Contribution of intramuscular connective tissue components in determining the meat texture of Bos indicus cows

Abstract

The Brazilian beef shows inconsistency in tenderness. Alternatives to the industry could ease this problem, but would affect the costs of the final product. Historically, a considerable part of the annual slaughter of cattle in Brazil is composed of females. The majority of females slaughtered are cows for disposal, approximately 6 years and with a large inconsistency in tenderness. The objective of this project is to evaluate the contribution of the myofibrillar components (types of collagen and solubility) of intramuscular connective tissue during the meat maturation process of adult females.In the experiment, 36 cows for disposal with ages varying between 4 to 12 years and belonging to Nellore breed will be slaughtered. The carcasses will be initially evaluated for qualitative and quantitative traits, and then the pairs (right and left) of three muscles that have different levels of collagen and have different levels of tenderness, will be removed from the carcasses. The tenderness of the steaks will be evaluated subjectively, by tasting panels, and objectively, by shear force, after maturation into four distinct periods of time. The independent variables include: myofibrillar fragmentation in raw and cooked samples; caseinolityc activity of ¼-calpain and inhibitory activity of calpastatin by spectrophotometry after liquid chromatography; gene expression of protease inhibitors determined by quantitative PCR; levels of soluble and insoluble collagen, determined by quantification of hydroxyproline after enzymatic and chemical treatment; expression of types I and III collagen, determined by SDS PAGE; activity of matrix metalloproteinases, determined by zimography; perimysium thickness, evaluated by light microscopy and measurements of tension in the perimysium after cooking and and measurements of tension in the perimysium after cooking.The experiment is in a completely randomized design with factorial 2x3x4. The tests with measurements obtained in different times of maturation will be analyzed as repeated measures in time. Correlation studies will be performed to identify variables correlated with tenderness. Statistical analysis will be developed using the statistical program R. (R Development Core Team, 2007). (AU)