CO2 stunning procedure on Manchego light lambs: Effect on meat quality

This study examined the effect of different gas stunning methods (concentration of CO₂/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 (25 kg live weight) and at 7 days 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 24 h post-slaughter in G1 and the highest one on G5. The greatest drop in pH (pH₀–pH₂₄) 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% CO₂, especially in G1. A significant effect (P < 0.001) due to the type of stunning was found at 24 h on lipid oxidation, with the highest value in G5. After ageing this parameter was lowest (P < 0.05) in G1 and G4.     

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 90 s (G1); 90% CO₂ for 90 s (G2); 90% CO₂ for 60 s (G3); 80% CO₂ for 60 s (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 24 h 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 72 h and 7 days ageing. The statistical differences (P < 0.01) among groups on total aerobic bacteria at 24 h (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.     

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 CO₂ concentration and exposure time at stunning [80% CO₂ for 90 s (G1); 90% CO₂ for 90 s (G2); 90% CO₂ for 60 s (G3); 80% CO₂ 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%O₂ + 30%CO₂; MA B: 69.3%N₂ + 30%CO₂ + 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.     

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

The effect of CO₂ concentration and exposure time at stunning [80% CO₂ for 90 s (G1); 90% CO₂ for 90 s (G2); 90% CO₂ for 60 s (G3); 80% CO₂ for 60 s (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 24 h and 7 days post-mortem. Differences in LO were found at 7 days post-mortem (P < 0.05) with the highest value for G4. In general, values of all microorganisms studied were higher in G5.     

Systems stunning with CO2 gas on Manchego light lambs: Physiologic responses and stunning effectiveness

Effect of four stunning treatments using different CO₂ concentrations and exposure times (G1: 80%90 s; G2: 90%90 s; G3: 90%60 s; G4: 80%60 s) on hormonal, haematological and biochemical parameters in Manchego breed light lambs and their stunning effectiveness (% animals correctly stunned) was studied. An electrically stunned control treatment (G5) was used. G1 showed the highest plasmatic hormonal, red cell distribution (RDW) and lactate levels. Haemoglobin, mean corpuscular volume (MCV), mean cell haemoglobin (HbCM), glucose, lactate deshydrogenase (LDH), sodium, potassium and creatine kinase (CK) were highest in G5. Stunning effectiveness was maximum (100%) in G3 and G5, only 50% in G1 and G2 and minimum (30%) in G4.     

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% CO₂/70% O₂; MA-B: 30% CO₂/69.3% N₂/0.7% CO; MA-C: 40% CO₂/60% N₂] 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 21 d 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 14 d post-packing), but lower WHC (more water expelled; P < 0.01 at 14 and 21 d post-packing), was more tender (P < 0.01) and had higher L^∗ (P < 0.001 at 14 d 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.     

Packaging-specific influence of chitosan on color stability and lipid oxidation in refrigerated ground beef

We examined the influence of chitosan on lipid oxidation and color stability of ground beef stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with chitosan (1%) or without chitosan (control) were packaged either in high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), vacuum (VP), or aerobic packaging (PVC) and stored at 1 °C. Chitosan increased (P < 0.05) redness of patties stored in PVC and CO, whereas it had no effect (P > 0.05) in HIOX. Chitosan patties demonstrated lower (P < 0.05) lipid oxidation than controls in all packaging. Control patties in PVC and HIOX exhibited greater (P < 0.05) lipid oxidation than those in VP and CO, whereas chitosan patties in different packaging systems were not different (P > 0.05) from each other. Our findings suggested that antioxidant effects of chitosan on ground beef are packaging-specific.     

Physico-mechanical properties of chitosan films with carvacrol and grape seed extract

The physico-mechanical properties of 3 films composed by carvacrol, grape seed extract (GSE) and chitosan in different proportions were studied. The films, prepared by solvent casting technique with the following compositions of the casting solutions in carvacrol, GSE and chitosan: film-1: 9.6 ppm–684 ppm–1.25% w/v, film-2: 60 ppm–400 ppm–1.2% w/v and film-3: 90 ppm–160 ppm–1.24% w/v and were compared to a control (1.25% w/v chitosan) film. Mechanical, structural, barrier and colour properties of the films were evaluated. Film-3 presented the lowest water vapour and carbon dioxide permeabilities (WVP and CO₂P) and tensile strength (TS) values and the highest oxygen permeability (O₂P), whereas film-1 presented the highest water content and the lowest crystallinity, CO₂P, TS and luminosity. These results suggest that in the range studied, carvacrol and GSE affect the film structure and its mechanical properties due to hydrophilic (GSE) and hydrophobic (carvacrol) compounds. This work will help the development of edible films, based on physico-mechanical properties, contributing to food preservation and shelf-life extension.     

CO(2) stunning may compromise swine welfare compared with electrical stunning

The effects of two different stunning methods on critical blood values in fattening pigs at a federal inspection slaughtering plant were monitored. A total of 658 pigs from the same genetic line and origin, were randomly assigned to 3 treatments: reference baseline levels (resting pigs; T1), stunning with CO₂ (T2) and stunned electrically (T3). Energetic profile, acid imbalance and blood gas levels, were monitored. Significant differences (p ? 0.05) between treatments for all variables were found, CO₂ stunned pigs showed hypercapnia, hypercalcemia, hyperglucemia, lactic acidemia, and an increase in haematocrit, coupled with reduced pH, _PO₂$P_{{\text{O}}_2}$, and Na; electrically stunned pigs had reduced blood pH, _PCO₂$P_{{\text{CO}}_2}$ and _PO₂$P_{{\text{O}}_2}$. The remaining indicators were increased in relation to the resting swine. Thus CO₂ stunning leads to a major imbalance because of mineral and acid base gaseous interchange, compared to electric stunning, thus possibly compromising animal welfare.     

Effects of high CO2 and low O2 atmospheres on the berry drop of ‘Kyoho’ grapes

To investigate the effects of low O₂ and high CO₂ atmospheres on the berry drop of ‘Kyoho’ grapes (Vitis vinifera X V. labrusca), changes of fruit detachment force (FDF) and berry abscission and enzyme activities in the abscission zone were examined during 60 days of storage in air (control), 4%O₂ + 9%CO₂ or 4%O₂ + 30%CO₂ at 0 °C and 95%relative humidity. There was a high negative correlation between FDF and berry drop. Cellulase activity increased over time and was closely correlated with berry abscission. Polygalacturonase (PG) activity rose markedly for the first 30 days and then remained relatively constant. Peroxidase (POD) activity dropped significantly for the first 15 days and subsequently rose sharply (P < 0.05). Cellulase, PG and POD activities were the lowest in fruits in 4%O₂ + 30%CO₂, followed by 4%O₂ + 9%CO₂ and air storage. Pectinesterase (PE) maintained a basal level of activity and there were no significant differences among three treatments (P < 0.05). Compared to air control, the combined effects of the lower level of O₂ and the higher level of CO₂ suppressed the activities of cellulase, PG and POD, maintained greater FDF, and reduced berry abscission during storage.     

Solubility, absorption and desorption of carbon dioxide in chicken breast fillets

The solubility for carbon dioxide (CO₂) in skinless chicken breast fillets was investigated. Henry's constant for chicken breast fillets was calculated to be 42.8 ± 3.7 Pa (mg kg^-1)^-1 at 275 K.In addition, the effects of soluble gas stabilization (SGS) time and waiting time before MA packaging on amount of solubilized CO₂ were investigated. Increasing SGS treatment time, significantly (P < 0.001) increased the amount of dissolved CO₂, while increasing waiting time significantly (P < 0.001) reduced the dissolved CO₂. Desorption of CO₂ showed to be a time consuming process, giving the industry enough time to repackage SGS treated products without loosing vast amounts of dissolved CO₂.     

Effect of exposure to light on physico-chemical quality attributes of sliced dry-cured Iberian ham under different packaging systems

Dry-cured Iberian ham slices were stored under vacuum and under two different atmospheres (N₂ = 70% N₂ + 30% CO₂; Ar = 70% Ar + 30% CO₂) and exposed to lightness or darkness. Physico-chemical, sensory and microbial analysis was carried out throughout 60 days storage. Vacuum samples showed the highest a*-value compared to N₂ and Ar after 30 (P < 0.05) and 60 days (P < 0.05). The influence of illumination during storage was evident after 60 days of storage, L* and a*-values being lower (P < 0.01) in hams exposed to light than those kept in darkness, which can be ascribed to the lower nitrosylmioglobin content in samples exposed to light after 60 days (P = 0.001). Ham slices stored in darkness showed the lowest TBARS values (P < 0.05) and hexanal content (P < 0.05) after 60 days. Slices of ham packed in vacuum showed lower TBARS values than N₂ and Ar batches (P = 0.001), these samples being perceived as more rancid (P < 0.05). The rest of the sensory attributes were not generally affected by gas mixture or illumination (P > 0.05).     

Chemical composition characteristics of the longissimus and semimembranosus muscles for pigs from New Zealand and Singapore

A range of composition characteristics of the longissimus (LL) and semimembranosus (SM) muscles were compared between pigs raised in intensive and extensive production systems in New Zealand (NZ), and pigs raised in an intensive system in Indonesia for supply to the Singapore market (n = 8/group). Ultimate pH was slightly higher for the Singaporean LL muscles (P < 0.05), while LL muscle of the NZ extensive group was redder (higher a^∗ values) and contained more fat (P < 0.05). Muscle iron levels were highest for the NZ extensive group and lowest for a lighter group within the Singapore pigs (P < 0.05). Differences in fatty acid concentrations, which were also measured in a sample of the belly cut, could largely be attributed to the effects of diet, with higher levels of alpha linolenic acid for the NZ extensive group (P < 0.05) due to linseed in the diet, and much higher levels of linoleic acid and the P:S ratio for the Singapore group (P < 0.05). Some statistically significant differences in amino acid concentrations were shown between muscles and groups, but they were not large. With respect to compounds with potential bioactive properties, coenzyme Q_10, and taurine levels were higher in pork from NZ pigs, and carnosine levels were highest for the NZ intensive group (P < 0.05). The LL muscle contained more coenzyme Q₁₀ and taurine, but less carnosine than the SM muscle (P < 0.001). It is concluded that some of these composition differences in the pork from the muscles and groups compared may be of commercial importance, but several are likely to have been due to dietary or weight differences.     

The Effect of Stunning Methods on Rigor Mortis and Texture Properties of Atlantic Salmon (Salmo Salar)

Shear force and rigor mortis were used to evaluate the post‐mortem changes of muscle texture in Atlantic salmon (Salmo salar). The fish were either stunned with carbon dioxide (CO₂), electricity, or percussion prior to slaughter. The pre‐mortem stress during CO₂ stunning resulted in an earlier onset and resolution of rigor mortis, and accelerated post‐mortem softening of the muscle tissue as compared to the other stunning methods. No significant differences, either in development of rigor mortis or shear force, were seen between fish that were stunned with electricity or by percussion. Consequently electricity can be used for stunning fish prior to slaughter.     

Effect of lutein,sesamol, ellagic acid and olive leaf extract on the quality and shelf-life stability of packaged raw minced beef patties

The effects of lutein (100 and 200 μg/g muscle), sesamol (250 and 500 μg/g muscle), ellagic acid (300 and 600 μg/g muscle) and olive leaf extract (100 and 200 μg/g muscle) on total viable counts (TVCs), lipid oxidation (thiobarbituric acid-reactive substances, TBARS), colour, oxymyoglobin oxidation, pH, water-holding capacity (WHC), sensorial properties of raw beef patties (M. longissimus thoracis et lumborum) stored in modified atmosphere packs (80% O₂:20% CO₂) (MAP) aerobically at 4 °C for up to 8 and 12 days, respectively, were examined. All the nutraceuticals reduced (P < 0.001) TVCs. The addition of sesamol, ellagic acid and olive leaf extract reduced (P < 0.001) TBARS in raw beef patties in both packaging systems. Sesamol addition to beef resulted in lower (P < 0.01) a* redness values and increased oxymyoglobin oxidation. Conversely, lutein and olive leaf extract reduced (P < 0.001) oxymyoglobin oxidation relative to the control. The graded addition of ellagic acid and olive leaf extract improved (P < 0.001) WHC.     

Modified atmosphere packaging and vacuum packaging for long period chilled storage of dry-cured Iberian ham

Dry-cured Iberian ham slices were stored under vacuum and under four different modified atmospheres (60/40 = 60%N₂ + 40%CO₂; 70/30 = 70%N₂ + 30%CO₂; 80/20 = 80%N₂ + 20%CO₂; argon = 70%argon + 30%CO₂) at 4 ± 1 °C during 120 days. Gas composition, moisture content, pH, colour, pigment content, and lipid stability were measured, as well as sensory and microbial analysis were carried out throughout storage. A loss of intensity of red colour (a^*-values) was observed during storage in ham slices (P < 0.05). Consistently, MbFe(II)NO content also decreased throughout storage (P > 0.05). Slices of ham packed in 40%CO₂ (60/40) and 30%CO₂ (70/30) showed lower a^*-values than the rest of the batches after 60 days (P < 0.05), though differences were not evident after 120 days (P > 0.05). TBARs values showed an upward trend during the storage of packaged slices (P < 0.05). Vacuum-packed slices showed the lowest TBARs values and those packed with 40%CO_2, the highest. Sensory attributes did not vary significantly (P > 0.05) throughout storage under refrigeration and packed either in vacuum or in modified atmospheres. No safety problems were detected in relation to the microbial quality in any case.     

Effect of modified atmosphere and vacuum packaging on some quality characteristics and the shelf-life of “morcilla”, a typical cooked blood sausage

The effect of modified atmosphere and vacuum packaging on the shelf-life of “morcilla”, a traditional cooked blood sausage, was investigated. A total of 99 “morcillas” were packaged under vacuum and in modified atmosphere using three different gas mixtures: 15:35:50/O₂:N₂:CO₂ (atmosphere 1), 60:40/N₂:CO₂ (atmosphere 2) and 40:60/N₂:CO₂ (atmosphere 3), and stored during 2, 4, 6 and 8 weeks at 4 °C. Shelf life evaluation was based on pH, water activity (a_w), colour (CIE L*, a*, b*, C* and h*), TBARS formation and microbial counts. The results indicated that, in general, storage time affected (P < 0.05) all parameters whereas no significant differences were observed (P > 0.05) among packaging conditions. Based on the microbial counts, the shelf-life of “morcilla” would be greater than 8 weeks for all packaging conditions. Samples packaged with high CO₂ concentrations (40:60/N₂:CO₂) showed the lowest values of TBARS at the end of storage.     

Color-stabilizing effect of lactate on ground beef is packaging-dependent

Previous research on lactate-induced color stability in ground beef did not address the potential influence of packaging. The objective of the present study was to examine the effects of lactate on the color stability of ground beef patties stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with either 2.5% potassium lactate or no lactate were packaged in vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), or aerobic packaging (PVC) and stored for 0, 2, or 4 days at 2 °C. Lactate-treated patties were darker (P < 0.05; lower L∗ values) than control patties. Surface redness (a∗ values) was greater (P < 0.05) for lactate patties than the controls when stored in PVC, HIOX, and VP. However, lactate’s effects on a∗ values were not evident when packaged in CO (P > 0.05). The color-stabilizing effect of CO could have masked lactate’s effect on surface redness. While lactate patties in PVC and VP demonstrated lower (P < 0.05) discoloration than controls, no differences (P > 0.05) existed between controls and lactate samples in CO and HIOX. Our results indicated that the effects of lactate on ground beef color are dependent on packaging.     

Rate of blood loss and timing of exsanguination on prevalence of ecchymosis in fallow deer (Dama dama)

Blood loss associated with four combinations of stunning and exsanguination methods was determined as part of studying prevalence of ecchymosis in slaughtered fallow deer (Dama dama). A fifth treatment simulated incomplete severance of the extended neck after captive bolt stunning. Predicted mean weights of blood collected from the five slaughter treatments, including electrical stunning followed by the thoracic stick method of exsanguination, captive bolt stunning followed by the thoracic stick, captive bolt stunning followed by the gash cut method of exsanguination, electrical stunning followed by the gash cut, and captive bolt stunning followed by incomplete severance of the extended neck, were 1458.7, 1072.7, 684.5, 463.7, and 228.5 g, respectively. The overall effect of exsanguination method was highly significant (p < 0.001) with the thoracic stick resulting in the greatest weight of blood collection in the 10 s period immediately after initiation. The overall effect of stunning method on blood loss was not significant, although there was a significant (p < 0.05) stunning method by exsanguination method interaction. Ecchymosis of varying severity occurred in some carcases from all treatment groups. Using the total loin and round ecchymosis scores, when little or no ecchymosis (grades 0 or 1) was compared with some ecchymosis (?grade 2) by logistic regression, castrated bucks were 9.8 times more likely (p = 0.002) and does 4.2 times more likely (p = 0.06) to have some ecchymosis than entire bucks. The results indicate that ecchymosis can be reduced in fallow deer carcases by thoracic stick exsanguination incorporated less than 10 s after stunning.     

Application of response surface methodology to optimise supercritical carbon dioxide extraction of essential oil from Cyperus rotundus Linn.

Supercritical fluid extraction with carbon dioxide (SC-CO₂ extraction) was performed to isolate essential oils from the rhizomes of Cyperus rotundus Linn. Effects of temperature, pressure, extraction time, and CO₂ flow rate on the yield of essential oils were investigated by response surface methodology (RSM). The oil yield was represented by a second-order polynomial model using central composite rotatable design (CCRD). The oil yield increased significantly with pressure (p < 0.0001) and CO₂ flow rate (p < 0.01). The maximum oil yield from the response surface equation was predicted to be 1.82% using an extraction temperature of 37.6 °C, pressure of 294.4 bar, extraction time of 119.8 min, and CO₂ flow rate of 20.9 L/h.