Biochemical factors regulating the toughening and tenderization processes of meat

Biochemistry of postmortem muscle - lessons on mechanisms of meat tenderization.

http://www.icomst.helsinki.fi/previous_congress/ICoMST%2052/ICoMSTpresentations/Monday/Koohmaraie.pdf

Contribution of postmortem muscle biochemistry to the delivery of consistent meat quality with particular focus on the calpain system

Regulation of feed intake rumen microbiology and fermentation nutrient absorption and splanchnic metabolism endogenous regulatory and pregnancy lactation tissue growth host resistance against parasites and pathogens.

Ruminant Physiology: Digestion, Metabolism, Growth and Reproduction

Meat quality describes the attractiveness of meat to consumers. The present paper focuses on two major aspects of meat quality, tenderness and flavour. Both aspects of quality can be influenced by nutrition, principally through its effects on the amount and type of fat in meat. In several countries, high levels of intramuscular fat (marbling fat), i.e. above 30 g/kg muscle weight in longissimus, are deemed necessary for optimum tenderness, although poor relationships between fat content and tenderness have generally been found in European studies, where fat levels are often very low, e.g. below 10 g/kg in UK pigs. Muscle lipid may be a marker for red oxidative (type 1) muscle fibres which are found at higher concentrations in tender muscles and carcasses. Nutritional treatment can be used to manipulate the fatty acid content of muscle to improve nutritional balance, i.e. increase the polyunsaturated (PUFA): saturated fatty acid value and reduce the n-6:n-3 PUFA value. Increasing PUFA levels may also change flavour because of their greater susceptibility to oxidative breakdown and the generation of abnormal volatile compounds during cooking. This situation particularly applies to the n-3 PUFA which are the most unsaturated meat lipids. In pigs, a concentration of 3 mg alpha-linolenic acid (18:3)/100 mg in muscle and fat tissue fatty acids can easily be achieved by including whole linseed in the diet. This level has led to abnormal odours and flavours in some studies, but not in others. In cattle and sheep, feeding whole linseed raised 18:3 concentrations in muscle fatty acids from about 0.7 mg/100 mg to > 1 mg/100 mg. As with pigs, this diet also increased levels of long-chain n-3 PUFA formed from 18:3, including eicosapentaenoic acid (20:5). Although this increase led to greater oxidative breakdown of lipids during storage and the generation of large quantities of lipid-derived volatile compounds during cooking, there were no deleterious effects on odour or flavour. When 18:3 levels are raised in lamb and beef because of grass feeding, the intensity of the flavours increases in comparison with grain-fed animals which consume and deposit relatively more linoleic acid (18:2). In ruminants, very high levels of 18:2 produced by feeding protected oil supplements cause the cooked beef to be described as oily, bland or pork-like.

/pdf/manipulating-meat-quality-and-composition-398ut9gdpg.pdf

Manipulating meat quality and composition.

The present experiment was conducted to determine the effect of the callipyge phenotype on traits affecting muscle growth and meat tenderness. Dorset wethers (N = 40) that were either carriers or non-carriers were fed grain and slaughtered at 169 d of age. Callipyge phenotype did not affect (P > .05) slaughter weight, hot carcass weight, or weights of the heart, spleen, viscera, kidney-pelvic fat, head, and pelt; however, callipyge lambs had a higher dressing percentage and lighter lungs, liver, and kidneys (P .05) weights of infraspinatus or supraspinatus. Longissimus pH and temperature declines were not affected (P > .05) by phenotype. Longissimus myofibril fragmentation index was lower at 1 (27%), 7 (35%), and 21 (37%) d postmortem and Warner-Bratzler shear force was higher at 1, 7, and 21 d postmortem in the callipyge phenotype (P .05). Longissimus and semitendinosus RNA concentration, DNA content, RNA content, protein content, and the RNA:DNA ratio were higher (P < .05), but DNA concentration, protein concentration, and protein:DNA were not affected in the callipyge phenotype. The higher calpastatin activity associated with callipyge suggests that protein degradation may be reduced in the live animal. Additionally, the increased muscle DNA content associated with the callipyge phenotype suggests an increase in satellite cell proliferation, and results in an increased capacity of skeletal muscle to accumulate and maintain myofibrillar protein. These results suggests that both reduced rate of protein degradation and higher capacity for protein synthesis are consequences of the callipyge condition.

/pdf/a-muscle-hypertrophy-condition-in-lamb-callipyge-h1k3znpd5e.pdf

A muscle hypertrophy condition in lamb (callipyge): characterization of effects on muscle growth and meat quality traits.

Restriction fragment length polymor- phisms (RFLP) have been identified at the bovine calpastatin locus The objective of the present study was to determine whether these polymorphisms are related to variations in calpastatin activity or beef tenderness in unrelated animals of mixed breeding A sample of 83 crossbred steers from sires representing eight different breeds was examined to determine this relationship A 22-kb cDNA coding for domains 2 through 4 plus a 3' untranslated region of bovine skeletal muscle calpastatin was used as a probe for calpastatin RFLP Polymorphisms were found using the restriction enzymes BamHI and EcoRI Poly- morphic restriction fragments for BamHI were 90 and 50 kb and for EcoRI were 60 and 40 kb Allelic frequencies for BamHI restriction fragments were 53 for the 90-kb allele and 47 for the 50-kb allele Allelic frequencies for EcoRI restriction fragments were 43 for the 60-kb allele and 57 for the 40-kb allele No polymorphisms were identified using the restriction enzymes BglII, DraI, or PstI No associations between EcoRI and BamHI RFLP and 24-h calpastatin activity or Warner-Bratzler shear force at 14 d postmortem were detected Therefore, the polymorphic EcoRI and BamHI restriction sites within the bovine calpastatin locus do not detect DNA sequence differences responsible for variation in cal- pastatin activity or tenderness of aged beef Therefore, these polymorphisms cannot be used to predict tender- ness of aged beef from unrelated animals of mixed breeding These results do not exclude the possibility that other DNA sequences in or near the bovine calpastatin gene are responsible for variation in calpastatin activity or meat tenderness The lack of a relationship between these calpastatin RFLP and meat tenderness must be distinguished from the well- documented relationship between calpastatin activity and meat tenderness Therefore, further development of calpastatin-based methods for predicting beef tenderness in unrelated animals of mixed breeding should focus on basic factors influencing calpastatin activity at the molecular and cellular level

/pdf/relationship-of-restriction-fragment-length-polymorphisms-52zyfdvos1.pdf

Relationship of restriction fragment length polymorphisms (RFLP) at the bovine calpastatin locus to calpastatin activity and meat tenderness

An indirect antibody ELISA was developed for rapid and sensitive quantification of skeletal muscle calpastatin. Polyclonal antibodies were raised in rabbits against recombinant calpastatin, corresponding to domains 2, 3, and 4 of bovine skeletal muscle calpastatin. Western blot analysis revealed that these antibodies specifically recognize an immunoreactive calpastatin protein of approximately 130 kDa in prerigor skeletal muscle extracts. The intensity of the immunoreactive bands corresponds qualitatively with assayable calpastatin activity. For ELISA development, optimum dilutions of sample, primary anti-calpastatin antibody, and peroxidase-conjugated secondary antibody were determined by titration. A dilution optimum for coating of Immulon 4 (Dynatech) plates was observed when heated muscle extracts were diluted to 2 to 4 micrograms of protein/mL and incubated for 2 h at 37 degrees C. Optimum primary (30 micrograms IgG/mL) and secondary (Sigma A-6154; 1:1000 dilution) antibody incubations were for 1 h at 37 degrees C. Tetramethylbenzidine was used as substrate and A450 of the stopped reaction product was recorded in an automated plate reader. Calpastatin ELISA results were linearly related to calpastatin activity (calpain inhibitory activity) of heated longissimus muscle homogenates from prerigor lamb (r2 = .89; n = 40) and beef aged for 24 or 48 h (r2 = .90; n = 47). Intra-assay CV was < 5% (n = 8) and inter-assay CV was < 6% (n = 5). This assay offers advantages of speed, simplicity, and sensitivity over conventional methodology for calpastatin quantification.

/pdf/development-of-an-enzyme-linked-immunosorbent-assay-elisa-28yk1jqa3l.pdf

Development of an enzyme-linked immunosorbent assay (ELISA) for quantification of skeletal muscle calpastatin

Forty-eight crossbred rabbits were used in three replications of a 2 x 4 factorial arrangement to investigate the short-term responses of tissue accretion, calpains and calpastatin activity, and nucleic acid and protein concentrations to beta-adrenergic agonist (BAA) feeding Rabbits were fed a 17% CP diet with or without 7 ppm of L644,969 and slaughtered after 1, 4, 8, or 16 d of treatment Empty body dressing percentage and biceps femoris weight (as a percentage of empty body weight [EBW]) were significantly higher in the treated rabbits than in the controls after 16 d of treatment Heart and liver weights (as a percentage of EBW) were higher (P < 05) after 1 d and liver weight (as a percentage of EBW) was lower (P < 05) after 16 d in treated vs controls Except for an elevation of skeletal muscle m-calpain after 16 d, BAA-supplementation did not affect the calpain-calpastatin system Muscle RNA concentrations and RNA:DNA ratios were higher (P < 05) in treated rabbits after 1 d and remained higher thereafter Protein:RNA ratios were lower (P < 01) in treated than in control rabbits after 4 d and remained lower throughout the trial Muscle DNA content was lower after 4 d and higher after 16 d; RNA content was higher after 4, 8, and 16 d; and protein content was higher after 16 d in treated vs control rabbits Liver nucleic acid and protein concentrations were not affected by BAA treatment(ABSTRACT TRUNCATED AT 250 WORDS)

/pdf/temporal-response-of-rabbits-to-beta-adrenergic-agonist-4srseiqiuo.pdf

Temporal response of rabbits to beta-adrenergic agonist feeding: tissue weight, calpains and calpastatin activities, and nucleic acid and protein concentrations.

Steven M. Lonergan

Papers

A muscle hypertrophy condition in lamb (callipyge): characterization of effects on muscle growth and meat quality traits.

Relationship of restriction fragment length polymorphisms (RFLP) at the bovine calpastatin locus to calpastatin activity and meat tenderness

Development of an enzyme-linked immunosorbent assay (ELISA) for quantification of skeletal muscle calpastatin

Temporal response of rabbits to beta-adrenergic agonist feeding: tissue weight, calpains and calpastatin activities, and nucleic acid and protein concentrations.