THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: I. PHYSICAL AND TEXTURAL PROPERTIES

A total of 60 bovine carcasses from crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two related experiments to evaluate the effects of delayed chilling and altered carcass suspension on certain physical and textural properties of beef muscle. Hip-free suspension (suspension by the os coxae from a hook inserted through the obturator foramen with the limbs hanging free) significantly (P<0.05) reduced the shear force values obtained on samples from the longissimus dorsi (LD) and semimembranosus (SM) muscles but had no effect (P>0.05) on shear force values obtained on samples from the psoas major (PM) muscle. The only other physical property affected by altered carcass suspension was objective measurement of lean color in the SM. Carcasses suspended from the aitchbone had darker SM muscles. Delayed chilling treatments had no effect (P>0.05) on 2-h SM pH values or 144-h pH values for any of the muscles studied. However, carcasses held at either 13°C or 22°C for 24 h had higher (P<0.05) SM pH values. When delayed chilling treatments affected muscle color, treated sides had darker lean than their conventinally chilled counterparts. Textural properties (shear values and taste panel tenderness ratings) and amount of expressible juice generally were unaffected by the delayed chilling treatments evaluated.     

Properties of Frankfurters Made From Electrically Stimulated Beef

Frankfurters (3 replications of 4.54 kg meat batches) were conventionally made. Paired sides from beef were used for control (NES) and electrically stimulated (ES) meats (clods, flanks and plates). All-beef frankfurters (100% ES beef or 100% NES beef) and beef-pork frankfurters (80% ES beef-20% pork or 80% NES beef-20% pork) were made. The pork was not electrically stimulated. Proximate composition within cut of beef (plate, flank, clod) was not affected (P > 0.05) by ES. However, ES clods had (numerically) greater percentages of expressible juice loss, greater percentages of salt-soluble protein and lower percentages of juice loss during cooking than did NES clods (not statistically different). Use of ES beef alone or in combination with 20% pork did not affect external visual color, off-flavor, overall desirability or processing shrinkage of frankfurters. ES may affect certain properties (raw and cooked muscles) as measured in the laboratory, but when these ES muscles are used to make frankfurters, no real advantages or disadvantages were suggested by this study.     

Effects of electrical stimulation on early postmortem muscle pH and temperature declines in pigs from different genetic lines and halothane genotypes

The objective of this study was to determine if electrical stimulation (ES) early postmortem is an effective method to generate PSE-like meat. One hundred and thirty-eight gilts (85-125 kg) from heavy muscled (HM), normal muscled (NM), and light muscled (LM) porcine genetic lines were subjected to one of two treatments: ES (26 pulses of 500 V, 60 Hz) at 3 min postmortem or non-stimulated (NS). Pigs from HM line were further characterized as halothane (HAL) carriers (Nn) or non-carriers (NN). ES carcasses had lower (P<0.0001) pH values and higher (P<0.0001) temperature than NS carcasses during the first 56 min postmortem. ES carcasses had lower (P<0.0001) a*-values, and color and firmness scores, as well as higher (P<0.0001) drip loss and L*-values. No significant interactions were found between treatment and genetic line or HAL gene status with regard to pH, temperature, or quality characteristics. Temperature and pH declines within the first hour postmortem were not affected by genetic line, but slight (P<0.01) quality differences were observed. Nn and NN did not differ in pH or temperature within the first hour postmortem, but Nn carcasses had lower (P<0.01) color and firmness scores, and higher (P<0.05) drip loss. These results show that ES early postmortem is an effective method for simulating PSE development in pigs of different muscling and HAL gene status, and suggest that pH and temperature decline alone cannot explain all aspects of pork quality.     

The effect of electrical stimulation on the quality of three bovine muscles

Meat bulls were randomly assigned to five treatment groups-intermittent electrical stimulation at 300 V (ES) at 5 min and 35 min post mortem (intact carcasses), 35 min post mortem (split carcasses) and non-stimulated controls (NS) (intact and split carcasses). Stimulated carcasses in all groups showed a significantly more rapid pH fall during the first 8h post mortem in adductor (AD), longissimus dorsi (LD) and triceps brachii (TB) muscles. Cooling rates were relatively slow. Samples were removed from the carcass at 24h post mortem. After vacuum storage at 3°C for 6 days stimulated muscles showed lower drip (LD and TB) and heating loss (TB), lower shear force values (AD, LD and TB) and higher taste panel scores (AD, LD and TB) compared with NS controls. No significant differences in tenderness were observed between the three ES groups. Sarcomere length assessment showed more contraction in NS carcasses, particularly in the superficially located LD and TB. These results suggest that cold shortening may occur in some muscles under cooling conditions so far considered safe in this respect. Since higher drip losses coincided with lower sarcomere lengths in these (NS) muscles, it is suggested that, under these conditions, ES may mask the increased drip losses which are possibly the result of muscle contraction. Furthermore, ES prevents the occurrence of cold shortening and, in addition, may exert some 'extra tenderising effect', which is not related to splitting of the carcass nor restricted merely to the LD muscle.     

Rapid chilling has no detrimental effect on the tenderness of low-voltage electrically stimulated M. longissimus in Chinese bulls

This study investigated the effect of pre-rigor rapid chilling (RC) on the rate of pH and temperature decline, shear force values and ultrastructure of M. longissimus from beef carcasses exposed to electrical stimulation (ES). Chinese bull carcasses were electrically stimulated, and the alternate sides of the carcasses either were chilled conventionally (CC, 0-4°C, air speed 0.5 m/s for 24 h) or they underwent RC (-14±1°C, air speed 3 m/s for 2 h and then cooled under CC conditions until 24 h post-mortem). The results showed that RC increased the rate of temperature decline (P<0.05) and decreased the rate of pH decline (P<0.05). There were no significant differences in the shear force value and sarcomere length of M. longissimus between the two treatments (P>0.05). The results of this study indicate that RC has no detrimental impact on the tenderness of beef carcasses exposed to ES.     

Early postmortem electrical stimulation simulates PSE pork development

Carcasses from 64 gilts were subjected to electrical stimulation (ES) at 3, 15, 25, 35, 45, and 55 min postmortem or were untreated (NS). Temperature and pH of longissimus muscles were recorded at 1, 7, 14, 20, 30, 40, 50, and 60 min, and 24 h postmortem. Muscle samples were collected at 1, 30 and 60 min, and 24 h for determining glycolytic metabolite concentrations. ES at 3, 15, and 25 min resulted in lower (P<0.05) muscle pH, but stimulation after 25 min had no effect on muscle pH. Likewise, ES prior to 25 min resulted in greater (P<0.05) muscle temperatures. Muscle lactate concentrations were greater (P<0.05) in carcasses stimulated before 45 min postmortem. Glucose 6-phosphate concentration decreased (P<0.05) during the first hr postmortem and increased (P<0.05) thereafter. ES of carcasses at 45 and 55 min resulted in higher (P<0.05) concentrations of muscle glucose 6-phosphate at 24 h compared with NS and early-stimulated carcasses. Muscle glycogen concentrations at 30 min in carcasses stimulated at 3, 15 and 25 min were lower (P<0.05) than NS carcasses. Carcasses stimulated at 3 and 15 min exhibited lower (P<0.05) concentrations of muscle glycogen at 60 min than NS carcasses. Carcasses stimulated at 3 and 15 min postmortem exhibited lower (P<0.05) color and firmness scores, while ES at 3 and 25 min postmortem resulted in lower (P<0.05) water holding capacity. ES had no significant effect on CIE L(?), a(?), b(?), or 24 h muscle pH. These data show that ES of pork carcasses during the first 25 min postmortem creates PSE-like quality characteristics and suggest that ES is a potential model for studying pork quality development.     

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.     

Use of electrical stimulation, hot processing and carrageenan for processing low-fat ground beef patties

Three studies were conducted to determine the effects of electrical stimulation, hot processing and carrageenan usage on sensory, shear force and cooking properties of low-fat (5, 10%) beef patties. The right or left sides of beef carcasses assigned to electrical stimulation (ES) received 600 V pulsating current for 120 s. Non-stimulated (NS) sides were also included for comparisons. Sides subjected to hot processing (HP) were boned 90 min post-exsanguination. Cold processing (CP) was initiated 48 h post mortem. Formulations for the manufacture of patties included the use of carrageenan [none, 0.5% iota (ι), 0.5% kappa (κ)]. Patties from NSHP beef had higher pH and cooking yields, less shrink in patty dimensions during cooking and lower shear force values than patties from NSCP controls (P < 0.05). ES improved tenderness and juiciness of CP patties, while ESHP patties exhibited higher cooking yields than NSCP patties. Tenderness was improved in two of the three studies as a result of increasing the fat content from 5 to 10%. Use of ι-carrageenan provided improvements in tenderness and juiciness over patties receiving no carrageenan or κ-carrageenan. Processors should consider HP with 1.0% added salt (improved cooking yields, patty configuration, tenderness) and the use of ι-carrageenan (improved tenderness and juiciness) for low-fat beef patties.     

Effects of temperature conditioning on postmortem changes in physico-chemical properties in Korean native cattle (Hanwoo)

The objective of this study was to examine the changes in physico-chemical properties that occur after adjusting postmortem chilling temperatures in Hanwoo beef. The right sides of beef carcasses were chilled for 4h at 2°C, 4h at 12°C and 16h at 2°C. The left sides were used as controls, chilled for 24h at 2°C. It took 8h for the control carcasses to cool down to <10°C and 10h 20min for the treatment. Adjusting the chilling temperature could be effective in lowering the postmortem pH and glycogen content. Treatment muscles at least 8h postmortem had longer sarcomeres than the control (P<0.05). The shear force in treatment carcasses at day 1 was similar to that of the control at day 6. Alternate chilling temperature had no detrimental effect on drip, cooking, total loss or color. Total numbers of aerobic plate counts were not significantly different between the control and treatment.     

Effects of Beef Carcass Electrical Stimulation and Hot Boning on Muscle Display Color of Polyvinylchloride Packaged Steaks

Ninety-six beef sides from 48 carcasses were used to determine the effects of control (C, chilled 48 hr at 5°C), electrical stimulation (ES, 45 min postmortem, 400 volts for 2 min, pulsed), hot boning (HB, 2 hr postmortem), and combination (ESHB) treatments on muscle color of longissimus (LD) and semimembranosus (SM) steaks packaged in polyvinylchloride film. LD from HB was mostly visually darker, had less oxymyoglobin, and more metmyoglobin than other treatments as was the SM, but SM had fewer differences between HB and ESHB. ES and ESHB muscles were visually similar, suggesting ES minimized the darkening effect of HB. Regardless of treatment, muscle color was acceptable at 0, 1, 3 and 5 days of display.     

Effects of Beef Carcass Electrical Stimulation and Hot Boning on Display Color of Unfrozen Vacuum Packaged Steaks

Ninety-six beef sides from 48 carcasses were used to determine effects of control (C, chilled 48 hr at 5°C), electrical stimulation (ES, 45 min postmortem, 400 volts for 2 min, pulsed), and hot boning (HB, 2 hr postmortem), and combination (ESHB) treatments on muscle color of longissimus (LD) and semimembranosus (SM), vacuum packaged steaks. HB muscles frequently were visually brighter purplish-red than other treatments. Compared to ESHB, ES LD was not different, but ES SM was duller purplish-red in color. Reflectance indicators of reduced myoglobin and metmyoglobin were essentially the same across treatments in both muscles. Vacuum packaged fresh beef steaks from all treatments were acceptable in color at 0, 3, 7, and 14 days of display. Vacuum packaging appears suitable for steaks from any of these carcass treatments but is especially useful for steaks from hot boned cuts.     

Effects of Beef Carcass Electrical Stimulation, Hot Boning, and Aging on Unfrozen and Frozen Longissimus dorsi and Semimembranosus Steaks

Ninety-six sides from 48 beef carcasses were used to study the effects of hot boning (HB), electrical stimulation (ES), a combination of electrical stimulation and hot boning (ESHB), and steak storage treatments on longissimus dorsi and semimembranosus steaks. Steak storage treatments were: unfrozen (aged until 6 days postmortem) or frozen (ES, HB, and ESHB frozen 24 hr and controls 48 hr postmortem). ES did not improve taste panel ratings or consistently lower shear force values when compared with control counterparts. Storing carcasses at 5°C for the first 24 hr postmortem and freezing ES steaks at 24 hr versus 48 hr postmortem for the control possibly diluted the effectiveness of ES. However, ES did eliminate any toughening due to HB.     

Response of bovine muscles to direct high voltage electrical stimuli

Left sides of beef carcasses were stimulated (ES) using multiple-contact electrodes for both the positive and negative electrodes. These electrodes were attached to the carcass side in the neck and shoulder (arm) region (positive electrodes) and the hindquarter (round) region (negative electrodes). Stimulation was generated using 600 V, 60 Hz, 2·8 A alternating current for a duration of 2 min (impulses: 2 s on and 2 s off). Right sides served as controls. Carcass sides were chilled at 2°C. Stimulated sides showed a more rapid pH fall during the first 5 h post-stimulation in the longissimus dorsi, semimembranosus, semitendinosus, biceps femoris and triceps brachii (long head) muscles. Lower shear values for muscles in direct contact with the ES electrodes were observed compared to controls, except in the case of the semitendinosus muscle, where no difference was found. Data from the present study suggest that muscles, which quite often do not respond to ES and do not exhibit an improvement in tenderness, perhaps because they may not be located in the current pathway, can show improvements in tenderness if the current is distributed in the direction of these muscles. However, a muscle's response to the electrical stimuli, with the accompanying rapid decline in pH, does not necessarily ensure a significant improvement in tenderness.     

Reducing Postmortem Aging Time of Beef with Electrical Stimulation

Two studies (Study 1 = 23 forage-fed steers; Study 2 = 20 grain-fed steers and heifers) were conducted to determine relationships of electrical stimulation (ES) and/or postmortem aging (PA) to tenderness of beef. For Study 1, steaks from ES sides had lower (P < 0.05) Warner-Bratzler shear (WBS) values than steaks from not-ES sides for each PA period. In addition, the percentage reduction in WBS values was greater for the steaks from the ES-Day 2 group (–29.5%) than for steaks from even the longest PA period (14 days) from the not-ES group (–25.8%). For Study 2, during the fist three PA periods (1, 2 and 5 days), ES resulted in more desirable (P < 0.05) flavor ratings (Day l), higher (P < 0.05) tenderness ratings and lower (P < 0.05) WBS values (Day 1, 2, 5) and more desirable (P < 0.05) overall palatability ratings (Day 1, 2). During the last three PA periods (8, 11 and 14 days), ES resulted in higher (P < 0.05) tenderness ratings (Day 8), lower (P < 0.05) juiciness ratings (Day 11, 14) and lower (P < 0.05) WBS values (Day 8). Based on these results, ES had the greatest impact on beef palatability if the period of aging was 8 days or less; with additional aging time, ES effects on palatability were negated. When each treatment (ES, not-ES) was divided into two groups based on median tenderness ratings for the not-ES group, ES had the greatest impact on those carcasses in the “tough” group while ES had little impact on those carcasses in the “tender” group. ES will accelerate the postmortem aging of beef but the aging time reduction and extent of ultimate tenderization appears to be affected by the inherent tenderness of the beef.     

Characterization of beef semimembranosus and adductor muscles from US and Mexican origin

The purpose of this study was to compare the chemical composition and sensory characteristics of two beef muscles (semimembranosus, SM and adductor, AD) from the inside round of Mexican and US origins. Inside rounds were obtained from 20 Mexican bull carcasses, representing beef of Mexican origin. Forty-vacuum packaged USDA Choice and Select inside rounds were purchased from a local trader, representing US beef. Muscles were analyzed for chemical composition, Warner-Bratzler shear force (WBSF), cooking loss percentage, instrumental color, textural profile, and consumer acceptability. Muscles imported from the US contained more intramuscular fat, had higher cooking loss percentages, lower shear force values, and higher consumer ratings for overall desirability than Mexican counterparts (P<0.05). Choice and Select beef samples had similar WBSF values (P>0.05). Consumers found differences in juiciness and tenderness ratings between the two muscles, with the SM being tougher and less juicy than the AD (P<0.05).     

Characteristics of Pre-Rigor Pressurized Versus Conventionally Processed Beef Cooked by Microwaves and by Broiling

Eighty-six grams paired beef semitendinosus portions processed either conventionally or by pre-rigor pressure were broiled or microwave cooked. Pre-rigor pressure-treated cooked beef portions were higher (P < 0.05) than untreated portions in total moisture, pH, exterior color a+ values and subjective tenderness and ease of fiber separation scores than did the untreated portions. Total moisture, drip cooking loss, interior a+ (redness) color value, and exterior L (lightness) and b+ (yellowness) color values were significantly higher in the microwaved beef portions as compared to the broiled portions. Neither juiciness nor flavor of samples were influenced (P < 0.05) by treatment or by cooking method.     

Muscle profiling: Characterizing the muscles of the beef chuck and round

To fully characterize properties of the muscles of the beef chuck and round, and to reveal potential opportunities to upgrade the value, 39 different muscles were dissected from 142 beef carcasses differing in carcass weight, yield grade, and quality grade. Numerous physical and chemical properties of the muscles were determined. Muscle effects were observed for all traits (objective color, expressible moisture, proximate composition, emulsion capacity, pH, total collagen content, total heme-iron concentration, and Warner-Bratzler shear force). USDA quality grade generally had the most effect on muscle traits, with carcass weight and yield grade having lesser effects. These muscle profile data will allow for more informed decisions to be made in the selection of individual muscles from the beef chuck and round for the production of value-added products.     

EFFECTS OF POSTMORTEM TIME AND ELECTRICAL STIMULATION ON HISTOCHEMICAL MUSCLE FIBER STAINING AND pH IN THE MIDDLE GLUTEAL MUSCLE FROM BEEF CATTLE

The purpose of this study was to investigate the histochemical staining properties of the myosin ATPase (pH 9.4) and succinate dehydrogenase (SDH) stains as functions of muscle for electrical stimulation and postmortem time. Muscle blocks, 2 cubic centimeters in volume, were removed from the gluteus medius of five electrically stimulated (ES) and five nonstimulated (NS) contralateral beef carcass sides at 0, 2 and 24 h after stimulation. The pH of the gluteus medius decreased significantly in both the ES (5.86) and NS (6.14) sides within two hours postmortem and the 24 h pH values were 5.76 and 5.72, respectively. Muscle histochemical staining characteristics for myosin ATPase (pH 9.4) did not change (P > .05) within 24 h postmortem for either ES or NS muscle. A change in the staining characteristics for SDH was found for both ES and NS at 24 h postmortem. No difference in histochemical staining characteristics was found as a result of ES.     

COMBINED EFFECTS OF ELECTRICAL STIMULATION, CARCASS POSTURE AND INSULATED BAGS ON RAM LAMB TENDERNESS

Thirty-six ram lambs fed a high roughage diet from weaning to 6 months of age and 48 kg body weight at slaughter were assigned randomly to six postmortem (PM) treatments: (1) control; (2) carcasses placed in insulated bags (B) for 24h PM; (3) carcasses suspended via the coccygeal vertebrae (P); (4) electrical stimulation (ES); (5) ES combined with B for 24 h PM; and (6) ES combined with P for 1.5 h poststimulation then suspended via the achilles tendon. Stimulation improved shear values for the longissimus and rectus femoris muscles. Method B without ES reduced shear values for the Longissimus, Semimembranosus, biceps femoris and rectus femoris. Use of method P without ES reduced shear values for the longissimus and semimembranosus. Combining ES with method B reduced shear values for all the muscles evaluated. Similar results were found when combining ES with method P.     

Effects of Electrical Stimulation, Temperature of Boning and Storage Time on Bacterial Counts and Shelf-Life Characteristics of Beef Cuts

Strip loins and eye of rounds from 16 beef carcasses were used to study the effects of electrical stimulation (ES), no stimulation (NS), hot-boning (HB), and cold-boning (CB) on bacteriological and shelf-life evaluations. Following 7 days of vacuum-packaged storage, coliform counts were higher in the drip fluid from strip loins and lean surfaces of eye of rounds from ES compared to NS carcasses. A major advantage for HB in this study was the additional time required in retail display before the occurrence of lean surface discoloration. A previously identified benefit of lighter lean color with ES beef in carcass and primal cut form was also found in this study during display of retail cuts.