Oxygen concentration in MAP can be reduced with minimal impact on eating quality of lamb

This study evaluated the impact of high oxygen modified atmosphere packaging (MAP) in four different combinations, 80 % oxygen and 20 % carbon dioxide (MAP80), 40 % oxygen, 20 % carbon dioxide and 40 % nitrogen (MAP40(20CO2)), 40 % oxygen, 60 % carbon dioxide (MAP40(60CO2)), and vacuum skin packaging (VSP) under different retail display times (3 or 8 days) on the sensory scores of lamb meat. Untrained consumer sensory scores for overall liking, tenderness, juiciness and liking of flavour were assessed on the M. longissimus lumborum (loin) and M. semimembranosus (topside) of 144 lambs. In general, MAP40(20CO2) samples received higher sensory scores than MAP80 (P < 0.05). While the high carbon dioxide MAP mixture MAP40(60CO2) scored similar to MAP80 (P > 0.05). Therefore, MAP40(20CO2) minimised the detrimental effects on eating quality and is a viable alternative to the widely used MAP80. However, the highest eating quality scores were still obtained with VSP (P < 0.05).

The construction of a sheepmeat eating quality prediction model for Australian lamb

The current sheep Meat Standards Australia (MSA) model is a pathways system designed to improve the overall eating quality of Australian lamb, yet it is unable to predict individual consumer-based eating quality scores for specific cuts. This paper describes the methodology of using consumer sensory scores to create an objective composite eating quality prediction score linked to individual quality grades for different cuts. This methodology accounts for objective carcass measures that are being commercialised within the industry, such as intramuscular fat percentage and a measure of lean meat yield percentage. The model demonstrated that through utilising these carcass grading traits, an eating quality prediction can be made with an accuracy of 75 % and 72 % for the grill and roast cooking method respectively, however individual consumer variation remained substantial. The model will allow the supply chain to allocate cuts to different marketing strategies (branding) based on their eating quality performance whilst also reducing the chances of consumers being offered products that do not meet their expectations.

Meat tenderness in Australian lamb: Data editing, environmental variation and their effects in genetic parameter estimation

Breeding for meat quality increases the value of lambs and requires reliable genetic parameters to achieve balanced genetic progress. Meat tenderness, accomplished by selecting for lower shear force, is an important eating quality trait because of its relationship with consumer satisfaction. Factors influencing shear force, include the pH and temperature decline post-mortem which can contribute towards higher shear force values and increased variation across contemporary groups. This study explored if genetic parameters for shear force change when post slaughter covariates and heterogeneous variance are corrected for, using data from 32,223 animals from different sheep breeds. Results showed that removing extreme individuals and contemporary groups with high mean shear force values reduced residual variance, followed by a smaller reduction in additive genetic variance and little effect on heritability. Results show that edited data performed better at predicting progeny performance and reduced potential bias introduced in the genetic evaluation due to data quality. The effect of including post-slaughter covariates in the genetic analysis was tested by estimating different model predictability through regression of estimated breeding values against offspring performance, showing that the model including hot carcass weight performed better followed by the one including both carcass weight and C-site fat depth. Our results highlight that historic and current in-plant recording practices do not provide the capacity to account for non-genetic factors associated with abattoir environment that might be impacting the ability to accurately calculate shear force breeding values. In that sense, genetic evaluation can be improved by applying more rigorous data editing.

Ageing of Australian lamb beyond 14 days does not further improve eating quality

Limited studies are available assessing the impact of extended ageing on lamb eating quality of a wide range of cuts. From lamb (n = 153) and young mutton (n = 40) carcasses, seven cuts (eye of rack, eye of shoulder, knuckle, loin, outside, rump and topside) were collected and aged based on three ageing times (5, 14 or 21 days). Additionally, residual glycogen was determined from the loin at the corresponding ageing time. Untrained consumers assessed samples for tenderness, juiciness, flavour liking and overall liking. Increasing ageing time from 5 to 14 or 21 days significantly improved cut eating quality; however, ageing beyond 14 days showed no additional benefit. The ageing effect reduced when corrected for pH and temperature measurements, confirming ageing can improve eating quality when pH and temperature variation exists. Loin residual glycogen had no impact on eating quality at each ageing time. Our results confirm the importance of establishing optimum ageing times for cuts to ensure the highest consumer acceptability.

Ultra-wideband microwave precisely and accurately predicts sheepmeat hot carcase GR tissue depth

A portable ultra-wideband microwave system (MiS) coupled with an antipodal slot Vivaldi patch antenna (VPA) was used as an objective measurement technology to predict sheep meat carcase GR tissue depth, tested against AUS-MEAT national accreditation standards. Experiment one developed the MiS GR tissue depth prediction equation using lamb carcasses (n = 832) from two slaughter groups. To create the prediction equations, a two layered machine learning stacking ensemble technique was used. The performance of this equation was tested within the dataset using a k-fold cross validation (k = 5), which demonstrated excellent precision and accuracy with an average R2 of 0.91, RMSEP 2.11, bias 0.39 and slope 0.03. Experiment two tested the prediction equation against the AUS-MEAT GR tissue depth accreditation framework which stipulates predictions from a device must assign the correct fat score, with a tolerance of ±2 mm of the score boundary, and 90% accuracy. For a device to be accredited three measurements captured within the same device, as well as measurements across three different devices, must meet the AUS-MEAT error thresholds. Three MiS devices scanned lamb carcases (n = 312) across three slaughter days. All three MiS devices met the AUS-MEAT accreditation thresholds, accurately predicting GR tissue depth 96.1-98.4% of the time. Between the different devices, the measurement accuracy was 99.4-100%, and within the same device, the measurement accuracy was 99.7-100%. Based on these results MiS achieved AUS-MEAT device accreditation as an objective technology to predict GR tissue depth.

The carcass characteristics and quality of meat from lambs grazing perennial wheat with different companion legumes (clover, serradella, lucerne) or a mineral supplement

This study compared carcasses as well as the quality and mineral concentration of meat from lambs extensively grazing perennial wheat with clover (PW + C), serradella (PW + S), lucerne (PW + L), or a mineral salt supplement (PW + Min). A split-plot design was used, wherein 3 crossbred ewe lambs (n = 72 in total) (sub-plots) grazed each of 4 forage types (plots), that were replicated across 6 locations (blocks). The feeding study concluded after 96 d, when all the lambs were slaughtered. The left longissimus lumborum muscles (LL) were collected and wet aged for either 5 or 56 d post-mortem. Lambs grazing PW + Min were found to produce carcasses with lower dressing percentage values to those grazing the other forage types (P = 0.037). The LL of lambs grazing PW + L had the lowest crude protein values (P = 0.015). Forage type by ageing period interactions did not affect meat quality. The 56 d ageing period resulted in higher purge loss (P < 0.001) and TVB-N values (P < 0.001) and a decline in shear force (P < 0.001) compared to the 5 d ageing period. The other carcass and meat quality parameters were not affected by forage type; including hot carcass weight, pH decline parameters, eye muscle area, cooking loss, intramuscular fat, sarcomere length, colour stability, and concentrations of calcium, iron, magnesium, sodium, and zinc in the LL. These findings confirm that perennial cereal production systems, that include legume forages with contrasting protein, energy, and micronutrient profiles, can deliver comparable lamb carcasses and meat quality.

The Impact of Genetic and Non-Genetic Factors on Lamb Loin Shear Force

Shear force is commonly used to evaluate tenderness, one of the most crucial eating quality aspects of sheep meat. The effect size of various factors on tenderness is still unknown. Studies have suggested that both genetic and environmental factors contribute to the variation in meat tenderness, and there are possible interactions between these factors. An extensive data set (n = 23,696) was analyzed to examine genetic and non-genetic influences on the shear force at 5 days postmortem (SF5). SF5 was measured on lamb loins (Longissimus lumborum) taken from lambs reared over 12 years at eight sites across Australia. The results showed that all carcass traits had a significant (p < 0.001) impact on SF5, with the largest effect on SF5 associated with intramuscular fat (IMF %) (f = 1035). There was also a significant effect of sex, cold shortening at 18 °C, sire type and cohort on SF5 (p < 0.001), with a large variation observed between the minimum cohort at 15.9 ± 1.5 N and maximum at 51.2 ± 2.1 N. In conclusion, a complex matrix of production, processing and genetic factors impact lamb tenderness as measured by shear force. This experiment helps identify the size of the contribution of these factors towards lamb tenderness, enabling the sheep industry to enhance consumers' satisfaction.

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.

Predicting lamb carcase composition from tissue depth measured at a single point with an ultrawide-band microwave scanner

This study evaluated the ability of portable ultra-wide band microwave system (MiS) to predict lamb carcase computed tomography (CT) determined composition % of fat, lean muscle and bone. Lamb carcases (n = 343) from 6 slaughter groups were MiS scanned at the C-site (45 mm from spine midline at the 12th /13th rib) prior to CT scanning to determine the proportion of fat, muscle and bone. A machine learning ensemble stacking technique was used to construct the MiS prediction equations. Predictions were pooled and divided in 5 groups stratified for each CT composition trait (fat, lean or bone%) and a k-fold cross validation (k = 5) technique was used to test the predictions. MiS predicted CT fat% with an average RMSEP of 2.385, R2 0.78, bias 0.156 and slope 0.095. The prediction of CT lean% had an average RMSEP of 2.146, R2 0.64, bias 0.172 and slope 0.117. CT bone% prediction had an average RMSEP of 0.990, R2 0.75, bias 0.051 and slope 0.090. Predictions for CT bone% met AUS-MEAT device accreditation error tolerances on the whole range of the dataset. Predictions for CT lean% and fat% met AUS-MEAT error tolerances on a constrained dataset.

Eating Quality of Australian Grass and Grain-Fed Lamb Equally Rated by US Consumers

Anecdotal suggestions that US consumers perceive Australian sheepmeat as more "gamey" or "stale" compared to US sheepmeat are potentially attributable to the extended chilled shipping times contributing to longer-aged meat and predominately pasture-fed grazing systems. This study evaluated the impact of diet and extended storage times on Australian sheepmeat using sensory scores as assessed by US consumers. Meat samples from Australian sheep (n = 80) fed a grass or grain diet were aged in a vacuum at 1-2 °C for 5, 21 or 45 days. Untrained consumers (n = 960) at Texas Tech University (Lubbock, Texas) assessed samples for overall liking, tenderness, juiciness and flavour using a scale from 1 (worst) to 100 (best). In general, US consumers scored grain- and grass-fed samples within the same storage period similarly (p > 0.05). Furthermore, storage from 5 to 21 days improved sensory scores by a maximum of 28.6 for tenderness for grass-fed outside cuts (p < 0.05), while storage for 21 to 45 days did not improve eating quality for most cuts of both diets (p > 0.05). This is an interesting finding for the Australian sheepmeat industry as long storage time has no negative effect on eating quality and US consumers enjoyed grass- and grain-fed sheepmeat equally.

Quantifying the Effect of Grilling and Roasting on the Eating Quality of Lamb Leg Muscles

Lamb eating quality was measured using untrained consumer sensory panels to determine the difference in intrinsic eating quality scores of grilled and roasted leg cut muscles. The Knuckle, Outside flat, and Topside from both legs of 65 mixed-sex lambs from diverse genetic backgrounds were prepared using alternative grill and roast cook methods. Each sample was eaten by 10 consumers and scored for tenderness, juiciness, flavor, and overall liking. All cuts scored higher (p < 0.001) when grilled compared with when roasted for all traits except for Topside tenderness. Grilled Knuckle scored higher than roast Knuckle by 13.6%, 23.9%, 14.4% and 15.8% for tenderness, juiciness, flavor, and overall liking, respectively. The grilled Outside flat scored higher than roast Outside flat by 14.1%, 27.1%, 10.9%, and 14.3% for tenderness, juiciness, flavor, and overall liking, respectively. Finally, grilled Topside scored higher than roast Topside by 21.3%, 7.4%, and 6.6% for juiciness, flavor, and overall liking, respectively. Carcass traits for intramuscular fat and shear force had a significant (p < 0.001) effect on all eating quality traits for both grill and roast cuts. Girth rib fat had a significant effect (p = 0.01) on tenderness and juiciness (p = 0.03) for Outside flat and Topside but had no effect (p > 0.05) on Knuckle for both grill and roast. This study identified that specific cooking methods can improve sensory traits for individual cuts and suggests that a cut-by-cook method eating quality model for sheepmeat can therefore increase consumer satisfaction.

Chinese Consumer Assessment of Australian Sheep Meat Using a Traditional Hotpot Cooking Method

Hotpot is a widely popular cooking method for sheepmeat in China. This study measured the sensory responses of 720 untrained Chinese consumers to Australian sheepmeat cooked using a hotpot technique with methods based on Meat Standards Australia protocols. Shoulder and leg cuts of 108 lambs and 109 yearlings were scored on tenderness, juiciness, flavour and overall liking with linear mixed effects models used to analyse the influence of muscle type and animal factors on these scores. On average, shoulder cuts were more palatable than legs cuts for all sensory traits (p < 0.01) and lambs compared to yearlings (p < 0.05). Intramuscular fat and muscularity were identified as strong drivers of eating quality (p < 0.05), with greater palatability for both cuts as intramuscular fat increased (range 2.5 to 7.5%), and muscularity decreased (as measured through loin weight adjusted for hot carcase weight). Consumers were unable to detect differences between animal sire type and sex in sheepmeat hotpot. These findings suggest shoulder and leg cuts performed comparatively well in hotpot compared to previously tested sheepmeat cooking methods and emphasise the importance of balanced selection for quality and yield traits to ensure that consumer satisfaction is maintained.

Bone mineral concentration predicted by dual energy X-ray absorptiometry and its relationship with lamb eating quality

Lumbar bone mineral concentration, as predicted by dual energy x-ray absorptiometry (DEXA), may reflect changes in lamb maturity and eating quality. New season (n = 60) and old season (n = 60) lambs were slaughtered and DEXA scanned at a commercial abattoir across 2 kill groups. The second lumbar vertebra was isolated from the spine for determination of calcium, phosphorus, and magnesium concentration (mg/g). The loin and rack cuts were collected for consumer sensory grilling and roasting analyses. Mineral concentration was significantly higher in old season lambs within kill group 1 (P < 0.05). DEXA was a positive predictor of phosphorus and calcium concentration, but only when DEXA lean % (P < 0.05) was included in the model. Calcium and phosphorus were significant positive predictors of overall liking scores (P < 0.05), but only for the rack roast. These effects became insignificant when DEXA lean % was included. These results suggest that DEXA values likely reflect changes in both DEXA lean % and bone minerals, and that DEXA lean % was the driver of eating quality, rather than maturity.

Consumer Perceptions of Meat Redness Were Strongly Influenced by Storage and Display Times

Lamb (n = 79) meat colour was scored by 879 untrained consumers using a scale of 0 (brown) to 100 (red). This consumer colour score (CCS) was obtained on m. longissimus lumborum (loin) and m. semimembranosus (topside), stored for short (5–7 days), medium (33–35 days), and long periods (110–112 days) and a retail display time of up to 4 days. Consumers perceived topside to be less red initially and changed from red to brown more rapidly when stored for the long-storage period (p < 0.01). Whereas, the initial CCS of loin samples were similar across the storage periods (p > 0.05). CCS and the instrument measure oxy/met (reflectance of light at wavelengths 630 nm and 580 nm) had a low correlation coefficient of 0.33 (p < 0.01). The propensity for lamb growth and leanness indicated by sire breeding values for lamb weight, eye muscle depth, eye muscle fat depth, and loin intramuscular fat had varied and inconsistent effects on CCS. Therefore, even the selection on CCS.

Post-mortem pH decline in lamb semitendinosus muscle and its relationship to the pH decline parameters of the longissimus lumborum muscle: A pilot study

This study compared longissimus lumborum (LL) and semitendinosus (ST) muscles, in 48 lamb carcasses, to determine their pH decline parameters and achievement of ideal pH criteria (hitting the window). These include the pH at temperature 18 °C (pH@18) and temperature at pH 6 (temp@pH6). No practical difference were found between muscles for pH@18 or the temp@pH6, although there were differences between the experimental carcasses evaluated. Indeed, for all but three carcasses, there were insignificant differences between the LL and ST in terms of their pH@18. This outcome suggests that the lower value and more accessible ST muscle can be measured to determine lamb carcass pH decline parameters, instead of the LL. Because of the scale of this study, additional investigation is advised prior to any adoption.

Prediction of lamb carcase C-site fat depth and GR tissue depth using a non-invasive portable microwave system

The experiment evaluated the ability of portable ultra-wide band microwave coupled with a Vivaldi patch antenna to predict carcase C-site fat and GR tissue depth. For C-site, 1070 lambs, across 8 slaughter groups were scanned and for GR, 286 lambs across 2 slaughter groups. Prediction equations for reflected microwave signals were constructed with a partial least squares regression two-components model and a machine learning Ensemble Stacking technique. Models were trained and validated using cross validation methods in actual datasets and then in datasets balanced for tissue depth. The precision and accuracy indicators of microwave predicted C-site fat depth across pooled and balanced datasets were RMSEP 1.53 mm, R2 0.54, and bias of 0.03 mm. The precision and accuracy for GR tissue depth across pooled and balanced datasets were RMSEP 2.57 mm, R2 0.79 and bias of 0.33 mm. Using the AUS-MEAT fat score accreditation framework this device was able to accurately predict GR 92.7% of the time.

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.

Influence of Demographic Factors on Sheepmeat Sensory Scores of American, Australian and Chinese Consumers

Along with animal production factors, it is important to understand whether demographic factors influence untrained consumer perceptions of eating quality. This study examined the impact of demographic factors and sheepmeat consumption preferences on eating quality scores of American, Australian and Chinese untrained consumers. M. longissimus lumborum (LL) and m. semimembranosus (SM) were grilled according to sheep Meat Standards Australia protocols and evaluated by 2160 consumers for tenderness, juiciness, flavour and overall liking. Linear mixed effects models were used to analyse the impact of demographic factors and sheepmeat consumption habits on eating quality scores. Consumer age, gender, number of adults in a household and income had the strongest effect on sensory scores (P ≤ 0.05), although, the impact was often different across countries. Frequency of lamb consumption had an impact on sensory scores of American, Australian and Chinese consumers but larger sample sizes in some underrepresented subclasses for Australian and Chinese consumers are needed. Results suggest it is important to balance sensory panels for demographic factors of age, gender, number of adults and income to ensure sensory preferences are accurately represented for these particular populations.

Genetic correlations between meat quality traits and growth and carcass traits in Merino sheep1

Genetic correlations between 16 meat quality and nutritional value traits and live weight at various ages, live ultrasound fat and muscle depth, carcass measures, and carcass dissection traits were estimated for Merino sheep in the Information Nucleus (IN). Genetic correlations between live weight at various ages and the carcass traits are also reported. The IN comprised 8 genetically linked flocks managed across a range of Australian sheep environments. Meat quality traits included between 1,200 and 1,300 records for progeny from over 170 sires for intramuscular fat (IMF), lean meat yield (LMY), shear force (SF5), pH, meat color, and meat nutritional value traits including iron and zinc levels and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. The genetic correlations indicated that selection of Merino sheep to either reduce fat or increase muscle using ultrasound assessments will result in little change in IMF and SF5. Myoglobin levels would tend to be reduced following selection for reduced ultrasound fat depth (0.35 ± 0.21, 0.43 ± 0.14), whereas increases in myoglobin levels would occur due to selection for increased ultrasound muscle depth (0.25 ± 0.24, 0.38 ± 0.15). Selection for increased live weight will result in favorable correlated responses in hot carcass weight (0.76 to 0.97), dressing percentage (0.13 to 0.47), and carcass muscle (0.37 to 0.95), but unfavorable responses of increases in carcass fatness (0.13 to 0.65) and possible small reductions in muscle oxidative activity (-0.13 ± 0.14 to -0.73 ± 0.33) and iron content (-0.14 ± 0.15 to -0.38 ± 0.16), and a possible deterioration of shear force from selection at later ages (0.15 ± 0.26, 0.27 ± 0.24). Negligible changes are generally expected for LMY and meat color traits following selection for increased live weight (most genetic correlations less than 0.20 in size). Selection for increased LMY would tend to result in unfavorable changes in several aspects of meat quality, including reduced IMF (-0.27 ± 0.18), meat tenderness (0.53 ± 0.26), and meat redness (-0.69 ± 0.40), as well as reduced iron levels (-0.25 ± 0.22). These genetic correlations are a first step in assisting the development of breeding values for new traits to be incorporated into genetic evaluation programs to improve meat production from Merino sheep and other dual-purpose sheep breeds.

Lamb Age has Little Impact on Eating Quality

There is an industry wide perception that new season lamb has better eating quality than old season lamb. This study aims to identify differences in consumer eating quality scores between two age classes in lamb. Consumer eating quality scores from eight cuts across the carcass were evaluated from new season (NS; n = 120; average age = 240 days) and old season lambs (OS; n = 121; average age = 328 days), sourced from four different flocks. Cuts were grilled (loin, topside, outside, knuckle and rump) or roasted (leg, shoulder, rack) and scored by untrained consumers for tenderness, juiciness, liking of flavour and overall liking. There was no difference in eating quality scores between the two age classes for the loin, leg, shoulder and rack. This was similarly shown in the topside with the exception of juiciness scores where NS lambs were higher than OS lambs. There was also a lack of age difference in the outside with the exception of flock 3 where NS lambs scored higher than OS lambs for all sensory traits. Across all sensory traits, OS lambs received on average 2.8 scores lower for the knuckle and 3.1 scores lower for the rump compared to NS lambs. These results show little difference in eating quality between NS and OS lamb, and highlight the potential to develop high quality OS or "autumn lamb" products, with a similar premium price at retail as NS lambs.

Electrical stimulation extends the time limits for very fast chilling of lamb loins

Context Very fast chilling (VFC) involves cooling meat to approximately –1°C before the onset of rigor, and offers potential benefits compared with conventional chilling that include accelerated tenderisation, improved shelf life and reduced inventory costs. However, the practical difficulties of achieving the required temperature profile prevents adoption of VFC commercially. Aims The objective of this study was to determine if electrical stimulation could be a way of making VFC easier to achieve for lamb meat. The hypothesis tested was that electrical stimulation would reduce the rate of chilling required with very fast chilling by accelerating the rate of pH decline post-mortem. Methods The experiment was a 2 × 3 factorial design whereby 54 loins from 27 lambs were allocated to one of six different treatments: no electrical stimulation and electrical stimulation, and chilling rates to reach −1°C at 1 h (Fast), 1.5 h (Moderate) and 2.5 h (Slow) post-mortem respectively. Key results Without electrical stimulation, shear forces were lowest for the Moderate chilling rate; but with electrical stimulation, consistently low shear force values were obtained with all chilling rates. Muscle pH depended on treatment, although this effect also depended on the time post-mortem. Shear force depended on chilling rate only when there was no electrical stimulation. Without electrical stimulation, the optimal chilling rate was the Moderate treatment. Effects on sarcomere length accounted for some, but not all, of the effects of treatment on shear force. Conclusions Electrical stimulation therefore reduced the chilling rate required to optimise tenderness with VFC, and could be a component of a practical VFC regime for lamb meat. Implications VFC could become a practical chilling method, but only when sensory evaluation supports the favourable shear force findings established in this study. This would require evaluation of VFC at a commercial scale.

Suckler Bulls Slaughtered at 15 Months of Age: Effect of Different Production Systems on the Fatty Acid Profile and Selected Quality Characteristics of Longissimus Thoracis

The objective was to compare the quality of beef from bulls reared in typical Irish indoor systems or in novel grass-based systems. Bulls were assigned to one of the following systems: (a) grass silage plus barley-based concentrate ad libitum (CON); (b) grass silage ad libitum plus 5 kg of concentrate (SC); (c) grazed grass without supplementation (G0); (d) grazed grass plus 0.5 kg of the dietary dry matter intake as concentrate (GC) for (100 days) until slaughter (14.99 months). Carcass characteristics and pH decline were recorded. Longissimus thoracis was collected for analytical and sensory analysis. Lower carcass weight, conformation and fatness scores were found for grazing compared to CON and SC groups. CON bulls had highest intramuscular fat and lighter meat colour compared with grazing bulls. The SC meat (14 days aged) was rated higher for tenderness, texture, flavour and acceptability compared with grazing groups. CON saturated and monounsaturated fatty acid (FA) concentration was highest, conversely, omega-3 FA concentration was higher for GC compared with CON, while no differences were found in polyunsaturated FA. In conclusion, while market fatness specification was not reached by grazed grass treatments, beef eating quality was not detrimentally affected and nutritional quality was improved.

Volatile Flavor Components as a Function of Electrical Stimulation and Chiller Aging for m. longissimus and biceps femoris of Hanwoo Beef

The aim of the study was to evaluate the effect of an early post-mortem low voltage electrical stimulation (ES) to localized part of carcasses [m.longissimus lumborum (LL) and m.biceps femoris (BF)] and determined the tenderness and flavor compounds of Hanwoo steers (n=16). Carcasses were stimulated within 30 min post-mortem for 60s using 60 volts and muscles aged 2 and 14 d. Degradation of Troponin-T were accelerated by ES and degraded little faster in BF muscle than LL. Level of free amino acid content of stimulated and aged muscles was significantly (p<0.05) greater than control for both muscles. Totally 63 volatile compounds were identified by using SPME-GC. The ES treatment significantly (p<0.05) affected the level of 20 volatile compounds of LL as well 15 volatiles in BF muscle along with total amounts of ketones, sulfur containing, pyrazines and furans. Low voltage ES could be applied to reduce the aging time and improve volatile flavor development by increasing important desirable volatile compounds such as 2-methylpyrazine, 2,5-dimethylpyrazines and 2-acetylthiazole etc. due to released free amino acids from protein degradation.

Initial Bloom Color is a Poor Predictor of Retail Color Stability in Lamb Loin Meat

The rapid browning of lamb meat on retail display reduces its appeal to consumers and thus the marketability of lamb meat. Predicting the rate of meat browning on retail display would allow retailers to effectively manage this issue. The ability of bloomed meat color at the start of retail display to predict meat browning over subsequent retail display was investigated in lamb loin meat. Mixed breed lambs (n = 4404) produced at 5 sites over 5 yr were slaughtered at ∼23kg carcass weight and measured for loin pH at 24 h, myoglobin, iron and zinc concentrations, isocitrate dehydrogenase activity and intramuscular fat. Loin meat was aged for 5 d before being re-sliced and overwrapped for color measurement over a 72 h simulated retail display. Meat redness (R630/R580) was measured after blooming and every 24 h across display using a Hunterlab spectrophotometer. Simple and partial correlation coefficients between initial and subsequent R630/R580 measures over the display were low (≤ 0.4). Accounting for key muscle traits influencing meat color such as pH24, myoglobin, iron or intramuscular fat concentration did not improve these correlations between bloomed meat color and subsequent meat color over retail display. Therefore bloomed meat color at the start of display is not a useful predictor of meat browning after 24 h of retail display. Alternatively, correlations between 24, 48, and 72 h R630/R580 were > 0.8, suggesting that meat color measured from 24 h of display can accurately predict subsequent retail meat browning.

Effect of Merino sheep age on consumer sensory scores, carcass and instrumental meat quality measurements

Slower growing Merino sheep often miss the lamb category and become yearlings. Yet, they may still produce meat of acceptable eating quality, thus opening the opportunity to develop high quality yearling products. Consumer sensory differences (tenderness, overall liking, juiciness, liking of flavour and liking of odour) of grilled wet-aged (5 days) steaks from the M. longissimus lumborum (LL) and M. semimembranosus (SM) derived from wether lamb (n = 185; average age 355 days) and wether yearling (n = 206; average age 685 days) Merinos were tested. Additionally, the age effect on carcass and instrumental meat quality traits was analysed. Lambs were born in 2009 and 2010 at two research sites (Kirby, Katanning), and yearlings were born in 2009 at five research sites (Kirby, Cowra, Rutherglen, Struan, Katanning). On average within each muscle, yearlings had lower scores for all sensory attributes (P &lt; 0.01) compared to lambs. Lambs versus yearlings born in the same year and reared at the same research site had greater sensory differences within the SM (P &lt; 0.01), up to 10.0 eating quality scores more for tenderness. In contrast, the LL samples had almost no significant differences between the two age groups. A portion of the differences in overall liking and liking of flavour scores was explained by intramuscular fat. Yearlings were slightly heavier (P &lt; 0.01) but leaner (P &lt; 0.01), compared to lambs, and yearling meat colour was darker (P &lt; 0.01). While the results generally supported the better eating quality of lamb, they demonstrated a very acceptable yearling LL eating quality, and showed the smaller impact of age on the LL muscle in Merinos. Hence, the development of a high quality yearling product for the LL muscle is possible.

Feed deprivation in Merino and Terminal sired lambs: (2) the metabolic response under pre-slaughter conditions and impact on meat quality and carcass yield

Under current Australian industry pre-slaughter guidelines, lambs may be off feed for up to 48 h before slaughter. The purpose of this study was to examine what proportion of circulating metabolites at slaughter are due to stress and feed deprivation and if this response differs between Merino and Terminal genotypes. In addition the effect of feed deprivation on carcass weight and meat quality was examined. Jugular blood samples were collected from 88 Merino and Terminal sired lambs at rest and at slaughter following 24, 36 and 48 h of feed deprivation and plasma analysed for glucose, lactate, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHOB). From the same carcasses hot carcass weight (HCWT) were measured as well as a suite of meat quality traits measured such as M. longissimus lumborum (loin) and M. semitendinosus pH at 24 h postmortem. Loin samples were also analysed for intramuscular fat content and Warner-Bratzer Shear Force. Merino sired lambs had a higher NEFA response compared to Terminal sired lambs at slaughter after 24, 36 and 48 h of feed deprivation, with NEFA levels up to 35% higher than previously reported in the same animals at rest in animal house conditions, whereas BHOB response to feed deprivation was not affected by sire type (P&gt;0.05) and similar to previously reported at rest. In addition to the metabolic effects, increasing feed deprivation from 36 h was associated with a 3% reduction in HCWT and dressing percentage as well as causing increased ultimate pH in the M. semitendinosus in Merino sired lambs. Findings from this study demonstrate that Merino and Terminal sired lambs differ in their metabolic response to feed deprivation under commercial slaughter conditions. In addition, commercial feed deprivation appears to have a negative effect on ultimate pH and carcass weight and warrants further investigation.

Association between Loin Ultimate pH and Plasma Indicators of Pre-Slaughter Stressors in Australian Lamb

The purpose of this study was to test if associations exist between plasma indicators of acute and chronic stress and lamb ultimate pH. Blood was collected at exsanguination from 2,877 lambs from the Meat and Livestock Australia Genetic Research flock with a suite of indicators analyzed. Ultimate pH was measured in the loin (M. longissimus lumborum) at 24 h post-slaughter. There was a positive association (P < 0.05) between ultimate pH and plasma glucose and lactate concentrations, which indicates that opportunities exist to reduce variation in ultimate pH by reducing stress in the pre-slaughter period. These effects were small by comparison to production factors, however further understanding of how to best manage lambs in the pre-slaughter period is required to minimize stress and maximize lamb wellbeing and meat quality.

Genetic correlations between wool traits and meat quality traits in Merino sheep

Genetic correlations between 29 wool production and quality traits and 25 meat quality and nutritional value traits were estimated for Merino sheep from an Information Nucleus (IN). Genetic correlations among the meat quality and nutritional value traits are also reported. The IN comprised 8 flocks linked genetically and managed across a range of sheep production environments in Australia. The wool traits included over 5,000 yearling and 3,700 adult records for fleece weight, fiber diameter, staple length, staple strength, fiber diameter variation, scoured wool color, and visual scores for breech and body wrinkle. The meat quality traits were measured on samples from the and included over 1,200 records from progeny of over 170 sires for intramuscular fat (IMF), shear force of meat aged for 5 d (SF5), 24 h postmortem pH (pHLL; also measured in the , pHST), fresh and retail meat color and meat nutritional value traits such as iron and zinc levels, and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. Estimated heritabilities for IMF, SF5, pHLL, pHST, retail meat color lightness (), myoglobin, iron, zinc and across the range of long-chain fatty acids were 0.58 ± 0.11, 0.10 ± 0.09, 0.15 ± 0.07, 0.20 ± 0.10, 0.59 ± 0.15, 0.31 ± 0.09, 0.20 ± 0.09, 0.11 ± 0.09, and range of 0.00 (eicosapentaenoic, docosapentaenoic, and arachidonic acids) to 0.14 ± 0.07 (linoleic acid), respectively. The genetic correlations between the wool production and meat quality traits were low to negligible and indicate that wool breeding programs will have little or no effect on meat quality. There were moderately favorable genetic correlations between important yearling wool production traits and the omega-3 fatty acids that were reduced for corresponding adult wool production traits, but these correlations are unlikely to be important in wool/meat breeding programs because they have high SE, and the omega-3 traits have little or no genetic variance. Significant genetic correlations among the meat quality traits included IMF with SF5 (-0.76 ± 0.24), fresh meat color * (0.50 ± 0.18), and zinc (0.41 ± 0.19). Selection to increase IMF will improve meat tenderness and color which may address some of the issues with Merino meat quality. These estimated parameters allow Merino breeders to combine wool and meat objectives without compromising meat quality.

Meat quality attributes of Agile Wallabies

Meat quality traits of Agile Wallaby (Macropus agilis) M. longissimus (loin) and M. semimembranosus (topside) were investigated. Both muscles exhibited a relatively high pH (>5.7) and dark colour (L*-, a*-, and b*-values). Aging the loins from 2 to 21days p.m. had a significant effect on shear force. However, the results regarding shear force, myofibrillar fragmentation index (MFI) and degradation of desmin and troponin-T suggested that the aging response largely occurred within 2days p.m. Suspension of carcasses from one leg resulted in a side effect on shear force of the loin at 2 and 7days p.m., but not on sarcomere length or MFI. Topsides from the free hanging leg exhibited lower shear force values (33 vs 42N) and greater sarcomere lengths (2.51 vs 1.84μM). Tenderness, juiciness, flavour and overall liking were higher for loins than topsides. Sensory scores for the loin and topside were slightly lower and similar, respectively, to those reported for lamb.

Selection for intramuscular fat and lean meat yield will improve the bloomed colour of Australian lamb loin meat

The colour of bloomed m. longissimus was measured 24h post slaughter for 8165 lamb carcasses produced over 5years across 8 sites in Australia. Intramuscular fat across a 2 to 8% range and shortloin fat weight were positively associated with meat lightness (L*), redness (a*), yellowness (b*), hue and chroma (P<0.01). Shortloin muscle weight was negatively associated with these meat colour parameters (P<0.01), although this was largely accounted for by correlated changes in intramuscular fat (P<0.01). The effect of sire breeding values for lamb weight, shortloin muscle depth and fat depth on loin L*, a*, b*, hue and chroma were small and varied between lambs of different sire type, dam breed and sex. Thus selection for lean meat yield will have neutral or positive effects on meat colour, while selection for increased intramuscular fat will make the bloomed colour of lamb meat lighter and redder.

Optimum number of technical replicates for the measurement of compression of lamb meat

Up to six (average 4.63) replicate compression values were collected on cooked m. semimembranosus of lambs that had been raised at six sites across southern Australia (n=1817). Measurements on each sample were made with one of two Lloyd Texture analyser machines, with each machine having a 0.63 cm diameter plunger. Based on a log normal model with common variance on the log scale for within sample replicate results, estimates of the within sample variability of compression values were obtained, resulting in a quality control procedure for compression testing based on the coefficient of variation.

Intramuscular fat in lamb muscle and the impact of selection for improved carcass lean meat yield

Intramuscular fat percentage (IMF%) has been shown to have a positive influence on the eating quality of red meat. Selection of Australian lambs for increased lean tissue and reduced carcass fatness using Australian Sheep Breeding Values has been shown to decrease IMF% of the Muscularis longissimus lumborum. The impact this selection has on the IMF% of other muscle depots is unknown. This study examined IMF% in five different muscles from 400 lambs (M. longissimus lumborum, Muscularis semimembranosus, Muscularis semitendinosus, Muscularis supraspinatus, Muscularis infraspinatus). The sires of these lambs had a broad range in carcass breeding values for post-weaning weight, eye muscle depth and fat depth over the 12th rib (c-site fat depth). Results showed IMF% to be highest in the M. supraspinatus (4.87 ± 0.1, P<0.01) and lowest in the M. semimembranosus (3.58 ± 0.1, P<0.01). Hot carcass weight was positively associated with IMF% of all muscles. Selection for decreasing c-site fat depth reduced IMF% in the M. longissimus lumborum, M. semimembranosus and M. semitendinosus. Higher breeding values for post-weaning weight and eye muscle depth increased and decreased IMF%, respectively, but only in the lambs born as multiples and raised as singles. For each per cent increase in lean meat yield percentage (LMY%), there was a reduction in IMF% of 0.16 in all five muscles examined. Given the drive within the lamb industry to improve LMY%, our results indicate the importance of continued monitoring of IMF% throughout the different carcass regions, given its importance for eating quality.

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.