Effects of rate of pH fall, time of deboning, aging period, and their interaction on veal quality characteristics.

Three groups of veal carcasses were selected on the basis of their pH in the longissimus lumborum muscle at 3 h postmortem (pH3) to study the effects and interaction with time of deboning on quality characteristics of veal. The following groups of 10 calves each were selected: 1) fast pH fall, pH3 < 6.2; 2) intermediate pH fall, 6.2 < pH3 < 6.7; and 3) slow pH fall, pH3 > 6.7. Longissimus thoracis et lumborum (LTL) muscles of sides of the selected carcasses were randomly assigned to be excised at either 24 or 48 h postmortem. Color, water-holding capacity, and shear force measurements were determined after an aging period of 2, 3, 4, 7, and 14 d, respectively. Color of longissimus muscle samples from veal calves with similar preslaughter blood hemoglobin values becomes significantly lighter with a faster pH fall. Muscle color was not affected by time of deboning and overall color of all longissimus samples remained stable during storage and was not affected by rate of pH fall and time of deboning. Cooking losses increased with both a faster rate of pH fall and by deboning at 24 h postmortem. Drip losses during vacuum storage were higher for muscles excised at 24 rather than 48 h postmortem. Both when deboned at 24 and 48 h, postmortem veal carcasses with a lower rate of pH fall had higher shear force (SF) values than did carcasses with a higher rate of pH fall. Deboning at 24 h postmortem resulted in higher SF values than deboning at 48 h postmortem. Differences in SF between 24- and 48-h deboning were larger in slower glycolyzing carcasses. Aging improved tenderness but did not fully reduce the difference in SF values between 24- and 48-h deboning. The results suggest that deboning of veal carcasses before the ultimate pH has been reached may result in muscle contraction, which may exert negative effects on tenderness and water-holding capacity of veal. Effects of time of deboning can, at least partly, be explained by differential effects on shortening of the muscle fibers.

Proteolysis and tenderisation in reindeer (Rangifer tarandus tarandus L.) bull longissimus thoracis muscle of varying ultimate pH.

Proteolysis and tenderisation in reindeer (Rangifer tarandus tarandus L.) M. Longissimus Thoracis were studied. Mm. Longissimus ( the part cut out between vertebrae thoracales 6-7 and vertebrae lumbales 5-6) from 12 reindeer bulls (age 1 1 2 years) were, after ultimate pH and temperature measurements, excised and then sampled at various times post mortem for determination of sarcomere length, Warner-Bratzler shear force, calpain and calpastatin activities, cathepsins B + L activities, active site titration of cystatin-like inhibitors, myofibrillar protein degradation, collagen content and heat solubility. Upon measurement of ultimate pH, the carcasses were divided into two pH groups; normal pH (5.65 ≤ pH ≤ 5.79) and high pH (pH ≥ 5.80). Temperature and pH fall were relatively rapid in all reindeer carcasses. Sarcomere lengths tended to be shorter in the carcasses of the high pH group. In the three carcasses with the highest ultimate pH values (6.11, 6.34 and 6.38), sarcomere lengths were around or below 40% of resting length (1.37µm, 1.25µm and 1.25µm, respectively) which is likely associated with the occurrence of heat shortening. Total collagen content was higher and heat solubility lower in the high pH group, which could have masked differences in tenderness. However, all reindeer longissimus muscle samples were found to be extremely tender regardless of ultimate pH. By 3 days post mortem Warner-Bratzler shear force values were varying between 2.1-4.9 kg cm(2). There was a significantly higher activity of µ-calpain in the high pH group at 1 day post mortem. No differences in shear force, myofibrillar protein degradation as observed by SDS-PAGE, m-calpain and calpastatin activities, calhepsins B+ L activities or the levels of cystatin-like inhibitors were found between the two pH groups.

Effect of pelvic suspension and cooking temperature on the tenderness of electrically stimulated and aged beef, assessed with shear and compression tests.

Electrically stimulated carcass sides of young bulls were suspended at 1 hr post mortem from the aitch bone (pelvic suspension; PS) and Achilles tendon (AT), respectively. After an ageing period of 14 days at 3 °C, shear force (SF) and compression (20 and 80% compression) tests of the Mm. longissimus lumborum et thoracis (LO) and semimembranosus (SM) were conducted in raw muscle and after heating for 1 hr at 55, 60, 65, 70 and 80 °C. Collagen content was higher in SM than in LO, while sarcomere length (SL) of raw muscle were 1.75 and 1.78, for LO and SM. In comparison with the AT-side, PS increased SL by 21 and 47% and cooking loss (at 80 °C) by 2 and 6% for LO and SM, respectively. Drip loss of whole muscles from the PS-side during the ageing period tended to be lower (n.s.). Over the whole cooking temperature range, SF-values were relatively high for the SM in comparison with LO. For both muscles from the AT-side, the lowest SF-values were observed at 60 and 65 °C. The PS-treatment resulted in higher SF- values for raw muscle and after cooking at low temperatures (55 and 60 °C), particularly in the SM. In the intermediate temperature range (65 and 70 °C), PS had no significant effect, while in the higher temperature range (80 °C), SF-values were lower in the PS-side. Similar tendencies were observed in the LO, although the lower SF-values for the PS-side were observed already at 60 °C. In non-destructive compression (20%), there was a gradual increase in stress values with increasing cooking temperature. In comparison with the AT-side, the PS treatment resulted in the LO in similar or higher, and in the SM in lower stress values. With destructive compression (80%), PS resulted in SM in higher stress values in raw muscle and at 55 °C, in accordance with the SF-values. It is suggested that the higher SF- and 80% compression values in raw muscle and at low cooking temperatures, are caused by an increase in collagen strength due to a change in the direction and spatial organisation of the collagen fibres as a result of stretching of the muscle. This study demonstrates that the relative contributions of the collagen and myofibrillar components to the mechanical assessed toughness, as well as the effect of pelvic suspension, is dependent of muscle, cooking temperature and the mechanical test applied.

Post-mortem variation in pH, temperature, and colour profiles of veal carcasses in relation to breed, blood haemoglobin content, and carcass characteristics.

A total of 1764 male calves of the Meuse-Rhine-Yssel (MRY) and Friesian-Holstein (FH) breeds were slaughtered at two commercial slaughterhouses to investigate the variation in pH, temperature, and colour of Dutch veal carcasses processed without electrical stimulation and with a moderate chilling regimen (average temperature of the longissimus lumborum muscle at 45 min, 3, 24, and 48 h post-mortem was 38.4, 23.3, 3.7 and 1.9°C, respectively). Blood haemoglobin content was determined 2 weeks before slaughter. The efficacy of captive bolt stunning was scored and the carcass movements after shackling registered. Temperature and pH measurements were carried out at 45 min, and 3, 24, and 48 h after slaughter in the longissimus lumborum muscle (LL). Muscle surface colour (CieLAB-values) was measured with a colorimeter at the rectus abdominis muscle at the same times post-mortem. Carcass conformation and visual carcass colour classification were determined at 45 min post-mortem. Carcasses with a better EUROP-conformation score and heavier weight showed a higher rate of pH decline and a slower cooling rate. Slight differences in cooling systems between the slaughterhouses caused marked differences in pH and temperature profiles. Significant differences in carcass weight were observed between the MRY and FH breeds, leading to significant differences in pH and temperature profiles. Carcass colour of the two breeds was similar. Veal carcass colour in general was not related to the observed variation in post-mortem pH and temperature in the longissimus lumborum muscle and was shown to be more associated with the blood haemoglobin content. Haemoglobin content of the blood in the period before slaughter was shown to be related to the visually assessed carcass colour at 45 min post-mortem (using a 10-colour scale), as well as to the instrumentally determined L*-value, with significant correlation coefficients of 0.61 and -0.61, respectively. Repeated captive bolt stunning to obtain unconsciousness significantly decreased pH at 3 h post-mortem. The degree of carcass movement after slaughter did not influence pH, temperature, or colour profiles of the carcasses.