The influence of temperature on shortening and rigor onset in beef muscle

At sufficient ATP concentration and temperatures below about 15°C, pre-rigor beef muscles (neck muscles) contract; this phenomenon is known as cold shortening. There is also a contracture at higher temperatures occurring just before rigor onset which is called rigor shortening. While rigor shortening starts in neck muscles at pH around 6·3–6·0 and at about 2 μMol ATP/g muscle, cold shortening can begin at pH around 7·0 and the full ATP concentration (4 μMol ATP/g) in the muscle. Shortening can take place as long as there is no irreversible formation of the actomyosin complex in the muscle, i.e. before rigor onset occurs, which can be measured by intermittent loading of the muscle. The degree of extensibility which follows starts to decrease at the moment of rigor onset. This irreversible loss of extensibility at temperatures between the freezing point (?1°C) and physiological temperatures (38°C) starts at various pH values and ATP concentrations in the muscle. At 38°C the rigor onset occurs at pH 6·25 and about 2 μMol ATP/g muscle, dropping at 15°C to pH 5·75 and 1 μMol ATP/g muscle. At 0°C, as at all temperatures below 10°C, the loss of extensibility at medium loads (about 250 g/cm²) begins shortly after cold shortening. This loss of extensibility is reversible by increasing the load or raising the temperature. The irreversible loss, or rigor onset, however, occurs at 0°C with pH of 6·1–6·2 and 1·8–2·0 μMol ATP/g muscle. Thus, the onset of rigor is influenced by more than one factor. Temperature, pH and ATP concentration each play a rôle.Maximum loss of extensibility or completion of rigor is reached between 10°C and 38°C at pH 5·5–5·6 and less than 0·5 μMol ATP/g muscle. At 0°C the completion of rigor takes place at pH 6·0, but still at 0·5 μMol ATP/g muscle. The latter fact shows that the completion of rigor is solely dependent on the ATP concentration in the muscle; nevertheless, the pH of rigor completion is higher in the extreme cold shortening range. This is apparently due to a different pH/ATP relationship in muscles at low temperatures.The results are discussed in terms of changes in the concentration of Ca²⁺ ions and ATP.The results are of particular interest for the handling of hot-boned meat; that is, for both the cooling of pre-rigor muscle and the use of hot-boned meat for processing.     

Tenderness of pork m. longissimus thoracis et lumborum after accelerated boning. Part I. Effect of temperature conditioning

This research investigated the effect on tenderness and meat quality of temperature conditioning at 0, 7, 14 or 21?°C of pork longissimus muscle after accelerated boning (removal from the carcass within 30 min post slaughter). The conditioning temperature had no effect (P>0.05) on tenderness at the end of the conditioning period (i.e. at the onset of rigor) but had a significant effect (P<0.05) after the muscles were aged for four days at 2?°C. After aging, the muscles conditioned at 14?°C were more tender than muscles conditioned at the other three temperatures; the muscles conditioned at 0?°C were tougher than the muscles conditioned at the higher three temperatures. Conditioning at 14?°C produced muscles that had lighter surface colour and lower drip loss due to prevention of cold toughening which occurred at lower temperatures or protein denaturation at the higher temperatures.     

Effect of calcium infusion on tenderness and ageing rate of pork m. longissimus thoracis et lumborum after accelerated boning

The effect of calcium chloride infusion at either 0.5 or 6 h post slaughter on tenderness, ageing rate and meat quality of pork longissimus muscle that had been boned at rigor or had undergone accelerated processing and conditioning at either 0?°C or 14?°C was investigated. The time of calcium infusion had no effect on the initial WBSF values or the aging rate. However, calcium infusion overall resulted in lower WBSF initially (1-day post-mortem) and also after 6 days ageing at 2?°C regardless of the processing procedures used. Calcium infusion did not, however, increase the ageing rate compared to comparable treatments that had not been calcium infused. Based on this observation and the myofibrillar fragmentation index results, it was concluded that the increased tenderness due to calcium infusion was not due to increased proteolysis as has been previously postulated, but was due to either a direct effect of calcium on tenderness, or an indirect effect of calcium via increased post-mortem glycolysis and pH decline rate resulting in reduced cold shortening. Calcium infusion had detrimental effects on drip loss and meat colour.     

Tenderness of pork m. longissimus thoracis et lumborum after accelerated boning. Part II. Effect of post-slaughter ageing

This research investigated the effect of ageing time (0-10 days) at 2?°C on tenderness of pork longissimus muscle after either rigor boning (RB) or accelerated boning (removal from carcass within 30 min post slaughter) and temperature conditioning at either 0 or 14?°C. Ageing occurred most rapidly in muscles conditioned at 14?°C- maximum tenderization occurred by 4 days post-mortem. RB muscles and muscles conditioned at 0?°C aged more slowly and took 8 and 10 days, respectively, to reach a comparable level of tenderness. Temperature conditioning at 14?°C, produced muscles which had lower drip loss and lighter surface colour.     

Changes in colour of beef m. longissimus dorsi muscle during ageing

The effects of vacuum packaging, chilling rate (slow or fast), and fat cover thickness (?4 mm or 7-8 mm) on the colour parameters of beef m. longissimus dorsi muscle were assessed during ageing. The m. longissimus dorsi muscle was aged on the carcass or in vacuum packaging. Muscle samples for analysis were taken on days 0 (24 hr post mortem), 2, 4, 8, 12 and 16 to ascertain the parameters. Ageing time influenced all colour parameters, while chilling rate affected lightness ('L'), yellowness ('b'), and hue angle difference (HD), and fat cover thickness influenced 'L' and 'b' only.     

Effect of low and high pulsed electric field on the quality and nutritional minerals in cold boned beef M. longissimus et lumborum

The present research investigated the effects of low PEF (LPEF, 2.5 kV, 200 Hz and 20 μs) and high PEF (HPEF, 10 kV, 200 Hz and 20 μs) on the quality of cold-boned beef loins at 1 and 14 days of post-treatment. HPEF increased (P < 0.001) the temperature of the beef M. longissimus et lumborum (LL) samples. HPEF samples had higher (P = 0.007) shear force than LPEF samples and control samples were not different from either. HPEF beef LL samples had higher L* values and lower a* values (P < 0.001) compared to LPEF and control samples. Higher lipid oxidation (P = 0.013) was found in HPEF samples compared to LPEF samples. Lower (P < 0.01) P, K and Fe concentrations were found in HPEF samples compared to LPEF samples. The results suggest that high intensity PEF treatment can negatively affect the quality of beef.     

Effects of muscle shortening and proteolysis on Warner-Bratzler shear force in beef longissimus and semitendinosus

The effect of the addition of the fungal protease EPg222 on the sensory characteristics of dry fermented sausage "salchichón" ripened with commercial starter cultures was investigated. Sausages were prepared with purified EPg222 and Staphylococcus carnosus, Staphylococcus xylosus, and Lactobacillus sakei as starter cultures, ripened for 145 days and compared with a control batch only inoculated with the starter cultures. Dry fermented sausages ripened with EPg222 and starter cultures showed higher amount of NPN and volatile compounds derived from amino acid catabolism, than control ripened only with starter cultures. Several branched aldehydes, acids and alcohols such as 2- and 3-methylbutanoic acid and 2-methylpropanol were detected only in enzyme treated samples. Sensory analysis reflected higher values for aroma intensity of sausages treated with EPg222 and lower values of hardness than control. The effect of EPg222 may be of great interest to improve sensory characteristics of dry fermented sausages ripened with starter cultures.     

Variation of the sensory quality within the m. longissimus thoracis et lumborum of PSE and normal pork

This study evaluated the variation in instrumental and sensory meat quality within the m. longissimus thoracis et lumborum of carcasses with normal and PSE meat. Out of 80 slaughtered pigs, respectively, 9 and 7 carcasses were selected with a pH30 value > or=5.80 (normal pork) and a pH30 value <5.80 (PSE pork). Instrumental and sensory meat quality measurements were performed at three locations on these carcasses: longissimus thoracis (LT), longissimus thoracis et lumborum: (LTL-mid-loin) and longissimus lumborum (LL). Meat of the thoracis site (LT) was paler, but more favourable for pH45, cooking loss, juiciness, tenderness and preference scores than meat of the mid-loin part. The lumborum site (LL) was more or less in between the other two locations for meat quality, but closer to the LTL than the LT site. The meat quality variation within the m. longissimus thoracis et lumborum followed a similar pattern for normal and PSE carcasses. It can be concluded that the mid-loin part is best suited as a reference place for meat quality assessment, if one wants to eliminate carcasses with unacceptable meat.     

Predicting temperature profiles to determine degree of doneness for beef biceps femoris and longissimus lumborum steaks

The degree of steak doneness is an important factor in providing consumers with a satisfying eating experience. Endpoint temperature and cooking rate are the determinants of degree of doneness. Our objectives were to predict internal temperature profiles and cooking times for longissimus lumborum and biceps femoris steaks. Each biceps femoris and longissimus lumborum steak was cooked individually in a gas-fired, forced-air-convection oven at 163 °C until the center temperature of each steak reached 70 °C. Temperature profiles were recorded by a Doric temperature recorder and the recorded time and temperature data were imported into a spreadsheet. A prediction method was then implemented to predict cooking times and temperature profiles. No significant differences (p<0.05) were found in cooking times between experimental and predicted values for either longissimus lumborum or biceps femoris steaks. Good agreement was found between experimental and predicted temperature profiles for the longissimus lumborum muscle. However, predicted temperature profiles were consistently higher (except for the beginning of the cooking cycle) than the experimental values up to 65 °C in the cooking cycle for biceps femoris steaks. A highly positive linear relationship was found between experimental and modeled temperature profiles for longissimus lumborum (R(2)=0.99), whereas a high quadratic (R(2)=0.99) relationship was found for biceps femoris steaks. Our method for predicting temperature profiles of steaks for a specified cooking time to attain a given degree of doneness should increase consumer satisfaction by reducing variation in meat sensory traits related to an expected degree of doneness.     

The use of visible and near infrared reflectance spectroscopy to predict beef M. longissimus thoracis et lumborum quality attributes

Visible and near infrared reflectance spectroscopy was used to predict pH at 24 h (pH24) post-mortem, sarcomere length (SL), cooking loss (CL), Warner–Bratzler Shear Force (WBSF) and colour parameters (L^∗, a^∗, b^∗) in beef cattle samples. Samples from M. longissimus thoracis et lumborum from 30 bulls were aged at 4 °C for 1, 3, 7 and 14 days and analysed for pH, SL, CL, WBSF and colour. NIRS calibrations for pH24, luminosity at 0 (L^∗t0) and 60 min (L^∗t60) showed good predictability (R² = 0.97, 0.85 and 0.82; SECV = 0.10, 1.16, 1.36, respectively), whereas those related to the rest of the parameters were poorer.     

Iron content in musculus longissimus lumborum et thoracis (m.l.l.t.) of fattening pigs

Pork is among the most essential dietary sources of iron in Germany, considering its beneficial absorption rate. During 1997 and 1998 meat samples from 52 pigs per year were collected at the Thuringian performance testing station in order to examine the total iron content of pork. Musculus longissismus lumborum et thoracis (13./14. thoracic vertebra) from the right side of the carcasses were prepared for analyses. The total iron content was measured by atomic emission spectroscopy with inductively coupled plasma. The iron content of the meat was 4.18 +/- 0.97 mg/kg fresh material. This result was significantly lower than corresponding data from literature. An influence of the genetic composition of the pigs examined on the total iron content could be observed. The daily gain (R = -0.26) and intramuscular fat content (R = -0.28) were inversely correlated to the iron content. However, the lean meat proportion (R = 0.26) as well as haem pigment content (R = 0.27) were directly correlated to the total iron content of the meat.     

Ultrasonic scanning measurements of the longissimus thoracis et lumborum muscle to predict carcass muscle content in sheep

Nineteen Omani sheep (average 26 kg body weight) were scanned over the 6th rib, 12th rib and the second-last lumbar vertebra, to determine the maximum depth (B), circumference, area of the cross-section and volume of the longissimus thoracis et lumborum (LD) muscle. The volume of the muscle was estimated by multiplying the average area of its cross-section obtained at the three sites by its length. After slaughter, the LD muscle was dissected out, frozen, and its maximum depth, circumference, length, weight and volume were determined. Correlation and regression analyses were carried out to evaluate relationships between scanning and real measurements and between scanning measurements and carcass total muscle content. Generally there were positive correlations (r = 0.43-0.66) between the LD scanning measurements made at the 12th rib and the corresponding measurements made on the dissected muscle. The volume of the LD muscle estimated from scanning was positively correlated (r = 0.59) with its real volume which was correlated with its weight (r = 0.51) and consequently with the total carcass muscle content (r = 0.69). Ultrasonic scanning can be used to predict the circumference and volume of the LD muscle. These may be used for prediction of total carcass muscle content in sheep in addition to traditional measurements of the muscle (the maximum depth B) and area.     

Tenderness of pre- and post rigor lamb longissimus muscle

Lamb longissimus muscle (n=6) sections were cooked at different times post mortem (prerigor, at rigor, 1dayp.m., and 7 days p.m.) using two cooking methods. Using a boiling waterbath, samples were either cooked to a core temperature of 70 °C or boiled for 3h. The latter method was meant to reflect the traditional cooking method employed in countries where preparation of prerigor meat is practiced. The time postmortem at which the meat was prepared had a large effect on the tenderness (shear force) of the meat (P<0.01). Cooking prerigor and at rigor meat to 70 °C resulted in higher shear force values than their post rigor counterparts at 1 and 7 days p.m. (9.4 and 9.6 vs. 7.2 and 3.7 kg, respectively). The differences in tenderness between the treatment groups could be largely explained by a difference in contraction status of the meat after cooking and the effect of ageing on tenderness. Cooking pre and at rigor meat resulted in severe muscle contraction as evidenced by the differences in sarcomere length of the cooked samples. Mean sarcomere lengths in the pre and at rigor samples ranged from 1.05 to 1.20 μm. The mean sarcomere length in the post rigor samples was 1.44 μm. Cooking for 3 h at 100 °C did improve the tenderness of pre and at rigor prepared meat as compared to cooking to 70 °C, but not to the extent that ageing did. It is concluded that additional intervention methods are needed to improve the tenderness of prerigor cooked meat.     

Use of linear measurements of m. longissimus to predict the muscle content of beef carcasses

Five linear measurements associated with the eye muscle (m. longissimus), together with hot carcass weight, 10th rib fat thickness, eye muscle area and an estimate of eye muscle volume (eye muscle area × a carcass length measurement) were made on 53 chilled beef carcasses (hot weight 143-384 kg). The right side of each carcass was anatomically dissected into muscle, bone, fat and connective tissue. Correlation and regression analyses were used to identify the most accurate predictors of weight and percentage of side muscle. In simple regression, hot carcass weight and the estimate of eye muscle volume were the most accurate predictors of side muscle weight; 10th rib fat thickness and MN, a depth measurement of muscle and fat over the loin, were the most accurate predictors of percentage side muscle. In multiple regression, the addition of either eye muscle volume or eye muscle area to hot carcass weight and 10th rib fat thickness gave the most accurate predictions of side muscle weight and percentage side muscle, but in the case of each dependent variable, the improvement in accuracy was slight compared with that of the two most accurate regressors, hot carcass weight and 10th rib fat thickness. Although eye muscle volume was a more accurate predictor of side muscle weight than eye muscle area in simple regression, their contributions in multiple regression with hot carcass weight and 10th rib fat thickness were similar. None of the five linear measurements associated with m. longissimus contributed significantly to improving the prediction of weight or percentage of side muscle.     

Effects of cooking method, reheating, holding time, and holding temperature on beef longissimus lumborum and biceps femoris tenderness

Effects of cooking method, holding temperature, holding time, and reheating on Warner-Bratzler peak shear force (WBPSF); Warner-Bratzler myofibrillar force (WBM-F), Warner-Bratzler connective tissue force (WBC-F) and cooking loss were investigated. Two muscles (longissimus lumborum and biceps femoris) from USDA Choice beef carcasses were used. Water-bath cooking resulted in higher WBPSF, WBM-F, and WBC-F than belt-grill cooking for longissimus lumborum. The biceps femoris muscle tenderness improved more with holding time after cooking on a belt than the longissimus lumborum due to its higher collagen content. Cooking biceps femoris steaks to 54?°C by a belt grill and holding them at 57?°C in a water bath for 15 min and subsequent reheating to 70?°C (best treatment combination) produced a 25% reduction in WBPSF, a 37% reduction in WBC-F, and a 12% reduction in WBM-F as compared to the control (cooking steaks directly to 70?°C without holding). Water-bath cooking resulted in lower WBPSF than belt-grill cooking for biceps femoris without any holding time, but further tenderization did not occur with holding. Water-bath cooking resulted in higher cooking losses than belt-grill cooking for both muscles.     

Yield point in raw beef muscle. The effects of ageing, rigor temperature and stretch

The yield point of raw sternomandibularis muscle of the ox decreased markedly with ageing. This parameter is the most sensitive and selective indicator of ageing since, unlike shear measurements on cooked meat, it is not complicated by heat denaturation or the contribution of the collagen net. Rigor at 2°C with consequent cold shortening has little effect on yield point, but rigor at 37°C diminishes yield values relative to the 15°C controls. Muscles stretched by 40-60% during rigor show higher yield points. Yield was also studied in other muscles. Unaged strips of bull sternomandibularis, or steer psoas and rectus abdominis tended to break rather than yield, but after ageing usually yielded at the same low loads as aged ox sternomandibularis. The histological changes due to yielding varied widely, but stretched, rather than broken, I-bands were the dominant feature. Our interpretation of the electron micrographs is that in rigor muscle, actin filaments fracture while gap filaments stretch, but in aged muscle both sets of filaments fail simultaneously at low loads.     

Effect of rigor temperature and frozen storage on functional properties of hot-boned manufacturing beef

Within 45 min post-mortem, 10mm thick strips of semitendinosus muscle from both unstimulated and high voltage stimulated heifer sides were held at 0, 5, 10, 25 and 35 °C for 24 hr, during which they entered rigor. Half the samples were frozen and stored at -20 °C for one month. The pH, sarcomere length, drip, total (TPS), myofibrillar (MPS) and sarcoplasmic (SPS) protein solubilities, and Hunter L (?), a (?) and b (?) values were determined at 24 hr and on thawed samples. Electrical stimulation did not significantly affect any of the parameters measured. The ultimate pH of samples entering rigor at 10 and 25 °C was lower (p < 0.001) than that of samples held at the other temperatures. Rather surprisingly, there was no significant difference in sarcomere length due to rigor temperature. Samples entering rigor at 35 °C had lower TPS, MPS and SPS values than samples held at 0 to 25 °C (p < 0.001). The MPS increased with rigor temperature up to 25 °C (p < 0.001). Drip and total moisture losses, and Hunter L (?), a (?) and b (?) values also increased with rigor temperature (p < 0.001) whereas SPS decreased and NMR meat water spin-lattice relaxation time (T1) shortened with increasing rigor temperature (p < 0.001). Hue angle and cook loss decreased with rigor temperature in 24 hr samples but increased with rigor temperature in frozen samples. After frozen storage, SPS, T1, cook loss and Hunter L (?), a (?), b (?) values decreased, but TPS, MPS, drip losses and hue angle increased. There were significant (p < 0.05) correlations between SPS, hue angle, drip losses and T1.     

Variation in Flavor and Textural Descriptions of Cooked Steaks from Bovine m. longissimus thoracis et lumborum from Different Production and Aging Regimes

ABSTRACT: Free choice profiling (FCP) and generalized Procrustes analysis (GPA) were used to assess flavor differences in cooked bovine m. longissimus thoracis et lumborum (LTL) steaks sourced wholesale or from steers fed the same diet. Wholesale steaks were from LTL muscles that were either unaged or aged for 93 d with high or low visible marbling from old and young grass- and grain-finished cattle. The GPA of this sensory data showed that the 1st dimension contrasted grass- and grain-finished beef and accounted for 44.1% of the total variance, whereas the 2nd dimension contrasted unaged and aged beef and accounted for 22.9% of the variance. GPA was also used to assess flavor variation in cooked LTL steaks aged 4 or 14 d postmortem from 10 steers finished on the same diet, and the 1st 2 dimensions accounted for 39% of the total variance. Univariate analysis of beef aroma, flavor intensity, tenderness, and juiciness showed only tenderness increased with aging ( P = 0.041) and Duncan's multiple comparison test on all FCP data indicated that aging beef up to 14 d shifted beef sensory characteristics toward increased tenderness, juiciness, and fatty flavor. The results of these studies showed that distinct flavors exist in beef from cattle finished in different production systems and that there is less variation in the flavor of beef from steers produced on the same farm than in beef available for general retail.     

Measuring the effects of phenotype and mechanical restraint on proteolytic degradation and rigor shortening in callipyge lamb longissimus dorsi muscle during extended aging

The purpose of this study was to determine if tenderness of callipyge (CLPG) longissimus dorsi muscle (LM) could be improved by: (1) extending the aging period to 48 days postmortem or (2) preventing rigor shortening by clamping. In CLPG and normal (NML) chops respectively, initial Warner-Bratzler shear values (WBS) were lower (P<0.05) in clamped (CL) (5.5 and 3.6 kg) compared to unclamped (UCL) (7.4 and 4.9 kg) LM. In CLPG, an acceptable WBS (3.6 kg) was reached at 48 days PM, whereas, NML lambs reached an acceptable level (3.8 kg) by 3 days PM. Sarcomere lengths (SL) of CL (1.68 μm) were longer (P <0.05) than for UCL (1.44 μm) and were negatively correlated with WBS (r=-0.55; P<0.1). The appearance of Troponin-T (TNT) degradation product coincided with tender WBS values; 3 days postmortem in NML UCL and 48 days postmortem in CLPG. In conclusion, clamping reduced WBS possibly by reducing rigor shortening. Extended aging resulted in CLPG LM with acceptable WBS values, concurrent with the appearance of TNT degradation products.     

The influence of season on quality characteristics of hot-boned beef m. longissimus thoracis

Samples of m. longissimus thoracis (LT) muscle were randomly collected from 70 Omani beef cattle 1 h after slaughter between August 2001 and July 2002 in the Muscat Municipality central slaughterhouse to investigate the effect of seasonal parameters on meat quality during the hot and cool seasons of Oman. The collection period (12 months) was divided into two seasons according to ambient temperatures and relative humidity and termed: Cool Season (November–March with average temperature of 21.2±1.40 °C and 57.9±1.61% relative humidity) and Hot Season (April–October with average temperature of 34.3±1.67 °C and 48.8±7.57% relative humidity). The season had a significant effect on meat quality characteristics of the LT muscle. Muscles collected during the hot season had significantly (P<0.001) higher ultimate pH values (6.24) with significantly (P<0.001) lower Warner–Bratzler (WB) shear force values (10.12) than those collected during the cool season (5.54 and 15.58). In these hot-boned samples, there was a linear relationship between ultimate pH and WB shear values. Cooking loss was significantly (P<0.001) higher for cool season samples (26.01%) than from hot season samples (19.75%). Beef from the hot season group had significantly (P<0.001) darker meat than that of the cold season group, based on L* (31.45 vs 35.58), a* (18.53 vs 23.19) and b* (4.16 vs 6.40) colour measurements. There was a linear relationship between ultimate pH and cooking loss, L*, a* and b*. These results indicated that heat stress (>30 °C) lead to physiological stress in beef cattle, which in turn increased muscle ultimate pH and influenced related meat quality characteristics.