Effect of glycogen concentration and form on the response to electrical stimulation and rate of post-mortem glycolysis in ovine muscle
ABSTRACT The associations between the muscle glycogen concentration and form and the rate of post-mortem glycolysis in ovine muscle were investigated. Twenty-two merino wethers (18-24 months) were allocated to either roughage or concentrate pelleted diets for 34 days prior to slaughter. An exercise depletion/repletion model was applied four days prior to slaughter to generate differences in muscle glycogen levels at slaughter. Muscle biopsies were taken from the m. semimembranosus (SM) and m. semitendinosus (ST) prior to and immediately after exercise for muscle glycogen determination. At slaughter, one side was electrically stimulated and both sides were conventionally chilled for 24h. The pH response to electrical stimulation (ΔpH) and the rate of pH decline adjusted to a constant temperature of 38°C over the initial 6h post-mortem period was determined in three muscles (m. longissimus thoracis et lumborum LTL, SM and ST). In addition, the concentrations of glycogen, proglycogen (PG), macroglycogen (MG) and lactate in the three muscles immediately after slaughter were determined. The glycogen loss due to exercise was influenced by diet (P<0.01; concentrate 63% and roughage 73%) but did not differ between muscles. The rates of repletion significantly varied between muscles (SM>ST) and diet (concentrate>roughage). The available glycogen (glycogen(A)) and MG concentrations at slaughter varied significantly depending on the diet (P<0.01) and muscle (P<0.001). The percentage of MG relative to MG+PG varied between muscles (46%, 50% and 57% for the ST, LTL and SM). The concentration and form of available glycogen at slaughter did not influence the response to electrical stimulation after adjusting for pre-stimulation pH (P<0.01). The ΔpH varied significantly between muscles (0.39±0.03, 0.26±0.02 and 0.20±0.03 for the ST, LTL and SM) after adjusting for pre-stimulation pH. Differences in the temperature adjusted rate of pH decline were observed between the muscles (LTL>SM>ST). Importantly, a positive linear association (P=0.05) was found between muscle glycogen(A) concentration at slaughter and the rate of pH decline (temperature adjusted).
SourceAvailable from: ocean.kisti.re.kr[Show abstract] [Hide abstract]
ABSTRACT: This study was carried out to investigate the effect of cooking condition on the water-soluble flavor precursors relevant to postmortem glycogen metabolisms in various beef muscles from Hanwoo (Korean cattle). The loins, striploins, top rounds, and eye of rounds from 40-mon-old heifers were cooked in either with water bath (wet-cooking) or household electric oven (dry-cooking) until attained to about of internal temperature before the measurements of amounts of macroglycogen, proglycogen, free glucose, and lactate. The macroglycogen and proglycogen contents were not significant differences in all beef muscles between the wet-cooking and dry-cooking treatments. Regardless of cooking condition, the both loin and top round had higher (pHangug chugsan sigpum haghoeji = Korean journal for food science of animal resources 12/2013; 33(6). DOI:10.5851/kosfa.2013.33.6.752 · 0.25 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Canada B4 beef carcasses are penalized because the longissimus thoracis (LT) at the grade site (12-13th ribs) is darker than the color threshold for normal bright cherry-red beef. Previous studies have shown that not all B4 carcasses have pH>6.0; therefore, the relationship between LT pH and meat quality was investigated by collecting thirty half-carcasses comprised of the following: ten Canada AA (AA, control), ten B4 with LT pH>6.0 (CL, classic), and ten B4 with LT pH<6.0 (AT, atypical). LT from CL carcasses had the lowest mean lactate level, lowest glucidic potential and highest mean pH value. LT muscle from CL and AT carcasses was dark and had decreased purge, drip loss and cooking loss. Warner-Bratzler shear force values and sensory panel results showed that AT beef was toughest (P<0.0001), substantiating economic penalty. Causal mechanisms for AT carcasses may be inconsistent with traditional DFD theory because of close to normal final muscle pH.Meat Science 08/2014; 98(4):842-849. DOI:10.1016/j.meatsci.2014.07.029 · 2.23 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Insulin-responsive glucose transporter 4 (GLUT4) is a member of the glucose transporter family and mainly presents in skeletal muscle and adipose tissue. To clarify the molecular structure of porcine GLUT4, RACE was used to clone its cDNA. Several cDNA clones corresponding to different regions of GLUT4 were obtained by amplifying reverse-transcriptase products of total RNA extracted from Landrace porcine skeletal muscles. Nucleotide sequence analysis of the cDNA clones revealed that porcine GLUT4 cDNA was composed of 2,491 base pairs with a coding region of 509 amino acids. The deduced amino acid sequence was over 90% identical to human, rabbit and cattle GLUT4. The tissue distribution of GLUT4 was also examined by Real-time RT-PCR. The mRNA expression abundance of GLUT4 was heart>liver, skeletal muscle and brain>lung, kidney and intestine. The developmental expression of GLUT4 and insulin receptor (IR) was also examined by Real-time RT-PCR using total RNA extracted from longissimus dorsi (LM), semimembranosus (SM), and semitendinosus (SD) muscle of Landrace at the age of 1, 7, 30, 60 and 90 d. It was shown that there was significant difference in the mRNA expression level of GLUT4 in skeletal muscles of Landrace at different ages (pAsian Australasian Journal of Animal Sciences 05/2010; 23(5). DOI:10.5713/ajas.2010.90313 · 0.56 Impact Factor