Effect of 3 postmortem electrical stimulation treatments on the quality of early deboned broiler breast meat

The present experiment was carried out to evaluate the effects of electrical stimulation (ES) immediately prescalding (PS), ES immediately postdefeathering (PD), or PS combined with PD (PSPD) on the quality of early deboned (2 h) broiler breast muscles, pectoralis major (fillets), and pectoralis minor (tenders). No stimulation, early-deboned (2 h), and 24-h deboned (24 h) fillets were used for the comparison. The 42-d-old broiler carcasses were electrically stimulated with pulsed current at 200 V for 30 s over a 90-s time interval (total of 1 min over 180 s for PSPD), and breast meat was deboned 2 h postmortem. Quality indicators evaluated were CIE L*, a*, and b* color and pH of the raw fillets and cook yields and Warner-Bratzler (WB) shear force of the fillets and tenders. There were no differences in raw fillet color, pH, and cook yields of both the fillets and tenders between the 3 ES treatments. Effects of different ES treatments on meat WB shear force values varied with breast muscles. For the fillets, the average WB shear force values of both the PS and PSPD samples, which were not different from each other, were significantly lower than those of the PD samples. For the tenders, there were no differences in the average shear force values between the 3 ES treatments. Regardless of ES treatment and breast muscle, early deboned broiler breast meat from ES carcasses required significantly less force to shear than the 2-h control. These results indicate that ES can tenderize early deboned poultry breast muscles; however, the effectiveness of ES tenderization varies with ES treatments for the fillets. The PS treatment is more effective in reducing fillet shear values than PD, and there is no further reduction in shear values with PSPD compared with the PS treatment.

Research note: Functionality of electrically stimulated broiler breast meat

Postmortem electrical stimulation (ES) tenderizes meat by acceleration of adenosine triphosphate (ATP) depletion, pH decline, and physical disruption of muscle fibers. It has been demonstrated that rigor development at elevated temperatures, as with slow chilling, can cause meat to develop pale color and poor water-holding capacity. The objective of this study was to compare the functionality of broiler breast meat from control and electrically stimulated carcasses with and without normal rapid chilling. Broilers were either electrically stimulated (450 mA, 450 V, 2 s on, 2 s off for 7 pulses) immediately after bleeding or used as nonstimulated controls. The ES birds were either chilled immediately (ES2) or had chilling delayed for 2 h at room temperature (ESD2). All ES breast fillets were harvested at 2 h postmortem. The control carcasses were chilled immediately and had fillets harvested at 2 h postmortem (C2) or at 8 h postmortem (C8). Electrical stimulation accelerated pH decline and prevented toughening when breast meat was deboned at 2 h postmortem, regardless of chilling rate. The water released from the gels during cooking was higher for the ESD2 than the ES2 group, which was not different from the C2 group, suggesting that ES followed by slow chilling reduced water-holding capacity compared with the ES2 and C2 groups. There were no differences in expressible moisture, gel strength, or lightness among the ES2, ESD2, and C2 treatments. These results indicated that high voltage ES followed by normal chilling did not impair protein functionality or cause pale, soft, exudative meat. However, there was some evidence that slow chilling after ES may negatively affect some water-holding properties of the meat.

Effects of stunning and decapitation on broiler activity during bleeding, blood loss, carcass, and breast meat quality

Four experiments were conducted to determine the effects of electrical stunning and decapitation on bird activity as well as carcass and meat quality. In Experiment 1, broilers were subjected to one of four stunning and killing methods: no stun and neck cut, stun and neck cut, no stun and decapitation, and stun and decapitation. Birds were scored for severity of physical activity on a scale of 1 to 4 with 1 being no activity and 4 being severe wing flapping and muscular contractions. Carcasses were also scored for red wing tips and broken bones. In Experiments 2 to 4, all birds were stunned prior to neck cut or decapitation. Carcasses were scored as described in Experiment 1 as well as measurements of blood loss, feather removal, and breast meat pH, color, cook loss, and tenderness. Based on carcass activity in Experiment 1, decapitation following stunning was similar to a conventional stun and unilateral neck cut, except there was almost no late activity (after 60 s) observed in the decapitated birds. Decapitation following stunning did not result in any consistent carcass quality defects compared to conventional killing in the four experiments. No differences were found in 24-h lightness values, yellowness, cook yield, tenderness, and ultimate pH between conventionally killed and decapitated birds. Blood loss and breast meat redness were inconsistent. These results indicate that high frequency stunning and decapitation may be an acceptable alternative to conventional slaughter based on carcass and meat quality and by ensuring an irreversible loss of consciousness.

Effect of some electrical stimulation variables on wing flapping, post-mortem glycolysis and eating quality characteristics of broiler pectoralis major muscle

1. The influence of different rates of wing flapping on the rate of post-mortem glycolysis in the Pectoralis major (PMI) muscles of commercially-processed broilers was investigated. This was achieved by applying 300 pulses of low voltage electrical stimulation (ES) shortly after slaughter at various frequencies and pulse widths. The rate of post-mortem glycolysis was assessed by measuring muscle pH values at 20 min post mortem (pH(20 min)). 2. ES gave a mean pH(20 min) value of 6.01, significantly lower than that of the control carcases which had a mean value of 6.45. Within ES treatments, variation in pulse frequency between 1/s and 10/s and in pulse width from 5 to 20 ms had no influence on pH(20 min) values as measured by direct probe. However, differences between mean pH(20 min) values attributable to pulse frequency were detected when measured by the iodoacetate method. 3. A further experiment was carried out to determine how different rates of wing flapping would affect the eating quality of PM muscles from commercially-processed broilers stored at chill temperatures for 24 h post mortem. This was achieved by using pulse frequencies of 1/s, 5/s and 10/s, all other ES variables being standardised. Pulse frequency had no effect on ultimate pH, sarcomere length, cooking loss or tenderness of PM muscle compared to controls. 4. We concluded that the rate of wing flapping post-slaughter has no effect, per se, on the extent of post-mortem glycolysis in broiler PM muscle or on its subsequent meat quality assessed after holding the carcases under chill storage conditions for 24 h.

Quality and sensory characteristics of selected post-rigor, early deboned broiler breast meat tenderized using hydrodynamic shock waves

Our first objective was to determine the effects of explosive amount and distance of the explosive to the meat surface in the Hydrodyne process on broiler breast tenderness. Early deboned (EB) breasts were removed immediately after initial chill (45 min postmortem), stored for 24 h (4 C), and subjected to one of four Hydrodyne treatments (200 g at 20 cm, 350 g at 23 cm, 275 g at 20 cm, or 350 g at 20 cm). Breasts were water-cooked (78 C internal). Hydrodyne treatment (HYD) of 350 g at 20 cm produced the greatest reduction (28.3%) in Warner-Bratzler shear (WBS, 1.9-cm wide strips). This combination was the only treatment to improve tenderness (peak force 4.3 kg) to a level equivalent (P > 0.05) to aged controls (CA; peak force 3.1 kg). The second objective was to determine the quality and sensory characteristics of Hydrodyne-treated (350 g explosive at 20 cm) broiler breasts as compared with CA and EB. The WBS values (1.0-cm wide and thick strips) for CA (1.56 kg) were different from both HYD (3.7 kg) and EB breasts (4.7 kg). The CA resulted in more tender, flavorful, and juicer breasts than EB and HYD. The EB was higher in initial moisture release than HYD. The EB breasts with tenderness problems can be tenderized by the Hydrodyne process based on WBS results. However, higher levels of explosive may be required to optimize the tenderness improvement of EB breasts that vary significantly in initial tenderness.

Meat quality during processing

The study of growth and development of any food animal such as poultry needs to consider the effects of the muscle changes on the use of the muscle as meat. If a treatment could increase muscle growth but the increased meat was of poor quality, then the increase in production would be of little value. Muscle is of particular concern because not only is it the tissue of greatest value for food, but it also is an excitable tissue and responsive to its environment. Many of these responses can be quite deleterious to meat quality. The basis for the response of muscle to its environment is in postmortem metabolism and the simultaneous development of rigor mortis. Although the animal may die in a matter of minutes following the neck cut, its muscle cells continue to metabolize and respond for hours after respiratory cessation and brain death. During these hours, the muscle has energy that fuels the responses to the environment, most commonly in terms of color and texture. Heat, transportation, and handling all contribute to the preslaughter stress that can alter color, texture, and related protein functionality. Stunning is another preslaughter factor that has a large effect on postmortem metabolism and meat quality. After death, chilling can toughen meat while it adds juiciness, and aging prevents the meat from toughening in response to deboning. Electrical stimulation is a recent beneficial innovation that reduces the need for aging by accelerating postmortem energy depletion and reducing the muscle's ability to toughen during deboning. This paper reviews the responsiveness of the muscle and gives examples of how these responses can hurt or help meat quality.

The effects of antemortem electrical stunning and postmortem electrical stimulation on biochemical and textural properties of broiler breast meat

Experiments were conducted to determine the combined effects of antemortem electrical stunning (STUN) and postmortem electrical stimulation (STIM) on breast muscle rigor development and meat quality attributes. Birds were either unstunned, stunned with low voltage (LV), or stunned with high current (HC) prior to conventional killing. Immediately after exsanguination, birds were either unstimulated, or were subjected to electrical stimulation with 12 1s on/1s off pulses of 440 V AC and allowed to bleed for 90 s to determine the effect of treatment on blood loss. Breast fillets (Pectoralis major) were removed from carcasses immediately after evisceration (0.25 h) or after aging in a static ice-water slush for 1 or 2 h, and analyzed for muscle pH, R-value (ratio of inosine to adenosine nucleotides), and sarcomere length. Raw breast meat color (CIELAB), cook loss, and shear values were determined on samples held at 2 C for 24 h. Results showed both STUN and STIM significantly affected blood loss, pH, R-value, sarcomere length, color, and shear, and there were significant STUN by STIM interactions. Blood loss was significantly lower for the HC STUN and all the STIM treatments. STIM at 440 V resulted in accelerated rigor development as measured by pH, R-value, and sarcomere length, similar to the unstunned or LV STUN samples, but different from the HC STUN birds. These results indicate that electrical stimulation may accelerate rigor most effectively following high current stunning, which tends to delay early rigor development.

Commercial implementation of postmortem electrical stimulation

Postmortem electrical stimulation (ES) of meat-producing species is not a new technology but has recently been adapted for commercial use with poultry. Unlike its use in red meats to reduce the inherent toughness and facilitate grading, the application of ES in poultry is to reduce the need for aging carcasses before deboning by reducing the toughening that occurs when the meat is deboned early after death. The current practice of aging intact carcasses or breast halves 4 h or more prior to deboning costs the industry millions of dollars in lost yield and creates logistical problems in plants. Electrical stimulation reduces the need for aging by accelerating the energy depletion involved in rigor mortis development to reduce the shortening-related toughness of early deboning. Some ES systems have the additional effect of inducing physical disruption in the muscle, reducing muscle integrity and counteracting the toughness induced by early deboning. Several ES systems have been reported in the literature with some having been recently developed into commercial-scale devices. With this new technology and the growing pressure on processors to maximize operating efficiencies, processors will need to evaluate their tenderness management programs and customer demands to determine the role ES can play in their operations.

Meat quality of broiler breast meat following post-mortem electrical stimulation at the neck

This experiment was conducted to evaluate the effects of electrical stimulation (ES) on breast fillets harvested at 1 h post-mortem and individually quick frozen (IQF) or aged on ice (ICE). Twelve birds were electrically stimulated (450 V, 750 mA, 2 s on/1 s off for 15 s) at the neck in a saline bath. Twenty-four unstimulated birds were used as controls. Breast fillets were harvested at 1 h post-mortem from ES and control carcasses or at 4 h post-mortem from control carcasses and were either IQF or ICE until 24 h post-mortem. Fillets were then analyzed for shear value, pH, R value, and color. Electrical stimulation significantly reduced shear values compared to the 1 h controls for both IQF and ICE treatments. The ICE fillets deboned at 1 h from ES-treated carcasses had shear values similar to those of ICE fillets deboned from the 4 h controls. Electrical stimulation increased the percentage of shear values at or below 8 kg/g for the fillets from ES-treated carcasses compared to the 1 h controls. Electrical stimulation accelerated the normal post-mortem decline in pH and increase in R value. There was no significant difference in L* or a* values between the fillets held for 1 or 24 h. The results suggest that by electrically stimulating carcasses at the neck using a saline bath, the aging period could be eliminated by removing fillets immediately after chilling at 1 h, decreasing the costs associated with aging whole carcasses or front halves.

Effect of electrical stimulation in combination with calcium chloride or sodium chloride treatments at constant ionic strength on moisture binding and textural quality of early-harvested breast fillets

The objective of this study was to assess the effects of a CaCl2 or NaCl treatment combined with electrical stimulation (ES) on textural and moisture binding of early-harvested chicken breast fillets. During exsanguination, half the birds were subjected to ES, and then all carcasses were aged for 30, 60, 90, or 120 min before excising both Pectoralis major muscles. Half the muscles were chilled with a NaCl solution and half with a CaCl2 solution. Effects of ES and chill medium composition on meat pH, moisture absorption, cooking loss, and shear value of the fillets were assessed. The ES reduced meat pH for the NaCl-treated muscles, but had no effect on those treated with CaCl2 of on moisture absorbed during chilling. Cooking loss was greater for the CaCl2-treated than NaCl-treated muscles and for muscles from stimulated birds that were excised more than 30 min post-mortem. Shear values were unaffected by chilling medium composition. However, even though shear values for both ES and unstimulated birds declined as aging time increased, the rate of decline was greater, and ultimate shear value lower, for muscles from ES birds. Results indicate that, although ES might offer some advantage in improving the tenderness of early-harvested breast fillets, combining ES with CaCl2 treatment offers no real advantage. Moreover, reductions in moisture binding properties by these technologies might limit applicability in some commercial environments.

Muscle metabolism and meat quality of Pectoralis from turkeys treated with postmortem electrical stimulation

This experiment was conducted to evaluate the effects of electrical stimulation (ES) on muscle metabolism and breast meat quality in turkeys. Thirty-six turkey hens were either ES at the neck in a saline bath (570 V, 450 mA, AC, 60 Hz, 2 s on 1 s off for 10 pulses) or used as unstimulated controls. One breast fillet from all carcasses was harvested at 2 h postmortem. The opposite fillet was harvested from the ES carcasses at 8 h postmortem and from the unstimulated controls at either 8 or 24 h postmortem. All fillets were sampled at time of deboning for expressible moisture, pH, R-value, gravimetric fragmentation index (GFI), and sarcomere length. The remainder of the fillet and the samples for GFI and sarcomere length were aged on ice until 24 h postmortem. After aging, fillets were analyzed for cook loss and shear value. Color was measured at time of deboning and at 24 h postmortem. Electrical stimulation accelerated rigor mortis development as indicated by significantly lower pH values and higher R-values at 2 h postmortem when compared to control fillets. The pH and R-values of the 2-h ES treatment were not significantly different from the 8-h ES, 8-h controls, or the 24-h controls. Fillets from carcasses that were ES and deboned at 2 h had significantly longer sarcomeres than the 2-h controls; however, there were no significant differences between the 2-h ES and the 8-h ES treatments, 8-h controls, or the 24-h controls. Although ES accelerated muscle metabolism at 2 h postmortem, it had no effect on shear value, expressible moisture, cook loss, GFI, L*, or a* color values. These results suggest that this postmortem ES system would not benefit turkey processors.

The effects of post-mortem electrical stimulation and muscle tensioning in two broiler muscles

High voltage post-mortem electrical stimulation (ES) and muscle tensioning during chilling (MT) were applied to broiler carcasses to determine the effect of this combined treatment on absorbance ratio (R- value), sarcomere shortening, and myofibrillar fragmentation in muscles of differing fiber type composition. The ES + MT treatment resulted in a greater effect on these three parameters in the posterior Latissimus dorsi (predominantly twitch-glycolytic) than in the anterior L. dorsi (predominantly tonic-oxidative). The differing responses of these two muscles to the ES + MT treatment combination may be useful in explaining the effects of rigor-accelerating treatments such as ES + MT in avian and mammalian muscles.