Effects of Electrical Stimulation, Hot Boning and Chilling on Bull Semimembranosus Muscle

Taste panel, Warner-Bratzler shear force (WBS) and cooking loss characteristics of semimembranosus (SM) muscles from thirty electrically stimulated and hot-boned (ESHB) or control young bull sides were evaluated. At 2 hr postmortem, muscles were excised from electrically stimulated sides and chilled in a tray or in a cardboard box. All control sides and ESHB muscles were chilled at 5–7°C until 24 hr postmortem; then 2–4°C for 24 hr. At 48 hr postmortem, steaks were cut, vacuum packaged and aged (2–4°C) for 4 days. Beef flavor was more intense for control steaks than for steaks from either ESHB chilling treatment. No other differences were noted.     

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.     

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.     

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments. PRACTICAL APPLICATION: Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.     

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 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.     

Effect of Electrical Stimulation and Steak Temperature at the Beginning of Cooking on Meat Tenderness and Cooking Loss

Six steaks from each of 24 loins (from electrically stimulated and control sides of each of 12 steers) were thawed to produce steak temperatures of 2, 7,13,14,18 or 26°C just prior to cooking. After cooking to 70°C steaks with a starting temperature of 26°C were 30% more tender than those with a starting temperature of 2°C. Electrical stimulation increased tenderness of steaks from all treatments (an average of 23%), and no interaction was found between electrical stimulation and starting steak temperature. Tenderness and cooking loss can be optimized by electrically stimulating carcasses and by starting cookery when steaks have high internal temperatures.     

Biochemical and Quality Characteristics of Ovine Muscles as Affected by Electrical Stimulation, Hot Boning, and Mode of Chilling

The combined effects of electrical stimulation and carcass holding temperature were evaluated on some biochemical and quality characteristics of intact and hot-boned ovine muscles. Twenty-four lamb sides were randomly assigned to four treatments. Electrical stimulation was performed within 15 min postmortem (350 V with 10 Hz) for 4 min. Electrically stimulated and slowly chilled (5 hr at 14 ± 2°C) sides significantly exhibited more rapid pH decline in the longissimus dorsi (LD) muscle, less cold shortening in the semitendinosus (ST) muscle and greater tenderness in both LD and ST muscles than sides chilled at 2°C. None of the treatments had any effect on cooking loss in ST and LD muscles, lean color of LD muscle during a 4-day retail display, and solubility of different protein fractions as well as the swelling factor of the stroma protein of LD muscles.     

Effects of Time Postmortem of Electrical Stimulation and Postmortem Chilling Method on Pork Quality and Palatability Traits

Twenty market hogs were used in this study to determine the effects of electrical stimulation (ES) administered at various times postmortem (5, 15-20, or 30-40 min) and chilling treatment (Conventional = 24 hr at 0-2°C, or Rapid = 34°C for 3 hr then 0-2°C for 21 hr) on pork quality and palatability traits. The findings of this study indicated that ES of hog carcasses, particularly at 5 or 15-20 min postmortem, detrimentally affects quality by inducing a paler color, reducing muscle firmness, and increasing muscle separation. Rapid chilling lessened these detrimental effects. Cooking loss, cooking time. shear force values, and palatability traits were not affected by ES or chilling rate.     

Physical-Chemical Properties and Cooking Yield of Hamburgers Prepared from Accelerated Processed Beef

The effect of time of processing, pre- vs post-rigor, on quality of hamburgers prepared from electrically stimulated beef was investigated. Within 2 hr postmortem flanks of right sides of 8 electrically stimulated (85 V, 14 Hz, 30 s) and 8 nonstimulated cow carcasses were hot-processed into hamburgers. Flanks of left sides were cold-processed after 20 hr at 1 ± 1°C. Electrical stimulation resulted in significantly higher cooking losses than no stimulation. Hot processed hamburgers from nonstimulated beef had lowest cooking losses whilst hot-processing virtually nullified adverse effects of stimulation on cooking yield. Irrespective of electrical stimulation, shear forces for hot-processed hamburgers were lower than shear forces for cold processed hamburgers. Increased brightness (higher L*-values) observed in hot-processed hamburgers was a result of fat-smearing.     

The electrical stimulation of beef carcasses

Beef carcasses were stimulated shortly after slaughter at varying voltage, pulse frequency and duration, with the aim of accelerating the fall of pH, destruction of ATP and onset of rigor in the muscles, so that the meat could be chilled rapidly after slaughter without danger of cold-shortening. Optimal effects were produced at 700 V, 25 Hz for 2 min, to give a total of 3000 pulses. In undressed carcasses stimulation induced a pH fall to 6.0 within 1 h of slaughter and to 5.7 within 2.5 h in the major muscles of the forelimb, back and thigh, representing a gain of more than 8 h over the time required in unstimulated carcasses hanging at 16°C. Similar results were obtained with dressed carcasses and sides, after allowing for the 50 min or so lost in dressing. The apparently high rate of pH fall from 6.3 to 5.7 after stimulation had ceased, compared with that over the same pH range in unstimulated carcasses, can be attributed mainly to the different muscle temperatures in the two cases (38 and 26°C respectively, in four major muscles). The muscles of stimulated carcasses showed no deleterious effects of stimulation. The observed drip loss from the hindlimb jointed 6 days after slaughter was not significantly greater than that from unstimulated carcasses.     

THE SHEAR FORCE OF VERY-RAPIDLY CHILLED LAMB 1: THE EFFECT OF CARCASS SPLITTING

The effect on tenderness of splitting lamb carcasses longitudinally under very-rapid chilling conditions was investigated. Whole (unsplit) and split carcasses were chilled in very-rapid chilling conditions (−20C for 3.5 h followed by chilling at 4C for 20.5 h) and conventional chilling conditions (4C for 24 h), giving a total of four treatments. Loin (M. longissimus thoracis et lumborum) shear force was measured at f and S days postmortem by Warner-Bratiler shear force measurement. By 5 days postmortem, split carcasses were not different (P>0.05) in shear force to unsplit carcasses when conventionally chilled but differences (P<0.05) were present between unsplit and split carcasses when very-rapidly chilled (57.7 N vs 41.5 N, respectively).     

Effects of Electrical Stimulation and Hot-Boning on Physical Changes, Cooking Time and Losses, and Tenderness of Beet Roasts

Beef semimembranosus and semitendinosus muscles were removed prerigor (1 hr postmortem) and postrigor (7 days postmortem) after one-half of the left and right sides were electrically stimulated. The influence of electrical stimulation and hot-boning upon physical changes; cooking losses; shear force; taste panel evaluation; and time required to heat product to an internal temperature of 63°C was studied. There was no consistent influence of electrical stimulation upon physical changes of prerigor muscles or upon tenderness of pre– or postrigor roasts. Hot-boned and precooked roasts were less tender than cold-boned counterparts. Cooking yields were not altered by electrical stimulation. Prerigor roasts had 9% higher yields than postrigor roasts. Prerigor roasts from electrically stimulated sides required a longer time to cook to 63°C than roasts from the control sides. Hot-boning reduced the length of time of cooking (95 min/kg to 72 mm/kg of raw weight).     

ULTRA-RAPID CHILLING: CHILLING RATE EFFECTS ON THE APPEARANCE OF LAMB CARCASSES AND TENDERNESS OF LAMB CHOPS

The effects of different chilling rates on the visual attributes of lamb carcasses and the tenderness of lamb chops were investigated. Carcasses (n=72) were chilled at -20C, -10C, -4C or + 4C. After chilling all carcasses were stored at +4C for up to 8 days. Samples were taken at 2, 6 and 9 days postmortem for sarcomere length, Warner-Bratzler shear force and sensory analysis. Carcasses were visually appraised at 2, 6 and 9 days postmortem for fat color, flank color, visible vein color, wetness and overall acceptability. Carcasses chilled at -20C had significantly higher Warner-Bratzler shear force values than the other chilling treatments at 2 and 6 days but not at 9 days postmortem. No difference (P> 0.05) was found in Warner-Bratzler shear force or sensory tenderness between any of the treatments by 9 days postmortem. Carcasses did not differ (P>0.05) in fat color, flank color or overall acceptability at any stage postmortem. Carcasses chilled at -20C had slightly darker (P< 0.05) vein color at 2 days postmortem but this was not evident by 6 days postmortem. Carcasses that were chilled at -20C had significantly lower evaporative weight losses than carcasses in any of the other treatments. Rapid chilling did not adversely affect the tenderness of lamb chops or appearance of lamb carcasses at 9 days postmortem compared with conventional chilling.     

Effect of chilling applied to suckling lamb carcasses on hygienic,physicochemical and sensory meat quality

The effect of post mortem temperature treatment on suckling lamb carcass and meat quality was study. Conventional (2 °C for 24 h), ultra-rapid (− 20 °C for 3.5 h, 2 °C until 24 h) and slow chillings (12 °C for 7 h, 2 °C until 24 h) were compared. Total viable counts (TVC), weight losses, and pH and temperature falls were recorded on carcasses. Meat colour, water holding capacity (WHC), Warner-Bratzler shear force, sarcomere length and sensory analysis were evaluated in M. longissimus. Ultra-rapid treatment reduced TVC and weight losses. The pH decline was faster in slow chilled carcasses than in faster chilled carcasses. No significant differences were found for colour and WHC. Slow treatment carcasses showed significantly lower shear force and higher sarcomere length. In the sensory analysis, tasters also rated the early post mortem slow-treated meat as more tender, less fibrous and chewy. Therefore, delay chilling in suckling lamb carcasses made it possible to obtain meat with better organoleptic characteristics, without affecting weight loss or hygienic quality.     

Investigation of methods to detect mechanically recovered meat in meat products - III: Microscopy

Carcasses from 36 Large White gilts, 70–80 kg live weight, were randomly allocated to three experimental groups. Pigs in the first group were electrically stimulated with low voltage during bleeding (85v, 14Hz for 64 s) and split before cooling. The left sides were rapidly chilled in air at -15°C for 75 min and then at 1°C until 24 h post-slaughter; right sides were chilled conventionally in air at 1°C for 24 h. In the second group, two different treatments were used 20 min post-slaughter: left sides were stimulated with low voltage, and right sides with high voltage (700 v, 12·5 Hz for 90 s). Both sets of sides were chilled rapidly. Carcasses from the third group were not stimulated, and sides chilled either rapidly or conventionally. Drip loss, colour and texture were measured in M. longissimus thoracis et lumborum at 3 and 10 days post-slaughter.

At 3 days post-slaughter the high voltage, treatment gave meat which was the most tender, was not pale and lost no more drip than unstimulated controls. Low voltage stimulation during bleeding gave meat which was 18% more tender than the unstimulated controls, but the improvement in tenderness was not as great as the 28% achieved with high voltage. Unexpectedly, low voltage stimulation applied 20 min after slaughter, was almost as effective in improving tenderness (by 17%) as low voltage applied during bleeding.

Tenderness improved from 3 days to 10 days in all stimulated samples, but not in unstimulated controls. The results suggest a degree of coldtoughening in the latter, even with conventional chilling, and a positive effect of electrical stimulation on tenderness, independent of its protective action against cold-shortening.     

Oxidative Stability and Sensory Attributes of Prerigor Cooked Beef Steak

Beef sirloin tip steaks from 12 steer carcasses were cooked prerigor and postrigor using three heating methods and stored at 4 °C or ‐20 °C. Prerigor cooked steak had lower cook loss, higher pH, higher shear force, and sensory hardness than postrigor cooked steak. Conventional oven cooking produced the lowest cook loss for prerigor steak. Prerigor cooked steak had lower thiobarbituric acid value than postrigor cooked samples after 2 wks at 4 °C or 3 mo at ‐20 °C. Sensory warmed‐over flavor intensity scores were low and showed no differences between prerigor and postrigor cooked steaks for refrigerated or frozen samples.     

Effects of Electrical Stimulation, Boning Time and Cooking Method on Beef Roasts

Sixteen steer carcasses were selected to study effects of electrical stimulation, boning time and cooking methods on palatability traits, cooking loss and chemical composition of beef biceps femoris muscle. Eight carcasses were electrically stimulated and eight carcasses served as controls. The biceps femoris muscle was removed from one side of each carcass within 2 hr of exsanguination and from the remaining side following a 48-hr chill. Muscles were subdivided and cooked in either a convectional electric or a microwave oven. Electrical stimulation resulted in longer (P < 0.01) sarcomeres for cooked product but did not affect palatability traits, cooking loss or chemical content. Hot boning reduced (P < 0.01) cooking loss and tenderness, resulted in less (P < 0.05) total, soluble and insoluble collagen and increased the juiciness score and moisture percentage when compared with 48-hr boning. Microwave cooking produced a greater (P < 0.01) cooking loss and a higher shear force value than convectional electric cooking.     

Influence of Electrical Stimulation, Cooling Rates and Aging on the Shear Force Values of Chilled Lamb

An investigation using high voltage (800 VRMS, 1140 V peak at 14.3 Hz) electrical stimulation (ES) showed that lambs should be stimulated within 30 min of slaughter for 60–120 sec for maximum effect on Warner-Bratzler shear force values. Shear force values of lamb muscles chilled at different rates were significantly (P<0.001) reduced by ES, compared with nonstimulated controls. However, aging at temperatures between 0° and 9°C, for only 2–3 days, educed shear force values of nonstimulated lamb subjected to moderate chilling rates to those of ES samples at 1 day postmortem. Increasing aging temperature significantly (P<0.001) increased aging rate but duration of aging had the greater effect.     

Influence of Hot and Cold Boning on the Palatability, Textural and Economic Traits of Restructured Beef Steaks

Steaks containing 0.01% BHA, 0.75% NaCl and 10% fat were fabricated from hot- and cold-boned sides of four U.S. Standard, seven U.S. Good and one U.S. Choice steer carcasses. Carcasses were electrically stimulated (550 volts, 2.2 amps) ca 37 min postmortem. One side from each carcass was boned 4 hr postmortem (HB) while the other was placed in a 5°C cooler and boned 96 hr postmortem (CB). Hot boned sides required 29% less time to bone and yielded more (P<0.01) restructurable meat, less (P<0.05) lean trim and a heavier boneless loin. Cold-boned steaks had higher (P<0.05) bonding strength than hot boned steaks. No differences were found in juiciness, tenderness, flavor desirability, amount of connective tissue or cooking loss due to boning time. Restructured steaks produced from HB sides had a lower breakeven cost than steaks from the CB side. This was attributed to the higher yield of restructurable meat and more expedient boning.