MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM: Manipulating meat tenderness by increasing the turnover of intramuscular connective tissue1,2

Abstract

Controlled reduction of the connective tissue contribution to cooked meat toughness is an objective that would have considerable financial impact in terms of added product value. The amount of intramuscular connective tissue in a muscle appears connected to its in vivo function, so reduction of the overall connective tissue content is not thought to be a viable target. However, manipulation of the state of maturity of the collagenous component is a biologically viable target; by increasing connective tissue turnover, less mature structures can be produced that are functional in vivo but more easily broken down on cooking at temperatures above 60°C, thus improving cooked meat tenderness. Recent work using cell culture models of fibroblasts derived from muscle and myoblasts has identified a range of factors that alter the activity of the principal enzymes responsible for connective tissue turnover, the matrix metalloproteinases (MMP). Fibroblasts cultured from 3 different skeletal muscles from the same animal show different cell proliferation and MMP activity, which may relate to the different connective tissue content and architecture in functionally different muscles. Expression of MMP by fibroblasts is increased by vitamins that can counter the negative effects of oxidative stress on new collagen synthesis. Preliminary work using in situ zymography of myotubes in culture also indicates increased MMP activity in the presence of epinephrine and reactive oxidative species. Comparison of the relative changes in MMP expression from muscle cells vs. fibroblasts shows that myoblasts are more responsive to a range of stimuli. Muscle cells are likely to produce more of the total MMP in muscle tissue as a whole, and the expression of latent forms of the enzymes (i.e., pro-MMP) may vary between oxidative and glycolytic muscle fibers within the same muscle. The implication is that the different muscle fiber composition of different muscles eaten as meat may influence the potential for manipulation of their connective tissue turnover.

Study of beef blade muscles’ differentiation depending on conformation and fat class

“…The type of cut is the factor that determines muscle function in vivo as well as marbling, connective tissue proportion, and other factors (9).…”

Use of ractopamine during compensatory gain of finishing pigs on carcass and meat performance and quality

“…Based on these data, the results contradicted the expected hypothesis of a possible synergy between the ad libitum feeding phase, after the restriction period, associated with the use of ractopamine. According to Purslow et al (2012), after a period of food restriction, there is a pronounced increase in the consumption of feed or nutrients when feeding ad libitum. Considering that ractopamine is substrate dependent, a higher dietary substrate value could lead to an increase in performance indices favored by the additive action.…”

“…Then, sub-samples of 2cm width x 1cm thickness x 1cm length were placed on a Stable Micro Systems TA-XT2i texturometer equipped with the Warner-Bratzler blade and the shear force measured perpendicular to the orientation of the muscle fibers (Bouton et al, 1971). The myofibrillar fragmentation index was determined using the method described by Ramos and Gomide (2007 The data were analyzed in a factorial scheme and submitted to analysis of variance. For the variables that did not present an interaction effect, the F test was performed, using the SAEG statistical program (Sistema…, 1997).…”

“…In this context, there are several classic procedures in the literature and even applied in practice that meet these principles including, among others, the food restriction followed by the compensatory gain (Purslow et al, 2012) and the use of ractopamine (Bridi et al, 2006;Agostini et al, 2011).…”

“…The components L* (luminosity), a* (red-green component) and b* (yellow-blue component) were expressed in the CIELAB color system. The saturation index (C*) and the hue angle (h*) were evaluated according to the guidelines of Ramos and Gomide (2007).…”