M.A. Price

Blast chilling and low voltage electrical stimulation influences on bison (Bison bison bison) meat quality

Conventional carcass chilling is a lengthy and energy expensive process. Blast chilling (BL) can reduce cooling time and associated shrink loss, although its application may compromise meat quality, particularly in lean carcasses or those with localized finish such as bison. Low voltage electrical stimulation (LVES) can reduce the risk of decreased meat quality by inducing rapid rigor onset prior to exposure of the musculature to extreme cold temperature. BL (-20°C, 3 m·s(-1) air velocity, 2 h) accelerated temperature decline of bison Longissimus lumborum (LL) and significantly reduced cooler shrink loss versus conventional chilling (CONV: 0-2°C, 24 h). While BL tended to produce darker meat, this effect was tempered by the application of LVES, and samples from the combined treatment were significantly lighter than CONV. BL resulted in reduced tenderness in the LL, as assessed by shear force measurement, in part due to significantly shorter sarcomere length in BL samples. Taste panelists, however, were unable to detect a significant or detrimental BL effect. Where LVES was incorporated, there was an improved tenderness response with ageing. The combined LVES/BL treatment of bison carcasses is recommended for rapid processing without compromising meat quality.

Endurance-exercised growing sheep: I. Post-mortem and histological changes in skeletal muscles.

A study was conducted with Suffolk ram lambs to determine whether chronic endurance exercise would affect post-mortem changes in muscle tissue. Muscle fibre diameters, sarcomere lengths, fibre types, and pH and temperature declines were measured in five skeletal muscles (semimembranosus, SM: vastus lateralis, VL; semitendinosus, ST; psoas major, PM; gastrocnemius, G). The exercise had no significant effect on muscle size or muscle fibre diameter in any of the muscles studied. However, endurance-exercised sheep had significantly shorter sarcomeres in all five muscles than their non-exercised counterparts. The pH decline curves differed among muscles; those having the highest proportion of glycolytic fibres had the slowest rates of pH decline. The increased proportion of slow-twitch fibres in the SM, VL, ST and G associated with the exercise regime had little effect on the post-mortem pH decline. However, the ST also had a significant exercise-associated increase in the proportion of oxidative-glycolytic fibres (intermediate) and was the only muscle in which exercise influenced the rate of pH decline significantly.

Endurance-exercised growing sheep: II. Tenderness increase and change in meat quality

A study was conducted to examine the effect, in ram lambs, of chronic treadmill exercise, on meat quality. A secondary objective was to relate changes in tenderness to metabolic and chemical phonomena. Meat quality traits, including instrumental measurements of tenderness and thaw and drip losses, were recorded for two muscles from the hind limb (semimembranosus SM; vastus lateralis, VL). Chemical analyses, including total and soluble collagen, total and myofibrillar protein, and myofibrillar fragmentation were also performed. Muscles from exercised sheep were significantly more tender than muscles from their control counterparts. A larger myofibrillar protein to total collagen ratio was observed in the VL muscles from exercised sheep (P < 0·01) which probably contributed to the observed increase in tenderness. However, similar results were not observed for the SM muscle. The tendency for a slightly higher pH at similar post-mortem temperatures in meat from exercised sheep may also have contributed to the increased tenderness.

A mapping method for the description of Warner–Bratzler shear force gradients in beef Longissimus thoracis et lumborum and Semitendinosus

A novel approach to mapping Warner-Bratzler shear of whole muscles was explored. The procedure was used on the Longissimus thoracis et lumborum (LTL) and Semitendinosus (ST) from six beef cattle by first marking skeletally defined anatomical landmarks on the muscle in situ. After removal from the carcass, further divisions were made while preserving sample orientation during cooking and preparation for shearing. Shear gradients were observed in all planes of the LTL, particularly the medial-lateral. The mid-section of the ST had the lowest shears while superficial locations of the cross-section had greater values. Muscle comparison indicated the ST was more uniform than the LTL. The mapping technique was subsequently used to identify localized effects of altered carcass suspension on shear values and sarcomere length in the lumbar Longissimus from four beef cattle. This mapping method will provide guidance for further intensive investigation across the carcass musculature and under varying carcass conditions.

The influence of elevated temperature conditioning on bison (Bison bison bison) meat quality.

Elevated temperature conditioning (ETC: 10°C until 10 h post mortem) was effectively employed as a means of cooling bison carcasses in order to avoid the cold-induced meat quality defects that are a risk with conventional bison carcass chilling (0-2°C for 24 h). The ETC treatment maintained internal M. Longissimus lumborum and M. Semimembranosus temperature above 10°C within the first 10 h post mortem. The time/temperature combination did not result in significant evaporative loss, although loss of weight during carcass cooling can represent a practical economic loss. ETC accelerated post-mortem glycolysis and pH decline, and resulted in samples of lighter, more intense red colour than those conventionally chilled. Significant improvement in both initial tenderness and tenderization during ageing was realized with the use of ETC.

Relationships between beef carcass shape and muscle to bone ratio

Relationships between muscularity and muscle to bone ratio were investigated for beef carcasses of several breeds and crosses, and three genders using data from Bristol and Alberta. Side dissection data in terms of muscle, fat and bone weights were used to calculate muscle to bone ratios (MtoB) and muscularity indexes (MUSC) for the whole side or for the region around the femur bone. Highly significant breed and gender effects on MtoB and MUSC were shown for both the Bristol and the Alberta data sets, but the group differences for MtoB were not the same as those for MUSC despite the fact that these two characteristics were closely correlated. For both sets of data, for example, MUSC values at a common muscle plus bone weight were significantly higher for carcasses of bulls than heifers, but similarly adjusted MtoB values were generally higher for carcasses of heifers than bulls. Differences among breed groups were mainly in a similar direction for MUSC and MtoB, but the size of the differences varied widely. For example, relative to the Friesian, the Jersey breed had a significantly higher MtoB but a significantly lower MUSC, and carcasses of double-muscled bulls had a femur-region MtoB that was 19.2% greater than that of a group of Shorthorn-cross carcasses, but a MUSC that was only 1.7% higher. These findings show that because of the inconsistent relationships between muscularity and muscle to bone ratio among different classes of beef carcasses, lean meat yield cannot always be predicted without bias if measures of carcass shape are used as indicators of muscle to bone ratio.

The Influence of Cooking Temperature on the Eating Quality of Beef from Bulls and Steers Fed Three Levels of Dietary Roughage

Abstract The cooking losses and subsequent eating quality of semimembranosus (SM) roasts obtained from bulls and steers fed three levels of dietary roughage (20, 50 and 80 percent alfalfa-brome hay) were determined. Evaluations were conducted by dry heat roasting at 121°C and 163°C to 63°C internal temperature. Cooking losses of SM roasts were affected by cooking temperature, but not by level of dietary roughage or castration. Subjective evaluation by a trained panel indicated that SM roasts cooked at 121°C were significantly better in texture, softness, juiciness, flavor, tenderness, residual connective tissue and overall acceptability than comparable samples cooked at 163°C. Objective measurements of juiciness (water holding capacity) and tenderness for SM roasts supported the findings from sensory evaluations. Trained panelists indicated that SM roasts from animals on all roughage levels were similar in eating quality. There were no significant differences in water holding capacity (WHC), Warner Bratzler shear and penetrometer data attributable to roughage levels; Ottawa Texture Measuring System (OTMS) data indicated that samples from the 20 percent roughage group were more tender than those from the 80 percent roughage group. SM roasts from steers were subjectively rated significantly better in texture, tenderness and connective tissue than comparable samples from bulls; roasts from both “sexes” were similar in all other quality characteristics evaluated. Roasts from bulls had a greater WHC than those of steers. There were no significant differences in Warner Bratzler shear force values and penetrometer data attributable to sex; OTMS data indicated that SM roasts from steers were more tender (P

The Effect of Conventional and Microwave Cooking on the Eating Quality of Beef from Bulls of Three Differing Breed-Types

Abstract The effects of microwave cooking with intermittent energy application and of conventional electric heating on the cooking losses and eating quality of paired beef semitendinosus (ST) roasts were determined. The beef was obtained from young bulls, representing three breed-types: Hereford crossbred (HC), dairy crossbred (DC) and beef synthetic (SY), which had been fed and managed under similar conditions. Cooking time and cooking losses of ST roasts were affected by cooking method, but did not appear to be affected by breed. Subjective evaluation indicated that roasts from both cooking methods were similar in internal color, initial juiciness, softness, juiciness, flavor, residual connective tissue and overall acceptability but panelists rated roasts cooked conventionally significantly better in external color, evenness of internal color, texture and tenderness than those cooked electronically. Objective measurements of juiciness (water holding capacity (WHC), tenderness (Warner Bratzler shear, Ottawa texture measuring system (OTMS) with Warner Bratzler blade) and softness (penetrometer) for ST roasts agreed with findings for cooking method from sensory evaluations. Trained panelists indicated that ST roasts from all breeds were similar in eating quality. There were no significant differences in WHC, Warner Bratzler shear values. OTMS measurements and penetrometer data attributable to breed. Thus, these studies suggest that 1) ST roasts may be cooked using either conventional electric ovens or microwave ovens operated with intermittent energy application; and 2) beef obtained from the three breed-types of young bulls was similar and judged acceptable in eating quality.

Studies of extra low voltage electrical stimulation of mature beef carcasses

The quality characteristics of biceps femoris (BF) and semimembranosus (SM) roasts obtained from mature cow carcasses treated with a commercial extra low voltage (30 V) electrical stimulation (LVES) system were determined. LVES was applied for either 2 (ESII) or 4 min (ESIII). Evaluations were conducted on meat obtained from control sides (no ES) aged for either 48 h (Ia) or 7 days (Ib) and from ES sides aged 48 h. ES caused a reduction (P<0·001) in pH values at 2 and 6 h post mortem. At 24 h, the pH of muscles from all carcasses was about 5·5. ES duration did not influence muscle pH. Rib-eye muscle colour for ESII and ESIII carcasses was lighter and brighter (P<0·05) than that of control carcasses. Generally stimulated BF roasts had greater cooking losses than control Group Ib roasts; SM roasts from ES carcasses had lower losses than comparable to Group Ib roasts. ES duration had no effect on per cent cooking losses. Trained panelists generally detected few significant effects in BF roasts due to ES. Warner-Bratzler data indicated that ESII and ESIII BF roasts were similar and significantly more tender than comparable control Group Ib samples: OTMS data indicated that all BF roasts were similar in tenderness. However, SM roasts from ES carcasses were judged more soft (Groups II and III) and tender (ESII) than comparable control roasts. Instrumental measurements of tenderness for SM roasts tended to support the taste panel results. Generally, duration of LVES had no effect on the eating quality of either BF or SM roasts. Since LVES effects on the palatability of SM roasts were evident but the effects of stimulation of BF roasts were few, further studies of this LVES system are needed before its use can be recommended. Generally, increasing post-mortem ageing time for mature control carcasses did not influence either BF or SM roast quality.

The Influence of Roughage Level in the Finishing Diet on the Eating Quality of Beef from Bulls and Steers Slaughtered at Two Liveweights

Abstract Cooking losses and eating quality were determined for semitendinosus (ST) and longissimus dorsi (LD) roasts obtained from bulls and steers fed three levels of dietary roughage (20, 50 and 80% alfalfa–brome hay) and from animals slaughtered at approximately 450 or 580 kg liveweight. Cooking losses of either type of roast did not appear to be affected by level of dietary roughage, but were affected by castration. For either weight group, trained panelists generally determined no significant effects of roughage level on eating quality of either type of roast. However, consumer panelists noted significant differences in the flavor, tenderness, and overall acceptability but not juiciness in ST roasts with those from the animals fed 20% roughage superior to those from the 80% group. Objective measurements of juiciness (water holding capacity (WHC)) and tenderness generally supported the data of the trained panel. Only one objective test for each type of roast, rated roasts from animals fed 80% roughage to be significantly less tender than roasts from animals fed lower roughage levels. All other objective tests detected no differences in tenderness attributable to roughage level. Cooking losses were generally greater for roasts from bulls than from steers. Fat percentage was lower and moisture higher for roasts from bulls than those from steers. A detectable difference in pH, with bull samples higher than steer samples, was found for ST roasts from the heavy weight group, and for LD roasts from both slaughter weight groups. Trained panelists detected few differences in palatability characteristics between ST roasts from bulls vs steers; more differences were detected between bull and steer LD roasts, and the differences were greater for the heavy slaughter weight group. Consumer panelists rated steer ST roasts superior to those from bulls for flavor, tenderness and overall acceptability, but the rating of roasts from bulls was acceptable. Water holding capacity was similar for bull and steer roasts in this study. Objective tests for tenderness did not detect differences between bull and steer ST roasts but did show highly significant differences between bulls and steers for LD roasts. Objective color difference between sexes was found only for ST roasts from the heavy slaughter group. Thus these studies indicate that beef from animals fed roughage levels from 20 to 80% of the diet was similar and acceptable. Differences in eating quality of beef from bulls and steers were detected but generally these differences were small and beef from bulls was judged acceptable.