛肉组织结构随冻融次数增加表现为破坏严重,肌纤维边界模糊。综上,冻融次数增加,...     

Pyridinoline in ovine intramuscular collagen

Pyridinoline, a mature crosslink of collagen, was measured in intramuscular connective tissue isolated from ovine semimembranosus, a muscle noted for its highly insoluble collagen. Concentration ranged between 0·25 and 0·59 mol/mol of collagen, on the high side of concentrations reported in the literature for this and other muscles in various species. Pyridinoline concentration was inversely related to collagen solubility in muscle homogenates (P < 0·0). In a comparison between semimembranosus, biceps femoris and gluteus medius, pyridinoline concentration was again inversely related to collage solubility. For all these muscles, pyridinoline remained insoluble in a heat-dependent solubility test, but it is argued that pyridinoline does not explain all the solubility properties of ovine intramuscular collagen. Pyridinoline concentration was not significantly correlated with sensory or shear properties of cooked semimembranosus, confirming the importance of other heat-stable crosslinks.     

Tenderness of ovine semimembranosus: Is collagen concentration or solubility the critical factor?

The concentration and heat-dependent solubility of collagen were measured in the semimembranosus (36 animals) and, for comparison, the gluteus (108) muscles of sheep aged 4 months to 5 years. For both muscles, solubility declined with age but concentration remained unchanged. Compared to gluteus and other major ovine muscles, the semimembranosus had markedly insoluble collagen at a relatively low concentration. To assess the relative importance of collagen concentration and solubility on tenderness/texture for a muscle with this profile, the semimembranosus muscles contralateral to those used for collagen analysis were cooked to an endpoint of 75°C and assessed by sensory panel and Warner-Bratzler shear tests. The panel data showed that collagen concentration was the more important determinant of eating quality, whereas shear data were more clearly related to solubility. The implications of the sensory results are discussed for muscles that contain a different collagen profile.     

Factors Affecting Collagen Solubility in Bovine Muscles

SUMMARY— Solubility of intramuscular collagen was studied as affected by chronological maturity in 15 bovine longissimus dorsi and 15 semimembranosus muscles and as affected by post-mortem contraction state in the semitendinosus of 7 animals. Collagen solubility decreased significantly with each advancing maturity group in both longissimus dorsi and semimembranosus muscles. Collagen solubility was also higher (P < 0.05) in the longissimus dorsi than in the semimembranosus, except in the E maturity group. It was also related to panel tenderness in both muscles (r = 0.77 and 0.81 (P < 0.01) for longissimus dorsi and semimembranosus muscles, respectively. However, within-maturity group correlations of solubility of collagen and tenderness were low and nonsignificent.
Collagen content did not differ significantly in longissimus dorsi muscles of animals of A, B, and E maturity groups; however, the semimembranosus had more collagen (P < 0.05) in E than in A and B maturity groups. Collagen content was not related (P > 0.05) to panel tenderness in either muscle (r =−0.42 and −0.48 for longissimus dorsi and semimembranosus, respectively). Neither collagen solubility nor collagen content was significantly affected by post-mortem contraction state. Furthermore, collagen solubility did not increase significantly with post-mortem aging up to ten days.     

Using shear force,sarcomere length,particle size,collagen content,and protein solubility metrics to predict consumer acceptance of aged beef tenderness

In this study, the relationship between sensory evaluation and several objective metrics of beef tenderness was tested. Objective metrics included shear force, sarcomere length, collagen content, myofibrillar, and sarcoplasmic protein solubility and particle size analysis. These results were compared to consumer panel scores of tenderness for the same aged beef striploin (longissimus lumborum muscle) samples. There was found to be a significant relationship between sarcomere length, shear force, and particle size with tenderness scores. Collagen content and protein solubilities were not associated to tenderness scores (p > 0.05). Sarcomere length contributions for explaining tenderness variation were overlapped by the contributions of shear force (collinearity). Independent models demonstrated that the lower 95% confidence interval of the fitted regression line exceeded 50% acceptance of tenderness when shear force values <42.6 N and when particle size values <198 μm. We can recommend these as thresholds for consumer acceptance of beef tenderness, although considerations of sample type, analytical methodology, and consumer demographics should be made prior to their adoption. This provision was based on the variation in tenderness scores evident between individual panelists and experimental striploins.     

Effects of Carcass Maturity on Collagen Solubility and Palatability of Beef from Grain-Finished Steers

Samples from steers fed a high-energy diet for 185 days prior to slaughter were used to compare collagen solubility and palatability of beef from youthful and mature carcasses. Carcasses representing the two maturity classes were selected specifically to have similar levels of intramuscular and subcutaneous fat, but distinctly different maturity indicators. Under the conditions of this study, maturity class had no effect on sensory properties or shear force values of cooked rib steaks. Total collagen content of samples from the longissimus muscle was higher for mature carcasses, but maturity class means for percentage of soluble collagen were not different. The relationships of these findings to preslaughter feeding regimen and collagen metabolism are discussed.     

Changes in carcass composition and meat quality when selecting rabbits for growth rate

Sixty rabbits from the 23rd generation (group S) of a line selected for growth rate were compared to sixty rabbits from the 7th generation of the same line (group C) to study possible relevant changes in carcass composition and meat quality due to the selection and the consequent decrease in degree of maturity at slaughter weight (2000 g). The only relevant changes in carcass composition were an increase in kidneys, liver and dissectible fat percentages and a decrease in meat to bone ratio of the hind leg. In m. Longissimus, group S had lower yellowness of the carcass and higher redness and yellowness of the meat. ICDH activity increased and the aldolase:ICDH ratio decreased. In the hind leg, group S had higher values of PUFA, PUFA/SFA ratio and n − 3 fatty acids.     

Effect of feed energy intake on collagen characteristics and muscle quality of mature cows

Samples from mature cows fed a high-energy and maintenance-energy diet for 84 days prior to slaughter were used to compare collagen solubility and palatability traits. Cows fed a high-energy diet prior to slaughter had increased percentage heat-labile collagen, less sensory panel detectable connective tissue and lower shear force values than cows fed a maintenance-energy diet. Mature cows fed a high-energy diet were fatter and had more marbling than cows fed a maintenance-energy diet. The increased collagen solubility from feeding a high-energy diet to mature cows resulted in palatability and shear force ratings similar to those expected from young animals.     

鸭油甘油二酯食用理化性质分析及油炸牛肉烹调特性评价

通过测定鸭油甘油二酯、鸭油、豆油、牛油的理化性质及对油炸牛肉烹调特性的评价,旨在确定鸭油甘油二酯的食用价值.试验结果表明:鸭油甘油二酯的酸价为2.27±0.07,符合国标规定;丙二醛(MDA)值为0.023±0.01,极显著小于其他3种油脂(P≤0.01);碘值为71.836±3.74,显著高于牛油47.352±3.3...     

Organic Acids as Tenderizers of Collagen in Restructured Beef

Acetic, citric and lactic acid were incorporated into restructured beef steaks to determine their effect on collagen. These steaks were analyzed for collagen solubility, total collagen content, shear force behavior, sarcoplasmic and myofibrillar protein extractability, thermal stability and color. These results were compared to those obtained from control samples containing high collagen and low collagen. Results indicate that these acids increased collagen solubility, total collagen content and shear force values when compared with the control samples. No differences (P > 0.05) were found in sarcoplasmic protein extractability although myofibrillar protein extractability declined. Acid treatment decreased the thermal stability of collagen. The Hunter Color values of the uncooked and cooked acid-treated steaks differed (P 0.05) from the controls.     

Effect of diet,slaughter weight and sex on instrumental and sensory meat characteristics in rabbits

The effect of the fattening diet, slaughter weight and sex on meat quality was studied in a total of 156 hybrid rabbits. After weaning, rabbits were divided into three groups of 52 animals each (50% male and 50% female), that were allocated for three weeks to one of three commercial diets containing low (14.28%, A), medium (18.04%, B) and high (20.48%, C) fibre content with decreasing energy levels. Animals were slaughtered at 2.0 and 2.3 kg after the consumption of a common pre-slaughter non-medicated concentrate and pH, colour, water-holding capacity (WHC), Warner–Bratzler shear test and sensory analysis were all measured. Meat from animals fed with low fibre and high energy was the least luminous. Rabbits slaughtered at 2.0 kg showed more yellowness than at 2.3 kg at 0 min. In both traits, these differences did not prevail after 15 min of blooming. Globally, meat from males was more coloured than that of the females, both at 0 and 15 min of blooming. No significant differences were found for pH, WHC or shear test for the individual effects. In the sensory analysis, rabbit and grass odours were more intense at 2.0 kg than at 2.3 kg of slaughter weight.