Factors regulating lamb longissimus tenderness are affected by age at slaughter

Abstract

The objective of this experiment was to determine age-related changes in collagen concentration, sarcomere length, calpain (μ- and m-) and calpastatin activities, postmortem proteolysis and Warner-Bratzler shear force (WBSF) in ovine longissimus thoracis et lumborum. Rambouillet lambs were slaughtered at 2, 4, 6, 8 and 10 months of age and samples of longissimus were collected at 0, 2 and 10 days postmortem. Collagen concentration and sarcomere lengths were determined from the cores used for WBSF measurements and reflected changes in the background toughness. Longissimus collagen concentration did not change (P>0.05) due to lamb age. Sarcomere lengths also showed age-related changes, increasing (P<0.05) from 1.35 μm at 6 months to 1.48 and 1.55 μm at 8 and 10 months, respectively. The extent of calpain mediated proteolysis determines the improvement in meat tenderness with postmortem storage. The most notable change in the calpain proteolytic system was the decline (P<0.05) in calpastatin activity from 4.18 to 1.91 U/g muscle between 2 and 10 months. The activity of μ-calpain showed a 16% increase (P<0.05) from 4 to 6 months, before it dropped again at 8 and 10 months. There was a gradual decline (P<0.05) in m-calpain activity with age, and by 10 months m-calpain activity had reduced to 80% of 2 months levels. The ratio of μ-calpain to calpastatin activities increased (P<0.05) from 2 to 6 months (from 0.31 to 0.56) with no further changes (P>0.05) at 8 or 10 months. There were no age-related changes (P>0.05) in desmin degradation at day 2, however, examination of day 10 samples showed increased (P<0.05) degradation from 2 to 6 months. Thus, the changes observed in the ratio of μ-calpain to calpastatin activities are reflected in the extent of postmortem proteolysis. Meat tenderness was measured using WBSF at 2 and 10 days postmortem. Because little proteolysis had taken place at 2 days postmortem, the decline in day 2 WBSF from 6 to 8 months could be explained by changes in sarcomere length. However, at 10 days postmortem, where WBSF was shown to decrease from 2 to 8 months, the improvement in tenderness could be explained by the amount of postmortem proteolysis. The data presented in this paper show evidence that sarcomere length is the main determinant of background toughness in ovine longissimus, and that postmortem proteolysis, resulting from μ-calpain activity regulated by calpastatin, is the main determinant of ovine longissimus tenderization during aging. Thus, lamb longissimus tenderness after refrigerated storage is determined by postmortem proteolysis and its interaction with sarcomere length.

The effect of maternal nutrient restriction during late gestation on muscle, bone and meat parameters in five month old lambs

“…Tenderness has been found to be related to the rate and extent of post mortem proteolysis by the calpain system (Veiseth et al, 2005). However, nutritional studies investigating the effect of altered post natal growth rate on the activity of the calpain system have shown contradicting results (Higgins et al, 1988;Thomson et al, 1992;Speck et al, 1993;Therkildsen et al, 2002aTherkildsen et al, , 2004.…”

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

“…Although the content and composition of IMCT in meat does undoubtedly contribute to cooked meat toughness and vary between muscles and with animal age, the lack of an easy means of manipulating the IMCT content and its contribution to cooked meat toughness has meant that the principal focus of research into variations in meat tenderness has been on the proteolysis of myofibrillar proteins postmortem, taking the view that the IMCT component in any one muscle represents a relatively fixed background toughness in animals of similar age (Koohmaraie, 1994). The idea that IMCT provides a background toughness not affected by immediate preslaughter factors or postmortem carcass handling has persisted in recent literature (Ngapo et al, 2002;Veiseth et al, 2004;Moon, 2006;Damez et al, 2008;Christensen et al, 2011;Du et al, 2011).…”

Effects of carcass maturity on meat quality characteristics of beef semitendinosus muscle for chinese native yellow steers

“…0.05) in total collagen content for all maturity groups. Veiseth et al (2004) also noted that lamb longissimus collagen concentration, in either raw or cooked sample, did not change with age.…”