The impact of new generation pre-dressing medium-voltage electrical stimulation on tenderness and colour stability in lamb meat

Electrical stimulation and wet ageing effects on the carcass and meat quality of Australian rangeland goats

Medium voltage electrical stimulation and wet ageing periods effects on the carcasses and meat quality of Australian rangeland goats were investigated. 64 rangeland goats were slaughtered as 2 equal consignments, wherein half were exposed to post-dressing electrical stimulation (300 V, 500 ms pulse width, 45 s) and half were not (control). Carcass and pH decline parameters and glycogen concentration were recorded. At 24 h post-mortem, fresh colour was measured and longissimus lumborum muscles (LL) removed. Within carcass, paired LL were halved and allocated to each of 4 ageing periods (1, 2, 4, or 21 d). There were no significant effects from electric stimulation on LL pH at 18 °C, LL temperature at pH 6, LL pH at 24 h post-mortem, semitendinosus pH at 24 h post-mortem, and LL glycogen concentration. There were no significant interactions between stimulation and ageing period on cooking loss, particle size, purge loss, sarcomere length, shear force, and ultimate pH. Independent to stimulation, shear force, particle size, and cooking values declined as ageing period increased. Purge loss was highest after 21 d of ageing. Colour stability was unaffected by ageing, although all CIE colour coordinates varied across the 74 h total retail display period. There were negative linear relationships found between LL glycogen concentrations and LL temperature at pH 6, ultimate pH, and sarcomere length. These findings suggest there to be little benefit to post-dressing electrical stimulation of rangeland goat carcasses, when applied independent to or in combination with ageing.

Effects of medium voltage electrical stimulation on initial pH decline and quality parameters during ageing and frozen storage of Nellore beef

This study aimed to evaluate the influence of medium voltage electrical stimulation (ES) at three different intensities, 200 V (Treatment 200 V, T200), 300 V (Treatment 200 V, T300), and 400 V (Treatment 400 V, T400) on the initial pH decline in post mortem muscle and the quality parameters on M. longissimus thoracis - Nellore beef, both throughout the ageing process and during frozen storage. The colour, cooking loss, and shear force parameters for samples of aged beef were determined. Additional parameters, like thaw loss, pH, and lipid oxidation were also analyzed for the frozen storage. The shear force and cooking loss decreased and colour parameters increased in Nellore beef ES compared with CON on ageing time (14 days). At frozen storage, quality parameters like pH, a*, and b* were reduced over time, and no negative effect on lipid oxidation was found. Electrical stimulation at 200 V demonstrated effectiveness for decreasing shear force to Nellore beef (M. longissimus thoracis) during frozen storage. The application of medium voltage electrical stimulation can contribute to improved quality and tenderness in Nellore beef, both during ageing and frozen storage conditions.

A Comparison of Two Different Slaughter Systems for Lambs. Effects on Carcass Characteristics, Technological Meat Quality and Sensory Attributes

Simple Summary

Slaughter systems for lambs can differ in many ways, as they are optimised to meet site-specific conditions, and may affect carcasses differently. It is therefore important to assess whether different slaughter systems affect meat quality parameters such as colour and tenderness, which are important meat quality factors from a consumer perspective when buying a meat product. This study investigated whether two slaughter systems differing in stunning method, electrical stimulation of carcasses and chilling regime resulted in differences in quality attributes in meat from intact male lambs. It also examined whether breeding for carcasses with a higher incidence of lean muscle and less fat content has affected tenderness scores for Icelandic lambs over time. The results showed that the two slaughter systems tested did not affect meat quality parameters to any large extent. Further analysis showed an increase in mechanical tenderness values in meat samples from the Icelandic lamb population over time, which could be due to selective breeding for carcasses with higher muscle and less fat content.

Abstract

Two slaughter systems for lambs and their effects on meat quality in terms of texture, colour and sensory attributes were compared. The slaughter systems differed in methods for controlling rigor mortis and carcass chilling. One slaughter system (large-scale) used electrical stimulation and fast chilling of carcasses, while the other system (small-scale) did not use electrical stimulation and applied slower chilling, with carcass temperature decreasing over a longer period after slaughter. Ten pairs of ram lamb twins were selected, and one of each pair was slaughtered at the large-scale abattoir and the other at the small-scale abattoir. Carcass weight, conformation, fatness, pH and temperature were recorded. Musculus longissimus thoracis et lumborum was analysed for colour, cooking loss, Warner–Bratzler shear force and sensory attributes. For meat quality attributes, the only differences were found in meat colour L* (lightness; p = 0.0073), sensory attribute “appearance colour” (p = 0.0089) and “fatty flavour” (p = 0.0554). Meat from the small-scale abattoir was darker in colour and had a more fatty flavour than the meat from the large-scale abattoir. For sensory attributes (apart from colour), no significant differences were found between the two abattoir systems.

The quality and mineral composition of the longissimus lumborum and semimembranosus muscles from lambs fed perennial or annual wheat forage with or without lucerne

This study compared the effect of a novel perennial wheat forage and a conventional annual wheat forage, fed to lambs with or without lucerne, on the quality and mineral profile of the longissimus lumborum and semimembranosus muscles. This involved 48 Poll Dorset × Merino ewe lambs, 12 per treatment, managed for 28 days within individual pens. Consumer sensory panel scores showed 'good eating quality' for all samples irrespective of diet, a conclusion supported by the shear force, cooking loss, particle size, and intramuscular fat results. Drip loss was affected by a significant interaction between diet and muscle. The ultimate pH of meat from lambs fed annual wheat was highest. Comparable colour stability and purge results suggested that diet did not impact on lamb retail-potential. Sodium, sulphur and zinc concentrations were higher in the meat from lambs fed annual wheat, compared to perennial wheat. Overall, these outcomes support the use of perennial wheat as a forage for lamb production.

Color Attributes and Glycolytic Energy Metabolites of Meat From Light and Heavy Bovine Feedlot Carcasses Stimulated With Low-Voltage Electricity

This study investigates the influence of timing and duration of low-voltage electrical stimulation (ES) as well as carcass weight, which are important factors affecting muscle glycolysis and meat color attributes. Longissimus samples from 147 cattle, representative of typical South African feedlot cattle, were assigned to 10 treatment groups according to the combination of carcass weight (small or heavy), time of ES (early [7 min] or late [45 min] postmortem), and duration of ES (30 or 60 s). Early ES and longer ES duration (60 s) produced the highest (P < 0.05) meat lightness (L*). The combination of early ES and heavier carcasses produced the highest (P < 0.05) chroma (C*) 2 d postmortem (butchery period). These results were corroborated by the energy metabolites, such that early stimulation produced the highest amount (P < 0.05) of muscle lactate, glucose, and glucose-6-phosphate, as well as the lowest glycogen, creatine phosphate, and adenosine triphosphate early postmortem. This shows that the application of low-voltage ES on heavier carcass is advantageous in terms of meat color, but the advantages diminish as ageing progressed from 2 to 14 d postmortem.

Effect of Carcass Electrical Stimulation and Suspension Methods on Meat Quality Characteristics of Longissimus lumborum of Young Buffalo (Bubalus bubalis) Bulls

Buffalo animals are slaughtered at their early age and carcasses are chilled rapidly which deteriorates its meat quality and decreases the consumer likeliness of buffalo meat. This study investigated the appropriate methods to prevent the quality deterioration of buffalo meat during chilling. Twenty four 18-mon-old buffalo bulls were slaughtered, electrically stimulated and suspended either by hip or achilles tendon. After 24 h postmortem, meat quality characteristics were recorded. Results showed that electrical stimulation (ES) led to rapid decline of carcass pH compared to non-ES method (p<0.05). Furthermore, electrically stimulated meat presented lower shear force accompanied with the higher CIE L*, a*, and b* values (p<0.05). Suspension methods only affect the meat shear values and were lowered in hip suspended samples. It can be concluded that ES combined with hip suspension can be adopted to prevent the meat quality deterioration of young buffalo bulls during postmortem storage.

A Meta-Analysis of the Effectiveness of High, Medium, and Low Voltage Electrical Stimulation on the Meat Quality of Small Ruminants

The current study is a meta-analysis of the effects of electrical stimulation (ES, n = 28 papers) with different voltages combined with different ageing periods (0–3, 4–7, and 8–14 days) on the meat quality of small ruminants. A comprehensive search for published studies on meat quality of small ruminants investigating the application of low, medium, and high voltage electrical stimulation, was performed using Google Scholar, ScienceDirect, PubMed, and Scopus databases. Forest plots, funnel plots, and other statistical tools and tests were used in the study to analyze the results. Electrical stimulation significantly reduced ultimate pH (p < 0.001), Warner–Bratzler shear force (WBSF) (p < 0.001), cooking loss (p < 0.05), and purge loss (p < 0.001). In addition, sarcomere length (p < 0.01), myofibrillar-fragmentation index (MFI) (p < 0.001), and color (L*, a*, b*) (p < 0.001) showed higher values in meat subjected to ES as compared with the control group. In conclusion, the meta-analysis revealed statistical proof of beneficial effects of ES on meat quality of small ruminants in terms of ultimate pH, tenderness, enhanced proteolysis, and higher colorimetric values.

Effect of medium voltage electrical stimulation and prior ageing on beef shear force during superchilled storage

The effect of medium voltage electrical stimulation (ES), prior ageing (0-4 °C, 7 days), and their combination on the decrease of shear force in beef during superchilled storage (-4 °C) for 24 weeks was evaluated, in the context of a high shear force obtained under this storage condition. Both ES and prior ageing significantly reduced the initial Warner-Bratzler shear force, and the combination of ES and prior ageing shortened the storage time needed to reach an acceptable shear force of superchilled beef, which is mainly due to increased myofibrillar degradation as indicated by changes in desmin (P < 0.01, r = 0.35). Additionally, ES and prior ageing did not negatively affect lipid oxidation, total volatile basic nitrogen or water loss of superchilled beef. Consequently, ES combined with ageing for 7 days offered an effective approach for decreasing shear force and ensuring good quality superchilled beef.

Effect of Carcass Chilling on the Palatability Traits and Safety of Fresh Red Meat

Chilling procedures have been widely used in livestock abattoirs since the development of refrigeration systems. The major criteria when applying chilling regimes is not only complying with regulations, but economic concerns, and also meat safety and quality assurance requirements. Given recent developments, an updated review is required to guide the industry to choose the best chilling method and to inspire the development of new approaches to chilling. Thus in this paper, the quality and microbial safety of beef, lamb, pork, venison, and bison resulting from different chilling treatments has been reviewed, as well as the underlying mechanism(s) for the different impacts on meat quality traits as a result of different chilling regimes. The effect of fast chilling on the tenderness of beef and lamb is a focus, as some new findings, have recently been reported, while multistep chilling is highlighted as it incorporates the advantages of fast chilling to reduce carcass weight loss, resulting in similar quality improvements as found with slow chilling. It is, suggested, that if spray chilling can be combined with the second phase of multi-step chilling, it will benefit the meat industry in terms of both meat quality and safety. Future studies should focus on combinations of chilling methods with new technologies, such as medium voltage electrical stimulation, muscle stretching, or ultrasound and so on, to move meat quality and safety to a new level.

Effect of new generation medium voltage electrical stimulation on the meat quality of beef slaughtered in a Chinese abattoir

In this study, a medium voltage electrical stimulation (ES) system with three parameter combinations (A: 1A, 1.55 ms pulse width, 27 s; B: 0.55A, 1 ms pulse width, 34 s; C: 0.55A, 2 ms pulse width, 20s) were applied to beef carcases (n = 24; 319 ± 26.4 kg), in the context of a very slow pH decline rate in the abattoir. All the ES combinations significantly accelerated the rate of pH decline (reflected by temp@pH 6.0, i.e. temperature when pH drops to 6.0), resulting in a tenderness improvement even after 14 days ageing compared to the controls. Sarcomere length was not different between treatments and controls, and it was not a contributor to the tenderness improvement, instead, physical disruption revealed by transmission electron microscopic images may have led to the improvement. Retail colour was significantly improved by either combination B or C after 7 days of ageing. Combination B shows the most promise for commercial application, however, verification on more animals is required before commercial adoption.

Use of electrical stimulation and chilling to enhance meat tenderness of heavy lambs

Pouliot, E., Gariépy, C., Thériault, M. and Castonguay, F. W. 2014. Use of electrical stimulation and chilling to enhance meat tenderness of heavy lambs. Can. J. Anim. Sci. 94: 627–637. The aim of this study was to determine if electrical stimulation and chilling can modulate pre-rigor pH–temperature dynamics in order to enhance meat tenderness of heavy lambs produced in Quebec and determine if there is an optimum carcass temperature window to reach pH 6.0. A total of 128 heavy lambs (fasted body weight between 38 and 52 kg) were selected at the abattoir over 8 slaughter days (16 lambs d–1) and assigned to four processing treatments in a 2×2 factorial design: electrical stimulation (ES) or not (NES) and normal (NC) or slow (SC) chilling. Slow-chilled carcasses stayed warmer during the first 12 h postmortem (P<0.001), but reached the same temperature as NC ones thereafter. They also had a lower pH between 2 and 12 h (P<0.05). Stimulated carcasses had a lower pH than NES throughout the first 24 h postmortem (P<0.001), while ultimate pH was similar (P=0.738). Shear force values were improved (P<0.001) by both ES and aging as expected, although chilling had no effect (P=0.400). Stimulation×aging interactions for shear force values (P=0.019) and myofibrillar fragmentation index (P=0.097) indicate that aging began earlier following ES. Sarcomeres were longer for ES compared with NES carcasses (P<0.001) indicating that the latter were subject to cold shortening. Meat from NES carcasses was more prone to be tough, although an important part of NES carcasses provided tender meat. This illustrates the importance of individual variations on tenderness and the multiplicity of factors involved in its development. No optimal window was observed for temperature at pH 6.0.

Effects of low-voltage electrical stimulation and aging on lamb meat quality

Pouliot, E., Gariépy, C., Thériault, M., Avezard, C., Fortin, J., Simmons, N. J. and Castonguay, F. W. 2012. Effects of low-voltage electrical stimulation and aging on lamb meat quality. Can. J. Anim. Sci. 92: 59–66. The aim of this study was to evaluate the effect of electrical stimulation (ES) and aging time on meat quality of heavy lamb as produced in Quebec. Seventy-six Suffolk-sired crossbred male lambs were slaughtered at a target weight of 50±2 kg. Half of them were electrically stimulated (ES vs. control) at 5–10 min postmortem (21 V; 0.25 A; 60 s). Postmortem pH decline and temperature were monitored. After carcass cutting, longissimus dorsi sections were assigned to aging periods of 1, 3 or 8 d. Temperature decline was the same for both treatments (P=0.749). However, ES carcasses always had a lower pH value than controls during the first 24 h (P<0.001) while the ultimate pH was equivalent (P=0.803). Tenderness, as assessed by either Warner-Bratzler shear force (39 carcasses) or sensory evaluation (35 carcasses) was enhanced by both ES (P<0.001) and aging (P<0.001). At each aging time, tenderness was greater for ES meat. In addition, only 3 d of aging were necessary for ES meat to achieve the tenderness level attained by the controls after 8 d. Sarcomeres were longer (P<0.001) in ES meat than in controls while myofibrillar fragmentation index was not affected by ES treatment (P=0.743). Electrical stimulation also had small effects on color parameters (a*, b* and L*; P<0.01) and flavor (P=0.04). These results provide the first evidence that tenderness of the meat from heavy lambs produced and processed in Quebec could be enhanced by ES, mostly through cold shortening reduction.

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

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.

Processing technology changes in the Australian sheep meat industry: an overview

Over the last 20 years the Australian sheep industry, particularly the lamb meat sector, has undergone a major change in focus such that consumer requirements are a paramount determinant for production and processing developments. As a result automatic accurate methods of measuring carcasses for traits like fatness and meat yield have been important to aid a reduction by industry in carcass fat levels in line with domestic and international consumer demand. This occurred while carcass weight increased due to a range of genetic and production factors implemented on-farm. Further to this in the last 5–7 years there has been a dramatic increase in the adoption of electrical technologies based on new methodologies with a shift in focus onto eating quality. Underlying this new approach was the electrical stimulation of individual carcasses on segmented electrodes in a dose-responsive way with electricity that has short pulse widths and low to medium voltages and is thus much safer than the original high voltage systems. This technology allowed stimulation units to be fitted into abattoirs where this was not previously possible and validation showed that the technology could reduce toughness in lamb destined for the domestic market and some export markets. More recent technology to stretch and shape cuts shows promise for improving both the quality and product range from sheep and lamb carcasses. The industry continues to focus on meat quality and has shown a significant increase in exports, while maintaining per-capita domestic consumption at record retail prices. This indicates an industry where research investment across the board has shown significant returns.

Quality of lamb meat from the Information Nucleus Flock

The effects of production and processing factors on tenderness, and colour of lamb meat produced from 7 locations as part of the Australian Sheep Industry CRC’s Information Nucleus flock were investigated, using data from 2052 lambs slaughtered in 2007. At 24 h post-slaughter, samples of m. longissimus lumborum (LL) and m. semimembranosus (SM) were collected for measurement of intramuscular fat (IMF), myoglobin, iron and copper and fresh meat colour (L*, a*, b*) and pH at 24 h measured on the LL. pH and temperature measurements made pre-rigor were used to calculate the pH at 18°C. Tenderness was measured by LL shear force at days 1 (SF1) and 5 (SF5) post-slaughter, the shear force difference (SF-diff) and SM compression and collagen concentration were determined. Retail colour stability was assessed using over-wrapped LL under simulated retail display for 3 days, according to the change in the oxymyoglobin/metmyoglobin ratio. All traits were affected by flock and date of slaughter (P < 0.001). After 4 days of ageing, 70–95% of the LL samples from all flocks, except for one, had acceptable tenderness for consumers based on their shear force. Low IMF, high LL pH at 18°C and high pH at 24 h increased SF1 and SF5 and also had an effect on SF-diff (P < 0.001). The retail colour of 44.8% of the samples on day 3 of retail display were lower than acceptable. Retail colour was influenced by IMF, pH18 and the concentration of iron and copper (P < 0.001). In conclusion, breeding and management practices that increase muscle IMF levels and reduce ultimate pH values and processing practices that result in moderate rates of pH fall post-slaughter, improve the tenderness of lamb. Extension of retail colour stability may be antagonistic to traits associated with tenderness and nutritional traits, particularly IMF and mineral levels.

Influence of finishing systems and sampling site on fatty acid composition and retail shelf-life of lamb

Thirty 7-month-old crossbred lambs (Poll Dorset × Border Leicester × Merino) finished over 5 weeks on either low quality pasture or grain-with-hay on a farm in southern Victoria were assessed for carcass parameters, muscle fat composition and retail colour stability. Lambs on the grain diet had a mix of barley grain (80%) and lentils (20%) at 800 g/head.day (air-dry basis ~ad libitum) with cape weed (Arctotheca calendula) hay available at all times. Lambs under grazing had predominantly rye grass (Lolium perenne) and barley grass (Hordeum leporinum) available ad libitum. Carcass weight tended to be higher (P = 0.14) in grain-fed lambs than in grass-fed lambs, but fatness indicated by GR (total muscle + fat tissue thickness at 11 cm from midline) did not differ between feeding systems. Fatty acid composition was determined in the loin from the forequarter (M. longissimus thoracis) and lumbar (M. longissimus lumborum) regions and from the leg region (M. semimembranosus). This showed that grain-finished lamb had higher muscle fat (P < 0.001) and omega-6 fatty acid (P < 0.001) content. Alpha-linolenic acid, eicosapentaenoic acid (EPA) or total omega-3 fat did not differ (P > 0.05) between feeding groups. Saturated fatty acids were greater (P < 0.01) in both loin sampling sites than the leg. The levels of EPA, docosahexaenoic acid and docosapentaenoic acid were lower (P < 0.01) in the forequarter (9%) or lumbar (11%) sites than the leg sampling site. The distribution pattern of fatty acids across the three sampling sites did not differ between feed types. Retail colour stability determined over 4 days of display (only performed in muscle from the lumbar site), evaluated by the redness (HunterLab a*-value) and metmyoglobin formation (reflectance ratio at 630 : 580-nm wavelengths) was superior for grass-fed lamb compared with short-term grain-finished lamb. The results demonstrate that the health claimable omega-3 fat mainly EPA or total omega-3 fat content in lamb was not altered by short-term grain finishing compared with lamb finished under pasture grazing conditions.

Case studies demonstrating the benefits on pH and temperature decline of optimising medium-voltage electrical stimulation of lamb carcasses

The efficacies of electrical stimulation practices at Australian abattoirs that process significant proportions of Australian lamb and sheep meat were assessed. Several abattoirs used medium-voltage electrical stimulation system (MVS) units suboptimally and many carcasses at these abattoirs exhibited a poor rate of pH decline and, consequently, a low proportion of carcasses attained pH 6 at a carcass temperature of 18−35°C, according to Sheep Meat Eating Quality pH–temperature guidelines as adopted by Meat Standards Australia. In the present communication, we describe the causes of suboptimal results with electrical stimulation and discuss procedures for optimising the stimulation dose delivered by MVS units. Carcass pH responses to various levels of current and pulse width were assessed to determine the best MVS settings for individual abattoirs. The MVS units at the abattoirs involved in the present study have now been programmed for optimal efficacy and carcass quality will be monitored on an ongoing basis. Evaluation of methods for assessing the proportion of carcasses that fall within the optimum pH–temperature window showed that a random regression model is more accurate than the current approach.

Modelling muscle energy-metabolism in anaerobic muscle

A mathematical model of anaerobic muscle energy-metabolism was developed to predict pH and the concentrations of nine muscle metabolites over time. Phosphorous-31 Nuclear Magnetic Resonance was used to measure time-course data for some phosphate metabolites and pH in anoxic M. semitendinosus taken from three slaughtered sheep. Muscles were held at 35 degrees C during the experiment. Measurement commenced 25 min post mortem and concluded before rigor mortis. The model was fitted to these data within experimental error, by simultaneously varying model parameter values and initial substrate concentrations. The model was used to simulate the period from death until metabolic activity ceased, in order to predict the different stages of metabolic response to anoxia. The model suggested that alkalinisation would occur in all three muscles in the first few minutes after the onset of anoxia, followed by a steady decline in pH. For two of the muscles this decline continued until rigor, with final pH values of 5.60 and 6.07. For the other muscle, pH reached a low of 5.60 near rigor but then increased to a final value of 5.73. A rise in pH after rigor has been observed but not previously explained in the literature. The modelling results suggest it was caused by the alkalising effect of adenosine monophosphate deamination being greater at low pH than the acidifying effect of inosine monophosphate dephosphorylation.