New electrical stimulation technologies for sheep carcasses New electrical stimulation technologies for sheep carcasses

2005 ◽  
Vol 45 (5) ◽  
pp. 575 ◽  
Author(s):  
F. D. Shaw ◽  
S. R. Baud ◽  
I. Richards ◽  
D. W. Pethick ◽  
P. J. Walker ◽  
...  

High voltage electrical stimulation applied to the lamb carcass at the end of the dressing procedure often leads to an improvement in overall product quality by reducing the incidence of toughness. It would be advantageous if the same results could be consistently achieved with the use of lower, safer, voltages — medium voltage electrical stimulation. Experiments were conducted to determine the effect of medium voltage electrical stimulation applied to wool-on carcasses on meat quality as assessed using the Sheep Meat Eating Quality protocols. A further experiment examined the interaction of electrical stimulation and meat aging time on the consumer acceptance of lamb meat. In the first experiment, 3 treatments: control (non-stimulated), medium voltage electrical stimulation (applied to the wool-on carcass) and high voltage electrical stimulation (applied at the completion of dressing) were examined. Samples of the loin (LTL) and rump (GM) muscles were evaluated by consumers using Sheep Meat Eating Quality protocols. For both muscles, the consumers gave higher scores for tenderness, juiciness, flavour and overall acceptability to the stimulated product (P<0.001). There were no statistically significant differences between the 2 stimulation treatments. The second experiment was conducted at a commercial lamb-processing abattoir that had installed a prototype automated electrode system designed to work at chain speed. Lambs received either no stimulation (control), low current medium voltage electrical stimulation (constant current 300 mA peak, 15 Hz, maximum voltage 550 V peak) or high current medium voltage electrical stimulation (constant current 600 mA peak, 15 Hz, maximum voltage 550 V peak) immediately after sticking. Electrical stimulation improved both the objective and sensory (Sheep Meat Eating Quality) eating quality attributes of lamb loin muscle when assessed following 2 days of ageing. When expressed according to consumer satisfaction rating, 30, 37 and 70% of the loins receiving low, high or no electrical stimulation, respectively, were rated as unsatisfactory at 2 days of ageing. At 4 days of ageing no loins from carcasses in the low stimulation treatment were rated by consumers to be unsatisfactory (P<0.05) compared with either non-stimulated (40%) or high-stimulated loins (35%). With respect to the effects of aging meat, electrical stimulation improved the consumer score at 2 days post-stunning by 8.9 and 4.7 points for tenderness and overall liking, respectively. Further linear improvements due to aging were similar for both electrical stimulation and unstimulated products. Under conditions of no electrical stimulation used in this experiment, 10 days aging results in tenderness and overall liking scores greater than 60 and with ES similar scores are achieved in 5 days. Consumer scores over 60 greatly reduce the chance of meat being classified as unsatisfactory.

2010 ◽  
Vol 50 (12) ◽  
pp. 1107 ◽  
Author(s):  
K. L. Pearce ◽  
R. van de Ven ◽  
C. Mudford ◽  
R. D. Warner ◽  
J. Hocking-Edwards ◽  
...  

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.


2005 ◽  
Vol 45 (5) ◽  
pp. 561 ◽  
Author(s):  
J. M. Thompson ◽  
D. L. Hopkins ◽  
D. N. D'Souza ◽  
P. J. Walker ◽  
S. R. Baud ◽  
...  

The impact of processing factors on sheep meat eating quality was investigated in an experiment in which stimulation (stimulation and no stimulation), chilling rate (fast and slow chilling) and carcass suspension (tenderstretch and normally hung by Achilles tendon) treatments were overlaid on 80 lamb and 40 mutton carcasses processed over 2 days, at 2 different abattoirs. Within each carcass, 3 muscles (M. longissimus thoracics et lumborum, biceps femoris and serratus ventralis) were collected from both sides and aged for 2 of 3 ageing periods (2, 5 or 14 days), before sensory testing for tenderness, juiciness, like flavour and overall liking, using a consumer taste panel. Processing treatments of stimulation and chilling were variable in their effect on the rates of pH and temperature decline and temperature at pH 6 (temp@pH6), between the 4 slaughter groups. Therefore chilling rate and electrical stimulation were considered as tools by which temp@pH6 could be manipulated, rather than as treatment effects per se. Age category (lamb or mutton) had the largest impact on tenderness score, followed by muscle, ageing and carcass suspension. There were significant interactions for tenderness and overall liking scores between muscle × ageing, age category × muscle and carcass suspension × muscle (P<0.05). The magnitude of the tenderstretch advantage in sensory scores was a function of temp@pH6. In normally hung carcasses, the highest sensory scores were evident at about 21°C temp@pH6, with a decrease in sensory scores at high (>30°C) or low (<10°C) temp@pH6. There was a tendency for sensory scores (particularly for the like flavour score) to decline for the biceps femoris when it was stored for extended periods (14 days).


2005 ◽  
Vol 45 (5) ◽  
pp. 585 ◽  
Author(s):  
H. A. Channon ◽  
S. R. Baud ◽  
P. J. Walker

This study was conducted to determine the effect of electrical stimulation [control or stimulated (applied for 20 s using a constant current of 600 mA peak and maximum voltage of 550 V with a frequency of either 14 Hz or 10 Hz], ageing period (7, 21 or 35 days) and packaging method [modified atmosphere packaging (MAP) or overwrapped] on the retail display life of lamb [bone-in loin (M. longissimus thoracis et lumborum) chops and boneless leg steaks from the knuckle (M. quadriceps femoris)]. The colour and retail acceptability of lamb cuts were assessed both subjectively and objectively, using a chromameter, after 3 (midpoint of commercial retail display life; midpoint) and 5 (endpoint of commercial retail display life; endpoint) days for overwrapped product and at 5 (midpoint) and 9 (endpoint) days for MAP product. Retail display life of lamb (assessed both objectively and subjectively) was improved (P<0.001) by packaging lamb cuts into modified atmosphere compared with overwrapped lamb cuts. Electrical stimulation and length of ageing period before preparation into retail cuts did not influence colour or retail display life of lamb loin chops or leg steaks. Although the interaction of ageing period and packaging method were significant (P<0.001) for subjective colour, acceptability and retail grade of lamb loin chops and leg steaks at the midpoint of display life, these effects were inconsistent. This study highlighted that further work is necessary to determine potential means of improving the colour stability of lamb to enhance its retail display life, particularly cuts of the M. quadriceps femoris.


2005 ◽  
Vol 45 (5) ◽  
pp. 499 ◽  
Author(s):  
D. L. Hopkins ◽  
P. J. Walker ◽  
J. M. Thompson ◽  
D. W. Pethick

The effect of type of lambs and hoggets on eating quality was evaluated using the M. longissimus lumborum (LL) and the M. biceps femoris (BF) from 210 animals. The animals comprised 7 types as follows: Poll Dorset or White Suffolk × (Border Leicester × Merino) (second cross unweaned lambs, mixed sex, 3–5 months of age); Poll Dorset × (Border Leicester × Merino) (second cross weaned lambs, mixed sex, 9–12 months of age); Border Leicester × Merino (BLM; first cross weaned lambs, mixed sex, 9 months of age); Poll Dorset or White Suffolk × Merino (PDM; first cross weaned lambs, wethers, 12 months of age); Merino × Merino (weaned wether lambs, 9–12 months of age); Border Leicester × Merino (BLM; first cross hoggets, mixed sex, 20 months of age); and Poll Dorset or White Suffolk × Merino (PDM; first cross hoggets, wethers, 16 months of age). The animals were sourced from a number of different properties in New South Wales (NSW) (n = 120) and Victoria (n = 90). Each carcass was subjected to high voltage stimulation (700 V) within 1 h of slaughter. All meat was aged for 5 days before freezing and was subsequently tested by consumers on a 0–100 scale for a number of attributes after cooking using a grilling procedure. The LL from sucker lambs had the lightest colour (highest L* values) with the hoggets having the darkest colour in the NSW group with differences less apparent in the Victorian group. Muscle from first cross and Merino weaned lambs had consistently higher pH levels across the 3 muscles tested (LL; M. semimembranosus; M. semitendinosus) for the NSW group with no differences detected in the Victorian group. LL meat from second cross sucker and first cross (BLM and PDM) weaned lambs had the highest overall liking score, with that from second cross weaned lambs, BLM hoggets and Merino lambs scored as intermediate, while meat from the PDM hogget group had the lowest overall liking score. A similar outcome was found for the other sensory attributes with differences between types being lower for juiciness compared with overall liking scores but they were of a similar ranking. For the BF there was some re-ranking of the overall liking scores compared with the LL, with meat from suckers and first cross PDM lambs and hoggets being intermediate in score while second cross weaned lambs and first cross BLM lambs had the highest scores. The BF from hoggets (BLM) and Merino lambs were given the lowest scores. The lower juiciness score for sucker BF contributed to this change in ranking compared with the LL.


2005 ◽  
Vol 45 (5) ◽  
pp. 483 ◽  
Author(s):  
A. B. Pleasants ◽  
J.M. Thompson ◽  
D.W. Pethick

A probabilistic model of consumer perception of sheep meat eating quality is constructed on the basis of a sensory score derived from consumer evaluation of tenderness, juiciness, flavour and overall liking. The model includes consideration of the variability of the sensory score within a mob, the probability that meat with a given sensory score will be perceived by the consumer as correctly classified, and the distribution of the average sensory score within an eating quality grade. Based on this information the model can calculate the frequency with which sheep meat given a sensory score that will fail to meet the consumer expectation of the allocated eating quality grade. The model provides a basis for integrating the information gathered on sheep meat eating quality to formulate a method of classification and to quantify the reliability of this classification. This information can be applied in a variety of ways to evaluate the efficacy, financial or otherwise, of a retailer adopting a given sheep meat eating quality classification based on the nominated eating quality score.


2005 ◽  
Vol 45 (5) ◽  
pp. 593 ◽  
Author(s):  
O. A. Young ◽  
D. L. Hopkins ◽  
D. W. Pethick

The sheep meat eating quality research program has identified a number of outcomes and critical control points in the supply chain from live sheep genetics to cooked meat. The critical control points, which are largely independent of each other, can be translated into quality management systems to increase average eating quality of all cuts and lower variability. The choice of sire was a critical control point in that selecting for high growth rate and muscling can adversely affect eating quality. The challenge is to make sure that high yield traits are not promoted at the expense of eating quality. Animal age was a critical control point but it was clear that the definition of hogget could be revised to include slightly older animals with teeth in eruption but not in wear. Moreover, M. longissumus dorsi from older animals had only slightly lower eating quality than that from lamb such that this cut could be positioned as a premium product at all maturities, complementing the universally tender muscle psoas major. There was no doubt, however, that over all muscles, lamb remained the premium product. The critical control point for nutrition is that it be adequate, typically to ensure growth of at least 50 g/animal.day. Meat quality is improved through higher glycogen concentrations in muscles at slaughter, higher intramuscular fat content, and possibly reduced collagen crosslinking. Critical control points between muster and slaughter are more difficult to define but are generally aimed at stress reduction to minimise occurrence of the high ultimate pH condition. They include avoiding temperature extremes, loud noises and use of dogs, implementation of good lairage design and the use of skilled animal handlers. Stress is best monitored by ultimate pH measurements in abattoirs, rather than at remote points down the supply chain. After slaughter, the use of electrical stimulation to accelerate post mortem glycolysis is a critical control point. Its use is indicated where 2 conditions are simultaneously met: carcasses are Achilles-hung throughout processing, and the meat is destined for early consumption, as would normally be the case for the domestic market. By accelerating glycolysis, the temperature at rigor can be optimised for rapid tenderisation of low-connective tissue muscles through ageing. The alternative to electrical stimulation of these muscles for the local market is Tenderstretch hanging where rapid ageing is less temperature dependent. Where electrical stimulation is applied the monitoring of its effects with a temperature probe and a pH metre is a critical control point. Even where stimulation is not applied, measurement of average muscle temperature and pH is useful for defining any process. This is because the first 24 h after slaughter sets the scene for later meat storage/distribution, which has its own critical control point: the temperature at which meat is held between abattoir and consumption. Where meat is destined for early sale, the temperature of processing and storage can and should be higher than where the meat is destined for long-term storage as in export markets. For early sale, rapid ageing to optimum eating quality is promoted by higher temperature (2–4°C), whereas for export sale, very cool meat will slowly age in the weeks before consumption while at the same time minimising spoilage and maximising display life. Thus, matching the time–temperature profile of processing and storage to a particular market is a critical control point. The retail end of the supply chain has its own control points, principally display temperature and choice of display packaging, which have major effects on chilled display life. The cooler the better. Compared with conventional overwrap packs, modified atmosphere packs extend display life by typically 80%. However, these more sophisticated packs cost more and will not suit all domestic retailers. The matching of muscles by age with recommended cooking method is a critical control point at retail for ensuring consumer satisfaction. The challenge is effective communication with consumers and is part of the wider challenge of effectively communicating quality-related information at all links of the supply chain.


2006 ◽  
Vol 46 (7) ◽  
pp. 869 ◽  
Author(s):  
K. L. Pearce ◽  
D. L. Hopkins ◽  
E. Toohey ◽  
D. W. Pethick ◽  
I. Richards

The current study evaluated the effectiveness of a medium voltage post-dressing electrical stimulation unit at different current and pulse width settings on pH decline. The objective was to optimise these settings to ensure that a high proportion of carcasses would reach pH 6.0 when the carcass was between 18–25°C according to the guidelines set by the Australian Sheep Meat Eating Quality (SMEQ) program. In the first experiment, 3 different current (400, 700 and 1000 mA) and pulse width (1, 2.5 and 5 ms) settings plus a control (0 mA and 0 ms) were applied to carcasses for 34 s at a frequency of 15 Hz with 7 sheep per treatment over 3 consignments (n = 210 carcasses). The pH–temperature decline was evaluated for all carcasses. Based on the SMEQ guidelines, 43% of stimulated carcasses reached a pH of 6.0 between a carcass temperature of 18–25°C, compared with 14% of unstimulated controls. Furthermore, 21% of carcasses reached a pH of 6.0 before the carcass temperature reached 25°C and 36% did not reach a pH of 6.0 by the time the carcass was 18°C. Alternatively, under the Meat Standards Australia (MSA) pH–temperature guidelines, carcasses should reach pH 6.0 between 12 and 35°C; 87% of stimulated carcasses reached a pH of 6.0 between 12–35°C, compared with 39% of unstimulated controls. One percent of carcasses reached a pH of 6.0 before the carcass temperature reached 35°C and 12% did not reach a pH of 6.0 by a carcass temperature by the time the carcass was 12°C. The abattoir in this study had a very fast chilling regime which resulted in carcasses reaching pH 6.0 at low temperatures and accounted for the low number of carcasses reaching a pH of 6.0 between 18–25°C. There was no effect of different current and pulse widths on the rate of decline, temperature at pH 6.0 or initial pH, which was attributed to the late application of electrical stimulation postmortem when muscle contraction is dependant on direct muscle stimulation. The combination of 2.5 ms and 1000 mA was the best performing treatment with respect to both SMEQ and MSA guidelines and the number of carcasses reaching the pH–temperature window. This treatment had the highest percentage of carcasses reaching the SMEQ window (60%) and MSA window (97%). Furthermore, it resulted in the lowest number of carcasses not reaching pH 6.0 by a carcass temperature of either 12 or 18°C, making it the most suitable to an abattoir with a fast chilling regime. Modulation and frequency manipulation of the segmented electrodes were assessed with the frequency manipulation resulting in the greatest stimulation response. Further work is needed to understand the effect of manipulating the frequency on the system overall or of the individual modules as well as changing the stimulation time.


2008 ◽  
Vol 48 (7) ◽  
pp. 898 ◽  
Author(s):  
R. H. Jacob ◽  
K. L. Pearce ◽  
N. Smith

Two experiments were done following installation of a new generation medium voltage electrical stimulation unit at a commercial lamb abattoir in Western Australia. The first experiment was designed to optimise settings in relation to rate of pH decline post mortem. The second experiment was designed to investigate the eating quality and visual appearance effects of the optimal setting. In the first experiment, nine different settings were compared with a control using 60 lamb carcasses from each of 10 different consignments. The rate of pH × temperature decline was optimal with a pulse width of 2.5 ms and a current of 1.2 A. In the second experiment, 80 lamb carcasses consisting of four carcasses from each of 20 consignments were examined for various eating quality parameters including sarcomere length, shear force, bloom colour and colour stability. Two of the lambs from each consignment were stimulated and two were not stimulated. Stimulation improved compliance with the Sheep Meat Eating Quality (SMEQ) pH × temperature ‘window’ for domestic and frozen product but not for long ship product. Colour was improved by electrical stimulation without changing colour stability. There was a small effect on sarcomere length and no effect of stimulation on shear force measured at day 1 and day 10 after slaughter.


2005 ◽  
Vol 45 (5) ◽  
pp. 517 ◽  
Author(s):  
D. W. Pethick ◽  
R. Davidson ◽  
D. L. Hopkins ◽  
R. H. Jacob ◽  
D. N. D'Souza ◽  
...  

The aim of this experiment was to test the effects of dietary treatment on sheep meat eating quality as perceived by untrained Australian consumers. Six-month-old Suffolk × Merino lambs (n = 192) were allocated to 1 of 4 nutritional treatments for 60–77 days and were fed: (i) an irrigated perennial ryegrass–clover–kikuyu sward; (ii) irrigated perennial ryegrass–clover–kikuyu pasture for 48–61 days then poor quality straw for the last 12–16 days; (iii) a mixed ration treatment consisting of a high-energy pelleted diet (40% barley grain, 30% wheat grain, 15% hay and 12% lupin grain); or (iv) irrigated pasture for 37–51 days followed by a moderate-energy pelleted diet (36% wheat grain, 35% hay and 24.5% lupin grain) for 23–26 days. The starting liveweight of lambs was 31.5–35.5 kg and the final hot carcass weight was 19–20 kg. The nutritional treatment finishing system employing straw feeding for the last 12–16 days was associated with a loss of liveweight during this period, a decreased tissue depth at the GR site and a decreased content of intramuscular fat and glycogen in muscle. Untrained Australian consumers were asked to rate samples (scale 0–100) of the M. longissimus thoracis et lumborum (LL) from lambs for tenderness, liking of flavour, juiciness and overall liking and then classify the meat as unsatisfactory, good everyday or better than everyday. Straw feeding was also associated with significantly reduced consumer scores for juiciness (P<0.05) and liking of flavour (P<0.10) with no changes in tenderness and overall liking. There was no significant difference in the consumer acceptance of the LL obtained from lambs finished on pasture v. grain-based diets. It is concluded that nutritional finishing systems should be selected to prevent animals from losing weight pre-slaughter and that decisions on pasture v. grain based feeding systems be based on the cost of production.


1987 ◽  
Vol 67 (3) ◽  
pp. 689-704 ◽  
Author(s):  
Z. J. HAWRYSH ◽  
F. H. WOLFE

The quality characteristics of biceps femoris (BF), longissimus (L) and pectoralis profundis (PP) roasts obtained from young and mature cow carcasses subjected to low voltage (110 V) electrical stimulation (ES) were determined. ES was applied with a steel busbar rectal probe for 2 min. Evaluations were conducted on meat obtained from young control sides (no ES) aged 48 h, from young and mature sides (no ES) aged 6 d and from young and mature ES sides aged 48 h. ES caused a reduction (P < 0.001) in BF muscle pH at 1 and 4 h postmortem. Except for the pH differences in L muscle of young cows at 24 h, there were no differences in L muscle pH values due to ES for either young or mature cows. At 24 h, the pH of muscles from all carcasses was about 5.6. Cooking losses did not appear to be affected by either ES or increased aging in young control roasts. For both young and mature BF and L roasts, trained panelists generally did not detect significant effects due to ES. Except for differences in OTMS-Warner Bratzler shear values for mature PP samples, objective measurements for all roasts show no significant effects due to ES. Thus, no differences in cooking and eating quality of BF, L and PP roasts were found due to the application of low-voltage ES via the busbar rectal probe. Increasing postmortem aging time from 48 h to 6 d for young control carcasses did not influence roast quality. Animal maturity had some significant effects on the quality of all roasts. Key words: Low-voltage electrical stimulation, beef quality


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