Effects of Electrical Stimulation and Hot Boning on Functional Characteristics of Preblended Beef Muscle in Model Systems

Thirty beef carcasses were used to determine the effects of electrical stimulation (ES) and hot boning on the emulsifying capacity (EC) and thermal emulsion stability (TES) of preblended Triceps brachii (TB) muscle (long head) from sides assigned to one of four treatments: (1) conventionally boned after chilling at 2–8°C until 48 hr postmortem (CB); (2) hot boned at 1 hr postmortem (HB); (3) ES during bleeding and conventionally boned at 48 hr postmortem (ESCB); and (4) ES during bleeding and hot boned at 1 hr postmortem (ESHB). HB preblended samples had greater EC and TES values than CB preblended samples in both nonstimulated (P < 0.05) and stimulated carcasses. When compared to nonstimulated sides, ES decreased (P < 0.05) these values in both ESHB and ESCB sides.     

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.     

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.     

Processing Properties of Beef Semimembranosus Muscle as Affected by Electrical Stimulation and Postmortem Treatment

Semimembranosus muscles from paired sides-electrically stimulated (ES) and not-stimulated (NES)-of mature cows were used to determine effects of certain postmortem treatments (state of rigor/temperature) and of ES on processing properties. ES decreased (P<0.05) pH values for prerigor, prerigor/frozen and postrigor/frozen muscles, but did not affect (P>0.05) values for total protein or juice loss during cooking. State of rigor/temperature treatment affected pH and salt-soluble protein (SSP) values more than did ES treatment. pH values differed (P<0.05) between each state of rigor/temperature treatment for both ES and NES samples. Salt-soluble protein values were higher (P<0.05) for NES prerigor than for NES postrigor/frozen samples and higher (P<0.05) for NES postrigor than for NES postrigor/frozen samples. SSP values for ES muscles were higher (P<0.05) for ES postrigor samples than for ES postrigor/frozen samples but were not different for other comparisons. Regardless of ES treatment, freezing of semimembranosus muscles increased pH values (P<0.05) and decreased SSP values (P<0.05) in three of four comparisons.     

WATER-HOLDING AND COLOR CHARACTERISTICS OF BEEF FROM ELECTRICALLY STIMULATED CARCASSES

Electrical stimulation (ES) was applied to the right sides of 15 beef carcasses and the corresponding left sides were used as nonstimulated (NS) controls. Data collected included: postexsanguination pH (0.5, 3, 6, 24 h), L, a, and b color values, drip loss, and expressible moisture. Muscles from ES carcasses tended to have more accelerated postmortem pH declines than the corresponding muscles from NS carcasses. M. triceps brachii had a lower pH at 0.5 h (P < 0.05) , M. longissimus thoracis had a lower pH at 0.5 h (P = 0.055) and 3 h (P < 0.05), and M. semimembranosus had a lower pH at 0.5 and 3 h (P < 0.05), respectively. Hunter L, a, and b values did not differ within ES and NS treated muscles. Additionally, ES did not influence color values of the M. semimembranosus. ES did not affect drip loss or expressible moisture in beef muscles.     

Effects of Electrical Stimulation, Aging, and Blade Tenderization on Hot-Boned Beef Psoas major and Triceps brachii Muscles

Forty-six steer carcasses were used to evaluate shear force values (SFV) for triceps brachii (TB) and psoas major (PM) muscles from sides assigned to three treatments: (1) chilled at 2–4°C for 48 hr (C); (2) hot boned 2 hr postmortem (HB); and (3) electrically stimulated 1 hr postmortem and hot boned 2 hr postmortem (ESHB). Some steaks were cut and frozen immediately after muscle excision or after 6 days of aging, and some were blade tenderized. HB and ESHB steaks had equal or smaller SFV relative to C after aging the TB and PM muscles; however, this was not true when TB steaks were cut after muscle excision. Electrical stimulation or blade tenderization did not improve HB.     

Low-voltage Electrical Stimulation Effects on Proteolysis and Lamb Tenderness

Lamb carcasses were subjected to low‐voltage electrical stimulation (ES; 28 V, 60 Hz) within 5 min postmortem (PM). After ES, the longissimus thoracis (LT) and semimembranosus (SM) muscles were removed to investigate subsequent biochemical changes. The pH values of the ES muscles declined rapidly until the 1^st 3 h PM (p < 0.05). The activities of μ‐calpain and calpastatin in ES muscles decreased significantly after 10 h PM (p < 0.05). Both ES LT and SM muscles tended to have lower shear‐force values, which suggested ES might accelerate activation of calpains as well as glycolytic rate, thereby improving muscle tenderness. Differences in thin and troponin‐T degradation between treatments were also observed with time PM.     

EFFECT OF ELECTRICAL STIMULATION ON THE BOVINE CARCASS

Six grain-fed steer carcasses with weights ranging from 163 kg to 232 kg were randomly assigned to low voltage electrical stimulation (45 V., 1.5 A., pulsation cycle of 1.5 s for duration of 150 s) or no stimulation treatments. The longissimus dorsi (LD) and semitendinosus (ST) muscles were studied using high temperature (12 h at 32° to 39°C, then 36h at -2° to 0°C) and low temperature (36 h at -14° to -12°C) periods. Shear force, cooking loss, drip loss and taste panel data were taken. Shear force data indicated that differences (P < 0.05) existed between electrically stimulated and nonstimulated hot boned LD and ST muscle. Statistical differences (P < 0.05) in drip and cooking losses were detected. The duo-trio test indicated that panelists were able to detect a difference between electrically stimulated (ES) and nonstimulated muscle (P < 0.05). Preference tests indicated that panelists were also able to detect a difference between chill and delay chill. Ratings showed that a statistical difference was detected between ES and hot processed muscles.     

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.     

Chemical and Physical Characteristics of Beef Chuck Muscles: Effect of Electrical Stimulation, Hot Boning and High Temperature Conditioning

Chucks from 12 electrically stimulated steer carcasses were randomly assigned to one of 3 treatments: (1) cold boned [CB], (control), (2) hot boned [HB], and (3) hot boned/time conditioned [HB/TC], (5 hr at 18°C). Infraspinatus, Serratus ventralis, Subscapularis, Supraspi-natus, Teres major, and Triceps brachii were excised from each chuck according to treatment conditions. No differences (P > 0.05) were noted among treatments for muscle yields, cooking loss, proximate composition, or collagen content; however, differences (P<0.05) were found among muscles. Differences (P < 0.05) were found among treatments and muscles for ultimate pH, sarcomere length, Warner Bratzler shear values, and Hunter color ‘a’ values. Sarcomere length of muscles assigned to CB treatment were longer (P < 0.05) than HB and HB/ TC treatments.     

Quality, palatability and weight loss of pork as affected by electrical stimulation

Forty-five swine (n = 15, stress-susceptible pigs, fasted for 18 h; n = 15, normal pigs, fasted for 48, 60 or 72h; n = 15, normal pigs, fasted for 18 h) were slaughtered. One side of each pig was electrically stimulated (ES)-550 V, 2-6 A, seventeen impulses, 1·8 s on and 1·8 s off per impulse-and the opposite side was not stimulated (NS). Ham and loin temperatures were monitored at 12 and 24 hours post mortem. Carcass quality-marbling, loin eye colour, loin eye firmness, subcutaneous fat firmness and belly firmness-was evaluated at 24 hours post mortem. Sides were fabricated into four lean cuts at 48 hours; cuts were placed on open metal racks in a 2°C cooler and weight loss was measured after 24, 48 and 72 hours storage. At 120 hours post mortem, loin chops were cut, frozen (-24°C for 45 days) and subsequently used to determine thaw loss, cooking loss, Warner-Bratzler shear (WBS) force and palatability. Ham temperatures (12 h) were significantly (P < 0·05) lower for the ES sides from the stress-susceptible, short-fast (SSF) group but not for normal, long-fast (NLF) or normal, short-fast (NSF) groups. ES produced lighter coloured, softer loin eyes in the SSF group but darker coloured, firmer loin eyes and firmer subcutaneous fat in the NLF group. No significant differences (P > 0·05) were detected for thaw loss, cooking loss, palatability ratings or WBS values between ES and NS in the SSF group but chops from ES sides of NLF animals had significantly (P < 0·05) higher ratings for muscle fibre tenderness, overall tenderness and overall palatability. Weight losses of the lean cuts from the ES sides were higher (P < 0·05) than those from NS sides in only three of sixty comparisons of cuts from the three groups of swine. These data suggest that ES had very minimal effects on quality, palatability or weight loss of pork.     

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.     

Concentration of Creatine Phosphate, Adenine Nucleotides and Their Derivatives in Electrically Stimulated and Nonstimulated Beef Muscle

The concentration of creatine phosphate (CP), adenosine tri-, di- and monophosphate (ATP, ADP and AMP, respectively), inosine monophosphate (IMP) and inosine in longissimus muscle removed from electrically stimulated (ES) and nonstimulated (NS) beef sides was enzymatically determined. After aging the carcass 7 days, steaks were removed for flavor evaluation. R values (absorbance ratios) were obtained from muscle samples removed over time from both sides. Data indicate more rapid catabolism of CP, ATP, and ADP in ES samples, with subsequent fluctuations in IMP and inosine concentration. At 12 and 24 hr post-stimulation, ES samples had more inosine; however, this difference did not exist after aging. Flavor differences were not observed after the 7-day aging period. R values parallel the degradation of adenine nucleotides and indicate rapid onset of rigor mortis in ES muscle.     

Physical and sensory attributes of hot-processed and conventionally chilled hams and bellies from electrically stimulated and non-stimulated pork carcasses

Forty-eight fresh hams and bellies were obtained from 24 market weight hogs (x = 94·5 kg) of which twelve were electrically stimulated (ES) by pulsing current immediately after exsanguination. The left side of each non-stimulated (NS) carcas was fabricated after conditioning for 3h post mortem at 17°C (NS hot-processed). The left sides of ES carcasses were fabricated 1 h pm. The right sides were fabricated following a 24 h cooler chill at 2°C (conventionally chilled: CP). Hams from ESCP carcasses had higher (P < 0·05) smokehouse yields than hams from NS carcasses. Hams that were hot-processed had higher smokehouse yields than the NSCP hams. Time of fabrication (1, 3 or 24h post mortem) did not affect smokehouse yields. Conventionally chilled bellies obtained from ES carcasses showed higher (P < 0·05) residual nitrite levels than those front electrically stimulated hot-processed (ESHP) carcasses. No differences were found for residual nitrite levels in the non-electrically stimulated sides. Panelists were unable to detect any sensory differences from the bacon strips. Sensory scores of ham slices were more juicy for non-stimulated hot-processed carcasses (NSHP) than those from ESHP carcasses. Panelists found the ham slices from NSCP carcasses to be more tender (P < 0·05) than those from electrically stimulated cold-processed (ESCP) carcasses. Results from this study clearly indicated that hot-processing of pork can provide hams and bellies that are acceptable for the production of cured hams and bacon of comparable quality and yield to those currently being produced under conventional processing methods.     

Effects of Electrical Stimulation and Delayed Chilling of Beef Carcasses on Carcass and Meat Characteristics

A 2x2 factorial experimental design with 2 replications was used to study the effects of a combination of electrical stimulation and delayed chilling of carcass on meat characteristics. Twenty Standard or Good grade beef cattle were slaughtered and 10 sides were assigned to each of the 4 treatments. Meat characteristics were evaluated subjectively (sensory panel evaluation) and objectively (W-B shear device). Electrically stimulated carcasses cooled faster in the first hour postmortem; thereafter the order of further cooling was reversed. The 24 hr postmortem weight loss in the electrically stimulated with delayed chilling did not differ (P > 0.05) from those receiving electrical stimulation plus immediate chilling nor those not stimulated but chilled immediately. For delayed chill carcasses, 24 hr postmortem weight loss was lower (P < 0.05) in electrically stimulated than in nonstimulated groups. Electrical stimulation reduced (P < 0.05) cooking losses. The difference in sarcomere lengths among the 4 treatments was not significant (P > 0.05). At the microstructural level, an open triad and T-system were observed immediately following electrical stimulation. As early as 24 hr postmortem, considerable Z-line degradation was observed in the electrically stimulated and delayed chilled samples.     

EARLY POSTMORTEM SKELETAL ALTERATIONS EFFECT ON SARCOMERE LENGTH, MYOFIBRILLAR FRAGMENTATION, AND MUSCLE TENDERNESS OF BEEF FROM LIGHT-WEIGHT, BRANGUS HEIFERS

Approximately 2 h after exsanguination, two skeletal cuts (TC) were made on randomly selected sides from 13 light-weight, Brangus heifers; companion sides served as untreated controls (C). After a 24-h chill period, four muscles (Longissimus muscle from the IMPS#112A ribeye roll, LT, and from the IMPS#180 strip loin, LL; Biceps femoris, BF; Semitendinosus, ST; and Semimembranosus, SM) were excised from each side, vacuum-packaged, and aged for 7 days. Five 2.54-cm thick steaks were cut from each of the muscles to determine the effectiveness of the TC treatment on sarcomere length (SL), myofibrillar fragmentation index (MFI) and cooked beef tenderness. The LT and LL steaks from TC-carcasses had longer (P < 0.05) sarcomeres, and the TC treatment decreased (P < 0.05) Warner-Bratzler shear (WBS) force values for the LT and LL by 35.8 and 33.2%, respectively. Moreover, SL of the muscles from the round were also increased (P < 0.05) by the TC procedure, but WBS force values were not different (P > 0.05) from C. Muscles from the TC sides had similar (P > 0.05) MFI values to those from control sides. This study demonstrated that the TC procedure, when applied 2 h postmortem, can effectively improve cooked beef tenderness of the Longissimus muscle .     

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.     

Effect of low-voltage electrical stimulation after dressing on color stability and water holding capacity of bovine longissimus muscle

The effect of low voltage electrical stimulation after dressing (ES) on color stability and water holding capacity (WHC) of beef was investigated. Nine Swedish red cattle were slaughtered and the left side was electrically stimulated (80 V, 35 s) approximately 30 min after stunning, whereas the other side was not treated and used as control. Color and its stability, WHC, and protein solubility were evaluated on longissimus lumborum muscles from the two sides. ES produced a brighter red color at 24h mainly by increasing the oxygenation capacity of myoglobin (P<0.01), which was attenuated by postmortem aging. ES did not affect WHC, protein solubility and color stability (P>0.05). Therefore, this technology could accelerate meat tenderization without any negative effect on commercial attributes, such as color or drip of bovine longissimus muscle.     

Effects of medium-voltage electrical stimulation on postmortem changes in fat-tailed sheep

Abstract: Effects of different medium‐voltage electrical stimulation (ES) and ageing on postmortem changes in longissimus dorsi muscle of the fat‐tailed sheep were studied. Fifteen male animals were divided into 5 equal groups (n= 3) including: T₁ (control, without ES), T₂ (100 V/30 s), T₃ (100 V/60 s), T₄ (150 V/30 s), and T₅ (150 V/60 s) with fixed frequency of 50 Hz. Five minutes after sticking, the carcasses were stimulated in order of the treatments. After normal processing, they were kept at 6 °C for 14 d. ES accelerated the glycolytic rate resulting in a significant fast fall in pH (P < 0.05) during the 1st 6‐h postmortem (PM) with a gradual decline until 24‐h PM, and a simultaneous significant reduction in adenosine triphosphate (ATP) content (P < 0.05). There was a significant (P < 0.05) decline in the total calpain activity during the 1st 6‐h PM. The muscles from ES carcasses had significantly (P < 0.05) lower water holding capacity (WHC) than those from nonstimulated ones. Ageing revealed a significant (P < 0.05) effect on the reduction of WHC. No significant difference was found for the mean value of the muscle color (L*, a*, and b*) in all treatment groups during ageing (P > 0.05). The results of free amino acid (FAA) content and myofibrillar fragmentation index (MFI) revealed a significant improvement of proteolysis and tenderness by ES and ageing (P < 0.05). In the present study, higher voltage/duration (150 V/60 s) showed greater effects and significantly accelerated glycolysis, pH decline, and ATP depletion and thus decreased the time for rigor completion and improved the tenderness.     

EFFECTS OF ELECTRICAL STIMULATION AND SUBPRIMAL STORAGE TIME ON PALATABILITY OF HOT-BONED BEEF

Sides from 33 forage-fed steers were electrically stimulated and hotboned (ESHB) and muscles were vacuum-packaged either within 2 h (17 sides) or at 24 h (16 sides). Opposite sides were not electrically stimulated and were cold-boned (NESCB) and vacuum-packaged at 24 h. For ESHB muscles, packaging time did not affect (P<0.05) palatability. Longissimus steaks from ESHB sides (pooled across packaging treatments) had lower (P<0.05) shear force values than steaks from NESCB sides. As storage time of muscles increased from 7 to 21 days, shear force values generally decreased. Combining electrical stimulation with hot-boning enabled the removal of muscles without detrimental effects on beef palatability.