Effect of electrical stunning on meat quality of lamb

The effects of stunning on both initial and up to 2 weeks post mortem storage meat quality of Spanish Manchega breed lamb were studied. Twenty-four lambs were distributed into two groups. The first group (US; n =12) were slaughtered without previous stunning. In the second group (ES; n =12) animals were electrically stunned. Meat quality was assessed by examining pH, colour as L*, a*, b* values, water holding capacity (WHC) and shear force (SF). Stunning did not affect any parameter studied in the first 24 h post mortem. There were increasing differences between groups in pH (P<0.001) from 5 days onwards. In general stunning did not have an effect on WHC, SF and colour parameters. Ageing of meat affected SF in the ES group but not in the US one; however, there were no significant differences between treatments at any of the ageing times.     

Eating quality of lamb meat: effects of breed, sex, degree of maturity and nutritional management

The eating quality of lamb meat of three indigenous Greek dairy breeds of sheep, reared under different nutritional management conditions, was assessed by Taste Panel Tests (TPT). Lean samples from the leg joints of 69 lamb carcasses of the Boutsko (B), Serres (S) and Karagouniko (K) breed were used. For the first TPT, 24 lambs (four males and four females of each breed) were reared in individual pens on a concentrate ration fed ad libitum. For the second TPT, 27 individual penned male lambs were fed on Lucerne hay ad libitum and on three different levels of concentrate: High (H), Medium, (M) and Low (L). For the third TPT, 18 male lambs were used; initially the groups were fed indoors for 63 days on three different levels of concentrate (H, M and L) together with ad libitum Lucerne hay, and subsequently finished on irrigated, sown pasture. For TPT 1, leg joints were obtained from lambs that had been slaughtered at 30, 45, 60 or 90% of mature weight (PMW) for each breed. For TPT 2, lambs were slaughtered at 23, 28 or 33 kg target slaughter live weights (TSLW), common for all breeds. For TPT 3, lambs were slaughtered at 48 or 55% of PMW for each breed. Panellists assessed warm, roasted lean samples of leg joints and rated Flavour, Juiciness, Tenderness and Overall Acceptability. In TPT 1, degree of maturity significantly affected Flavour, Tenderness and Overall Acceptability whereas sex affected only Flavour. In TPT 2, breed and concentrate level significantly affected the quality characteristics, but concentrate level had no significant effect in TPT 3. Effects associated with slaughter weight were significant for most characteristics in all TPT, with decreasing acceptability for older/heavier lambs. Significant interactions were found between breed and the other factors in TPT 2 and TPT 3 for most quality characteristics. Results from these studies suggest changing traditional production systems may enhance the eating quality of lamb meat.     

Effect of lamb age and retail packaging types on the quality of long-term chilled lamb loins

The objective of this study was to determine the impact of lamb age and packaging types on meat quality. Paired loins (M. longissimus dorsi) were obtained from 36 carcasses that included 4-month-old (New season; NS) and 11-month-old lambs (Old season; OS). The loins were vacuum-stored for eight weeks at − 1.5 °C. After storage, the loins were cut into subsamples and were randomly assigned to either high-oxygen modified atmosphere packaging (HiOx-MAP) or PVC-overwrapping for further display for 8 days. No differences between the age classes in shear force and drip loss were found (P > 0.05). OS loins had significantly higher myoglobin and redness compared with NS loins. HiOx-MAP initially induced a more intense red colour compared with PVC (P < 0.05), but resulted in severe discolouration at the end of display regardless of the age class. This observation suggests that the retail packaging type is the dominant factor over the age on lamb colour stability.     

Comparison of different dietary magnesium supplements on pork quality

Forty-eight crossbred (Large White×Landrace) boars were used to compare the effect of dietary magnesium aspartate (MgAsp), magnesium sulphate (MgSO(4)) and magnesium chloride (MgCl(2)) on muscle glycogenolysis and pork quality. The pigs were fed finisher feed supplemented with either MgAsp, MgSO(4) and MgCl(2) for 5 days prior to slaughter. At the abattoir, all pigs received 15 electric shocks from an electric goad 5min prior to slaughter. Pigs fed the diet supplemented with MgSO(4) had the highest plasma Mg concentrations at slaughter in comparison with pigs fed the MgAsp and MgCl(2) supplemented diets. There were no differences in plasma adrenaline and noradrenaline concentrations at slaughter between the different diets. Pigs fed the Mg diets had higher muscle glycogen concentrations in the Longissimus thoracis (LT) muscle at 5min and at 40min (except MgCl(2)) post-slaughter compared to pigs fed the control diet. Also pigs fed the Mg diets had lower muscle lactic acid concentrations in the LT at 5min post-slaughter and lower drip loss at 24hr post-slaughter compared to pigs fed the control diet. These results indicate that cheaper magnesium sources, MgSO(4) and MgCl(2), are as efficacious as MgAsp in reducing drip loss and improving pork quality.     

Predicting the composition of lamb carcases using alternative fat and muscle depth measures

Hot carcase weight (HCW) and the GR tissue depth (total tissue depth over the 12th rib, 110 mm from the midline) were measured on 312 crossbred (Poll Dorset × Merino) lambs with a mean live weight of 47 kg. At a position 30 mm distal to the lumbar-sacral junction, the depth (RMD) of the rump muscles was measured along with subcutaneous fat depth overlaying the m. gluteus medius (RFD). The subcutaneous fat depth over the m. longissimus (loin) at the 12th rib was measured (Fat C), as was the depth and width of the loin cross section (EMD and EMW, respectively). The right side of each carcase was scanned by a dual energy X-ray bone densitometer and fat and lean weight determined and the percentage of lean and fat content in the carcases calculated. HCW alone accounted for 26% of the variation in percentage lean content (LC), with GR measurement being the single best predictor of LC (R² = 48.1; r.s.d. = 1.89). RFD provided a less accurate and precise estimate of LC (R² = 37.3; r.s.d. = 2.07) than either GR or Fat C (R² = 46.5; r.s.d. = 1.92). Inclusion of HCW with either GR or Fat C provided a small improvement in the amount of variation in LC which could be explained. The measurement of breeding animals by ultrasound includes the terms weight, Fat C and EMD. These predictors when combined explained 49% of the variation in LC whereas by comparison measures of weight, RFD and RMD only explained 42% of the variation in LC. The current method of measuring fat depth over the 12th/13th rib is practical and measurement over the rump does not present an advantage based on the results of this study.     

Meat quality of lamb: Pre-slaughter fattening on cultivated or mountain range pastures

Many consumers perceive lamb meat from mountain pastures to be of superior quality, a quality that may be altered if lambs are kept for a longer period on cultivated pastures before slaughtering. The objective of this experiment was to compare sensory profile and fatty acid composition in meat from lambs slaughtered directly from unimproved mountain pastures with meat from lambs raised on unimproved mountain pastures and fattened on biodiverse cultivated pastures for 26, 39 and 42 days before slaughtering. The experiment was conducted at two different locations in Norway in 2006 and 2007, with a total of 124 Norwegian Crossbred Sheep lambs. Loin samples of M. Longissimus dorsi from lambs above a body weight of 40 kg were selected and analysed for sensory attributes. Fatty acid composition was determined in the subcutaneous fat over the Longissimus dorsi. Small but significant differences were found in hardness, tenderness, fattiness, metallic and rancid flavour, and in polyunsaturated fatty acids. This indicates that to a small extent pre-slaughter fattening on cultivated pastures alters meat characteristics.     

Tenderness of pre- and post rigor lamb longissimus muscle

Lamb longissimus muscle (n=6) sections were cooked at different times post mortem (prerigor, at rigor, 1dayp.m., and 7 days p.m.) using two cooking methods. Using a boiling waterbath, samples were either cooked to a core temperature of 70 °C or boiled for 3h. The latter method was meant to reflect the traditional cooking method employed in countries where preparation of prerigor meat is practiced. The time postmortem at which the meat was prepared had a large effect on the tenderness (shear force) of the meat (P<0.01). Cooking prerigor and at rigor meat to 70 °C resulted in higher shear force values than their post rigor counterparts at 1 and 7 days p.m. (9.4 and 9.6 vs. 7.2 and 3.7 kg, respectively). The differences in tenderness between the treatment groups could be largely explained by a difference in contraction status of the meat after cooking and the effect of ageing on tenderness. Cooking pre and at rigor meat resulted in severe muscle contraction as evidenced by the differences in sarcomere length of the cooked samples. Mean sarcomere lengths in the pre and at rigor samples ranged from 1.05 to 1.20 μm. The mean sarcomere length in the post rigor samples was 1.44 μm. Cooking for 3 h at 100 °C did improve the tenderness of pre and at rigor prepared meat as compared to cooking to 70 °C, but not to the extent that ageing did. It is concluded that additional intervention methods are needed to improve the tenderness of prerigor cooked meat.     

Effects of cooling temperature and hot carcass weight on the quality of lamb

The effects of cooling temperature (CT) (0–2, 2–4, or 4–6 °C) and hot carcass weight (HCW) (either 10.5 or 12.0 kg) on weight loss (WL) and meat quality were evaluated in 60 lamb carcasses of Rasa Aragonesa breed. Carcasses were exposed to CT throughout 90 h. WL was assessed at 18, 42, 66, and 90 h post-slaughter. pH, colour, instrumental measurement of texture, oxidation, and sensory parameters were evaluated in longissimus thoracis et lumborum aged for 96 h following standard methods. Sensory test involved a trained test panel. No significant interactive effects among the parameters evaluated were detected in the study. The lower the CT, the higher the WL after 90 h in storage (0.25% lost each 2 °C decrease), the higher final pH, and the lower lightness, the higher hue and chroma of the meat. Toughness was higher in meat cooled at 2–4 °C than in meat cooled at temperatures above or below this range. Neither oxidation nor sensory variables were affected by CT. Regarding on HCW, light carcasses exhibited higher WL (2.39% versus 2.04% after 90 h of cooling), higher final pH, and lower levels of oxidation than did heavier carcasses. Neither colour nor instrumental measurement of texture was affected by HCW. Lamb and fat odour and metallic and acid flavour intensities were significantly greater in the heavier carcasses, although it did not affect overall acceptability. Both CT and HCW should be considered as main effects on lamb quality, especially CT.     

Prediction of lamb carcass composition and meat quality using combinations of post-mortem measurements

Various post-mortem measurements (carcass weights, conformation and fatness classes, external carcass dimensions, eye muscle dimensions, subcutaneous fat depth, pH and temperature) were recorded on 197 Texel (TEX) and 200 Scottish Blackface (SBF) lamb carcasses. The potential use of these measurements to predict carcass composition and key meat quality traits was investigated, to enable categorisation of carcasses in the abattoir and/or for use in genetic improvement programmes. By combining different measurements, accurate predictions of dissected carcass muscle weight (adjusted R² 0.93 in TEX, 0.88 in SBF) and fat weight (adjusted R² 0.84 in TEX, 0.87 in SBF) were achieved, and moderate predictions of intra-muscular fat (adjusted R² 0.56 in TEX, 0.48 in SBF), whilst shear force was predicted with low to moderate accuracy (adjusted R² < 0.33 across breeds and cuts). Sex, eye muscle dimensions and subcutaneous fat depth improved predictions of carcass composition and intra-muscular fat, whilst pH or temperature provided little additional benefit for these traits, but increased prediction accuracies for shear force. These results could contribute to the development of automated carcass grading systems or help inform breeding decisions.     

Effect of freezing method and frozen storage duration on instrumental quality of lamb throughout display

This study evaluated the effect of freezing method (FM) (air blast freezer, freezing tunnel, or nitrogen chamber) and frozen storage duration (FSD) (1, 3, or 6 months) on the instrumental measurements of quality of thawed lamb, aged for a total of 72 h, throughout a 10-d display period, compared to the quality of fresh meat. pH, colour, lipid oxidation, thawing, and cooking losses in Longissimus thoracis and lumborum muscle, were determined following standard methods. FM affected yellowness, FSD redness and thawing losses, and both affected oxidation (increased as freezing rate decreased and/or as storage duration increased). When compared with fresh meat, the main differences appeared on oxidation (where a significant interaction between treatment (3FM × 3FSD + fresh meat) with display duration was detected), and on total losses (thaw + cook losses). Oxidation was lower in fresh meat, but values were not significantly different from those stored frozen for 1 month. Fresh meat had smaller total losses than did thawed meat, but losses were not significantly different from meat frozen in the freezing tunnel and stored frozen for 1 month. Display duration had a greater effect on instrumental quality parameters than did FM or FSD. pH, b*, and oxidation increased, and L* and a* decreased with an increase in the number of days on display. In conclusion, neither freezing method nor frozen storage up to 6 months influenced extensively the properties of lamb when instrumental measurements of quality were measured in meat that had been displayed for 1 d after thawing. The small deterioration shown in this study should not give consumers concerns about frozen meat.     

The effects of the myostatin g+6723G>A mutation on carcass and meat quality of lamb

This study evaluated the effects of the myostatin g + 6723G > A mutation on carcass and meat quality traits of lamb (AA: n = 5; AG: n = 8; GG: n = 9). Dressing percentage was positively affected by the mutation with homozygotes for the mutation having the highest yield. Regarding carcass composition, there was a significant increase in the proportional weights of the loin and hindquarter muscles. Objective meat quality traits of the M. longissimus lumborum (LL) and M. semimembranosus (SM) were not significantly affected. For the SM, toughness (shear force and compression) tended to be lowest for homozygotes for the mutation. The myostatin g + 6723G > A mutation did not affect sensory meat quality traits of grilled steaks for the LL, but resulted in a significant improvement in eating quality for the SM. Given the number of animals in this study, the robustness of the outcome of this study with regard to the effects on meat quality and its causes requires further investigation.     

Use of generalized Procrustes analysis (GPA) to test the effects of sex and carcass weight on sensory quality evaluations of Terrincho lamb meat

Generalized Procrustes analysis (GPA) was used to test the sensory attributes of Terrincho lamb meat, a product with Protected Designation of Origin (PDO) labelling. Effects of sex and carcass weight on the following sensory attributes: toughness, juiciness, flavour intensity, odour intensity, stringiness, and level of sweetness were tested. Tests were performed on 28 females and 29 males placed within three classes of carcass weight, 3 to 9 kg. Meat sensory quality was evaluated, within five sessions, by a trained taste panel. Meat was cooked in a conventional oven, cut into pieces, and delivered to the panel for evaluation. Data were analyzed using a GPA to minimize differences between assessors. Two factors explained 72.76% of the total variability. The panel did not clearly detect sex effects, yet could differentiate meat by carcass weight as heavier animals were toughest and had more intense odour and flavour, whilst light animals were most succulent.     

Aspects of quality related to the consumption and production of lamb meat. Consumers versus producers

The purpose of this study was to identify and compare the different evaluations made by the agents at either end of the lamb meat chain, i.e. producers and consumers, in relation to the parameters that consumers use when purchasing lamb meat and the factors that affect the production of quality lamb meat. In addition, consumer segments that can be targeted for action by the different agents in the chain were examined. The study was carried out in Aragón, a region in north east Spain that is a producer and consumer of lamb meat. 371 surveys were carried out on purchasers of lamb meat and 49 surveys on sheep farmers. Bivariant analyses and a cluster analysis were performed. The results suggest that there are certain congruencies and divergences between producers and consumers. Also, a segment of consumers for whom the hygiene and sanitary conditions on the farm, animal welfare and the environment are of great importance were found.     

Acceptability of lamb meat from different producing systems and ageing time to German, Spanish and British consumers

In the present study German (DE), Spanish (ES) and British (UK) consumers' acceptance of lamb from their own country compared to lamb from Uruguay (UY) was evaluated. Two-hundred consumers in each country evaluated tenderness, flavour and overall acceptability of four types of lamb, two from UY (light and heavy lambs aged 20 d) and 2 local (with two ageing times, 7 and 20 d). In each country 1.5cm-thick slices of lamb were evaluated by previously selected consumers in controlled conditions. DE and UK consumers showed significantly (P<0.05) different acceptability scores between samples, the lamb from heavier animals and aged 20 d being the most appreciated. On the other hand the majority of the ES consumers significantly (P<0.05) preferred the meat from lighter lambs. Production systems, cultural aspects and consumption habits seem to affect the acceptability of the lamb to the consumers.     

Effect of dietary oregano oil supplementation on lamb meat characteristics

The effect of dietary oregano essential oil supplementation on lamb meat characteristics was investigated. Eight male and eight female Chios lambs were divided into two equal groups. The first group was fed with the control diet consisting of concentrated feed and alfalfa hay, whereas the second group consumed the same diet, the only difference being that the concentrated feed was uniformly sprayed with oregano essential oil (1 ml/kg). Duration of the experimental period was two months.

No differences were observed after oregano essential oil supplementation in final body weight (kg), body weight gain (g) and carcass yield (%). Tenderness of longissimus thoracis muscle, expressed as sarcomere length and shear force value, was not influenced by the treatment, whereas pH and colour parameters (yellowness–redness) appeared to increase (P < 0.05). Moreover, results showed that dietary incorporation of oregano essential oil exerted strong antioxidant effects retarding lipid oxidation (MDA formation) in meat during refrigerated and long-term frozen storage (P < 0.001).     

Influence of lamb age and high-oxygen modified atmosphere packaging on protein polymerization of long-term aged lamb loins

The objective of this study was to determine the influence of lamb age and high-oxygen modified atmosphere (HiOx-MAP) on tenderness of loins during display. Loins from 36 carcasses of two different age groups [4-month-old (New season; NS) and 11-month-old lambs (Old season; OS)] were vacuum-packaged and stored for 8 weeks at −1.5 °C. After storage, the loins were cut into 6-cm thick chops, assigned to either HiOx-MAP or oxygen-permeable overwrap-PVC, and then displayed for 8 days at 3 °C. Initially, packaging methods did not influence shear force (P > 0.05). However, at the end of display, a significant increase in shear force and lipid oxidation was found in OS loins under HiOx-MAP. SDS–PAGE and Western blot results found a greater extent of cross-linked myosin products from OS loins in HiOx-MAP compared to NS loins. These results suggest that HiOx-MAP can adversely influence meat quality of fully-tenderized loins, and meat from older lamb may be more susceptible to an oxidizing environment of HiOx-MAP.     

Effect of dietary supplementation with either red wine extract or vitamin E on the volatile profile of lamb meat fed with omega-3 sources

The effect of dietary supplementation with either vitamin E (300 ppm) or a red wine extract rich in polyphenols (900 ppm) in an omega-3 enriched concentrate on the volatile fraction of lamb meat was assessed. The effect of refrigerated storage (0 and 6 days) under high-oxygen atmospheres (70% O₂/30% CO₂) was also studied. Extraction and analysis of the volatile compounds was carried out by headspace solid-phase microextraction (HS-SPME) and GC–MS, respectively. Vitamin E supplementation led to lower levels of lipo-oxidation compounds, such as 2-heptanone and 1-penten-3-ol. The red wine extract was less efficient against lipid oxidation than vitamin E but more efficient than the control (no added antioxidants). The levels of numerous lipid-derived compounds were found to be lower after 6 days of storage which could be due to further interactions with protein-related compounds.     

Evaluation of control over the microbiological contamination of carcasses in a lamb carcass dressing process operated with or without pasteurizing treatment

The aim of this study was to quantify the hygienic status of a lamb slaughterhouse by means of multivariate statistical analysis, to demonstrate how the microbiological data could be exploited to improve the lamb slaughter process by constructing control charts and to evaluate the potential effect of an intervention step such as steam application on the microbiological quality of lamb carcasses. Results showed that pelt removal and evisceration were hygienically uncontrolled. TVC and Enterobacteriaceae progressively increased from the stage ‘after pelt removal of hind and forelegs/before final pulling’ to the stage ‘after evisceration/before pluck removal’ thus indicating possible deposition of microorganisms during these operations. It seems that the processing stages of freshly produced carcasses were better distinguished by Enterobacteriaceae, with evisceration contributing mostly to the final Enterobacteriaceae counts. Application of steam during the lamb slaughter process reduced microbial counts without adverse effects on the organoleptic characteristics of the carcasses. Moreover, the construction of control charts showed that decontamination with steam contributed to the maintenance of an in control process compared to that before the application of steam, suggesting the potential use of steam as an intervention step during the lamb slaughter process.     

Effect of different stunning systems on meat quality of light lamb

The present study was proposed to compare the effect that different types of stunning (TS) had on the quality of refrigerated meat from light lambs of the Spanish Manchega breed at 24 h and 7 days post-mortem. Lambs were electrically stunned (ESL; n = 10), using CO₂ (GSL; n = 10) or slaughtered without previous stunning (USL; n = 10). Measurements on meat quality were carried out by evaluating pH, colour coordinates (L^*, a^*, b^*), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, no significant differences were found in any of the variables studied. However, at 7 days post-mortem, meat quality was affected by the different TS: pH, CL and DL were lower (P < 0.001) in the USL group and GSL obtained the lowest a^* (redness) and b^* (yellowness) values (P < 0.01) than in the other groups. Ageing of meat affected SF in the ESL group (P < 0.01), although there were no significant differences due to treatments at any of the ageing times.