Effect of different gas stunning methods on Manchega suckling lamb meat packed under different modified atmospheres.

Forty-nine Manchega breed male suckling lambs were used in this experiment. The effect of CO(2) concentration and exposure time at stunning [80% CO(2) for 90 s (G1); 90% CO(2) for 90 s (G2); 90% CO(2) for 60 s (G3); 80% CO(2) for 60 s (G4)] plus an electrically stunned control group (G5) was assessed for pH, colour (L(*), a(*), b(*), C(*) and h(*)), water holding capacity (WHC), drip loss (DL), cooking loss (CL) and shear force (SF) in samples packed under two different types of modified atmospheres (MA: MA A: 70%O(2)+30%CO(2); MA B: 69.3%N(2)+30%CO(2)+0.7%CO) at 7, 14 and 21 d post-packaging. The lowest pH was found in G4 and in G5. The highest WHC and the lowest CL were found in G2 and G3 groups (P<0.05). Modified atmospheres did not affect on pH, WHC, CL and DL, although a significant effect (P<0.001) on colour was found at all the analysis times. Both the type of stunning and the modified atmosphere affected SF values.

Physiological responses of Manchega suckling lambs: Effect of stunning with different CO(2) concentrations and exposure times.

Four groups of Manchega breed suckling lambs, stunned with different CO(2) concentrations and exposure times (G1: 80% CO(2) 90s; G2: 90% CO(2) 90s; G3: 90% CO(2) 60s; G4: 80% CO(2) 60s) plus an electrically stunned control group (G5), were used to determine (1) the physiological responses (hormonal, haematological and biochemical blood parameters) of animals after stunning and (2) the stunning effectiveness in each group. No significant differences were found among groups for hormonal levels. Within haematological parameters, significant differences among groups were only found for haemoglobin (P<0.05) and leucocytes (P<0.01), with lowest values in both groups stunned with 90% CO(2). There were significant differences between groups (P<0.01) for urea and total protein, creatinine and LDH (P<0.05; lowest and highest, respectively, for G1) and for sodium (P<0.001; lowest in G3). Stunning effectiveness was highest in G5, G3 and G1 groups and lowest in G2 and G4 (100%, 90%, 89%, 50% and 43%, respectively). According to discriminant analysis, sodium, leucocytes and creatinine marked the differences among stunning groups.

Effects of stunning with different carbon dioxide concentrations and exposure times on suckling lamb meat quality.

Forty-nine Manchega breed male suckling lambs were used to determine the effect of different stunning methods (using two different CO2 concentrations and exposure times) on lamb meat quality. The lambs were allocated to five stunning treatments including four CO2 treatments [80% CO2 for 90s (G1); 90% CO2 for 90s (G2); 90% CO2 for 60s (G3); 80% CO2 for 60s (G4)] and an electrically stunned control group (G5). The gas-stunning treatments did not cause neither haematomas nor blood splash in the carcasses. Meat quality was evaluated by testing pH, colour (L(∗), a(∗), b(∗), chroma, hue values), water holding capacity (WHC), cooking loss (CL), shear force (SF), drip loss (DL) and total aerobic bacteria. Statistical differences in pH at 24h post-mortem, colour, WHC and CL were not found among groups. After 7 days post-mortem, there were statistical differences among groups in pH (highest in G4 and G5) and in DL (highest in G1). There were differences in SF due to stunning method evident after 72h and 7 days ageing. The statistical differences (P<0.01) among groups on total aerobic bacteria at 24h (lower and higher values in G2 and G5, respectively) disappeared at 7 days post-mortem. As G2 as G3, could be recommended to stunning suckling lambs since a highest stability with ageing time on meat quality was found using 90% CO2.

CO(2) stunning procedure on Manchego light lambs: Effect on meat quality.

This study examined the effect of different gas stunning methods (concentration of CO(2)/time of exposure (G1: 80%90s; G2: 90%90s; G3: 90%60s; G4: 80%60s) on the initial meat quality of Manchego breed light lambs (25kg live weight) and at 7days post-mortem, assessed by pH, colour coordinates, water holding capacity (WHC), cooking loss (CL), drip loss (DL) shear force (SF) and lipid oxidation. An electrically stunned control group (G5) was used. Stunning method had a significant effect on pH values (P<0.001) as well as on pH decline (P<0.01). The lowest pH was found at 24h post-slaughter in G1 and the highest one on G5. The greatest drop in pH (pH(0)-pH(24)) was found in G1 and G5 while the smallest in G3. In general values of colour coordinates, WHC and DL were similar in all groups. Stunning method affected CL (P<0.001) at 7 days post-slaughter, with the lowest values being found in G1. Significant differences among groups were found (P<0.05) in SF values at both post-mortem times, with less tender meat in groups stunned with 80% CO(2), especially in G1. A significant effect (P<0.001) due to the type of stunning was found at 24h on lipid oxidation, with the highest value in G5. After ageing this parameter was lowest (P<0.05) in G1 and G4.

Microbial quality and lipid oxidation of Manchega breed suckling lamb meat: Effect of stunning method and modified atmosphere packaging.

The effect of CO(2) concentration and exposure time at stunning [80% CO(2) for 90s (G1); 90% CO(2) for 90s (G2); 90% CO(2) for 60s (G3); 80% CO(2) for 60s (G4)] plus an electrically stunned control group (G5) was assessed for lipid oxidation (LO) and microbial levels, [total viable counts, lactic acid bacteria, Enterobacteriaceae and Pseudomonas spp.] in Manchega breed suckling lamb meat at 24h and 7days post-mortem. Differences in LO were found at 7days post-mortem (P<0.05) with the highest value for G4. In general, values of all microorganisms studied were higher in G5. In addition the effects of these stunning methods (TS) on both LO and microbial counts were assessed in samples packed under two different types of modified atmospheres (MA: MA-A: 70% O(2)+30% CO(2); MA-B: 69.3% N(2)+30% CO(2)+0.7% CO) at 7, 14 and 21days post-packaging. Both factors (TS and MA), significantly affected LO, which was highest in the samples from the MA-A/G4 group. In general there were no significant differences in microbial quality between modified atmospheres. However, the type of stunning affected microbial count (P<0.001) at all analysis times. In general, G4 and G5 showed the highest level in all microorganisms assessed, while the rest of the gas-stunning groups showed more stability with ageing.

Effect of stunning systems on meat quality of Manchego suckling lamb packed under modified atmospheres.

The effects of the type of stunning (TS) [electrically vs. gas] and packing in modified atmospheres (MA) [MA-A: 30% CO(2)/70% O(2); MA-B: 30% CO(2)/69.3% N(2)/0.7% CO; MA-C: 40% CO(2)/60% N(2)] on meat quality (pH), drip losses (DL), water holding capacity (WHC), shear force (SF) and instrumental colour (L(∗), and C(∗)chroma) of suckling lamb of the Spanish Manchego breed at 7, 14 and 21d post-packing was studied. Acceptance of meat samples (on the basis of colour and odour) was determined. In general neither the TS nor the MA affected the pH values. Meat from the gas stunned lambs had the lowest DL (P<0.001 at 14d post-packing), but lower WHC (more water expelled; P<0.01 at 14 and 21d post-packing), was more tender (P<0.01) and had higher L(∗) (P<0.001 at 14d post-packing) and C(∗) values (P<0.001) than the electrically stunned group. Similar values of WHC and SF were observed for all MA types but the use of CO in the packs (MA-B) caused less DL, gave the highest C(∗) values, acceptability and colour stability with time of storage.

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 24h and 7 days post-mortem. Lambs were electrically stunned (ESL; n=10), using CO(2) (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 24h 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.

Lipid oxidation in lamb meat: Effect of the weight, handling previous slaughter and modified atmospheres.

This study examined the effect of pre-slaughter handling (electrical, gas (CO(2)) or non-stunning) on lipid oxidation (as thiobarbituric acid reactive substances, TBARS; in the unit of mg malondialdehyde/kg(-1) of meat) of Spanish Manchega breed lamb meat, at 24h and at 7 days post-mortem. Lambs were slaughtered at two different weights (light (L), 25kg, vs. suckling (S), 12.8kg). In general gas-stunned lambs had lower lipid oxidation (P<0.001), and it was higher (P<0.001) in light lambs compared to suckling lambs. In both groups (S and L), malondialdehyde level increased with time (P<0.001), although this increase was lower (P<0.05) in gas-stunned suckling lambs. In addition, we evaluated the effect of stunning methods (TS: electrical vs. gas) and the weight (L vs. S) on lipid oxidation values in samples packed in different types of modified atmosphere (MA: A: 70%O(2)+30%CO(2); B: 69.3%N(2)+30%CO(2)+0.7%CO; C: 60%N(2)+40%CO(2)) at 7, 14 and 21 days post-packing. Values were higher in samples with MA-type A and lower in B and C types (P<0.05). A significant interaction (P<0.001) weight×TS was observed and the lowest rates of TBARS were found in the samples of light lambs stunned with gas and packed under anaerobic conditions (MA-B and C).