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.     

Physiological responses of Manchega suckling lambs: Effect of stunning with different CO2 concentrations and exposure times

Four groups of Manchega breed suckling lambs, stunned with different CO₂ concentrations and exposure times (G1: 80% CO₂ 90 s; G2: 90% CO₂ 90 s; G3: 90% CO₂ 60 s; G4: 80% CO₂ 60 s) 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% CO₂. 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.     

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.     

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.     

Effects of the rearing season on carcass and meat quality of suckling Apennine light lambs

The aim of this study was to evaluate the effects of the rearing season (autumn vs winter) on the carcass and meat quality of light lambs, obtained according to the traditional farming system usual in central Italy. Eighty carcasses from 60 d ± 3 old unweaned Apennine single birth male lambs, permanently reared indoor, half in autumn (receiving milk from ewes permanently pastured) and half in winter (which dams did never acceded to pasture), were weighed, classified according to the EU classification system for light lambs, and their Longissimus lumborum meat was analysed for pH, colour, drip and cooking losses, proximate composition and fatty acids profile of intramuscular fat. Most of the carcasses fully responded to the 1st quality EU requirements and no effects of the rearing season was evident on carcass characteristics. On the contrary, L. lumborum of lambs born and reared in autumn, receiving milk from ewes permanently pastured, evidenced a lower Lightness L* (P = 0.02), a higher Chroma C* (P = 0.01), with a higher fat content (P = 0.04) than lambs reared in winter, which dams were permanently stall-fed. Moreover the intramuscular fat of the former was characterized by a greater PUFA concentration (P = 0.01), a more favourable n-6/n-3 ratio (P < 0.001), and a higher CLA content (P < 0.001) than the latter, as a result of the difference related to the sheep traditional feeding system.     

Determination of O2 and CO2 transmission rate of whole packages and single perforations in micro-perforated packages for fruit and vegetables

Microperforated packages are in widespread use for whole and fresh-cut fruit and vegetables, and there is a need for a simple and cost efficient methodology to accurately determine gas transmission rates for different packages. This work demonstrates a static technique using a low cost gas analyser for determining the O₂ and CO₂-transmission rates and permselectivity for whole perforated and non-perforated packages stored at different temperatures. The work further demonstrated the possibility to calculate the transmission rates for single holes, and results for single perforations agreed well with results in other studies. The O₂- and CO₂-transmission rates in perforated packages were not significantly affected by temperature in the range 5–23 °C, whereas transmission rates increased with increasing temperature for non-perforated packages. Gas transmission measurements can be used within quality control, in the choice of appropriate packaging for different fruit and vegetables and as an important parameter in EMAP modelling.     

Storage of green coffee in hermetic packaging injected with CO2

The objective of this study was to evaluate the physical, chemical, and sensory qualities of green coffee beans (Coffea arabica L.) during storage in different types of packaging. Coffee was stored from October 2008 to September 2009 in a warehouse of the Agriculture Society Ltda. (SAAG) in Santana da Vargem, southern Minas Gerais State, Brazil. The treatments in the factorial design consisted of two types of packaging (hermetic big bags with the injection of up to 60% CO₂ in a controlled atmosphere; similar bags but without the injection of CO₂ in a modified atmosphere) and three sampling positions in the bags (high, medium, and low). At 3-month intervals during a 12-month period, grains were analyzed to determine their water content, color, electrical conductivity, potassium lixiviation, and content of sugars. Sensory analysis was also conducted at these sampling times. The storage of green coffee beans in hermetic big bags on a commercial scale under modified and controlled atmospheric conditions is viable over a 12-month period. The coffee packed in big bags maintained its quality and exhibited an intensification of the green coloration of the grains during storage. Sensory analysis of coffee beans stored in a controlled atmosphere showed that the medium sampling position yielded the best ratings. The results of this analysis demonstrated that this storage technique can potentially increase the effectiveness of methods used to preserve the sensory quality of coffee beans.     

红提葡萄低O2和高CO2处理效果研究

以红提葡萄为试验材料,研究(0±0.2)℃,2.5%O2+5%CO2、2.5%O2+10%CO2、2.5%O2+15%CO2和8%、10%、12%O2条件下气体处理效果。结果表明:CO2对红提葡萄有明显的抑菌作用,(0±0.2)℃处理50d,2.5%O2协同5%、10%、15%CO2处理比单纯低8%、10%、12%O2处理效果好,腐烂率低,硬度变化小;2.5%O2,5%～10%CO2可以取得较好的保鲜效果;2.5%O2+15%CO2处理50d未见高CO2伤害症状,表明新疆产红提葡萄耐高CO2能力强;单纯低O2贮藏时,O2含量在±2%范围变化时就会对果肉硬度、果胶酶活力、PPO活力及SSC产生显著性影响(P<0.05)。     

CO_2气体保护焊丝焊接飞溅原因及预防措施

介绍CO2气体保护焊丝焊接飞溅原因及预防措施。以ER50-6为例,从CO2气体保护焊丝原料成分、焊丝生产工艺过程控制和焊接工艺参数3方面分析引起焊接飞溅的因素,给出CO2气体保护焊丝焊接时金属飞溅的预防措施:(1)严格控制焊丝原料各成分含量,尤其是C的质量分数不能超过0.08%;(2)加强焊丝生产工艺过程控制,模具6 h更换一次,拉拔油12 h彻底更换一次;(3)选择合适的焊接工艺参数,焊枪倾斜角度不能超过20°,焊丝的伸出长度为直径的10～12倍;(4)在焊丝表面涂覆活性剂;(5)在CO2中加入氩气。以上措施可有效减少焊接过程焊接飞溅的产生。     

Shelf-stability enhancement of precooked red claw crayfish (Cherax quadricarinatus) tails by modified CO2/O2/N2 gas packaging

Three types of packaging systems were compared for their influence on the storage stability (2 °C) of precooked and peeled red claw crayfish tails. Modified atmosphere packaging (MAP; with 80%CO₂/10%O₂/10%N₂) almost totally inhibited the growth of aerobic bacteria and coliforms when compared with aerobic polyvinylchloride packaging (PVCP) and vacuum packaging (VP). MAP also prevented a pH rise, purge loss, and texture toughening or softening of stored red claw when compared with PVCP or VP (P<0.05). Lipid oxidation was minimal in all three packaging systems. Thus, MAP offers an attractive means to preserve the shelf life of precooked red claw stored under refrigerated retail display conditions.     

不同浓度CO2对箱式气调贮藏树莓保鲜效果的影响

以Heritage品种树莓作为试验材料,采用塑料气调保鲜箱,通过分析贮藏过程中箱内O2、CO2气体、果实感官及主要生化指标的变化,研究了不同体积分数CO2对树莓鲜果贮藏保鲜效果的影响。结果表明:CO2处理对箱式气调贮藏树莓的保鲜效果具有一定影响,其中,CO2体积分数为5%的处理,贮藏过程中箱内CO2和O2体积分数变化幅度均较小,果实PPO活性的升高和MDA的积累受到一定的抑制,果实POD活性维持了较高水平,贮藏至40d时果实色泽基本无变化,香气略变淡,仅个别果实表面有零星水珠出现。由此表明,CO2体积分数为5%更适宜树莓箱式气调贮藏,维持果实品质。     

CO2跨临界双级压缩制冷系统的(火用)分析

目的:提升CO₂跨临界双级压缩制冷系统性能。方法:对该系统进行了常规(火用)分析与高级(火用)分析,围绕内源可避免(火用)损失、内源不可避免(火用)损失、外源可避免(火用)损和外源不可避免(火用)损失这4个方面进行各部件(火用)损失计算。结果:CO₂跨临界双级压缩制冷系统有很大提升效率的潜力。常规(火用)分析与高级(火用)分析所得优化部件的优先级不同。高、低压级压缩机和蒸发器的性能优化是提高系统能效的重点。结论:高、低压级压缩机和蒸发器的内源可避免(火用)损失分别占系统总内源可避免(火用)损失的20.9%,15.2%,36.5%,且通过改进高、低压级压缩机和蒸发器可分别减少其58.8%,49.3%,90.2%的(火用)损失,常规(火用)分析无法提供此类建议。     

磷化氢与二氧化碳混合熏蒸试验报告

用仓外混合熏蒸机以磷化氢和二氧化碳混合熏蒸方式处理有虫小麦，结果表明，用这种新方法能够大大提高磷化氢（PH3）的渗秀速度和杀虫效果，具有投资少，操作简便，防治效果好的特点。     

不同季节工况下变转速NH3/CO2复叠制冷系统性能研究

目的：研究在不同季节工况、蒸发温度为25 ℃条件下,高温压缩机转速对NH₃/CO₂复叠制冷系统性能的影响。方法：建立NH₃/CO₂复叠制冷系统模型并验证其可靠性,计算分析高温压缩机转速与系统高温蒸发温度、高温排气温度、中间温度、高温压缩机功率、制冷量、性能系数的变化关系。结果：仿真模型对制冷量的预测与理论值的相对误差小于14.1%。高温压缩机转速从2 300 r/min增至3 300 r/min,春季、夏季、秋季、冬季工况下的制冷量分别提升了31.7%,41.7%,33.9%,25.2%,且在低转速范围内冬季制冷量最高;高温压缩机功率呈两段式上升趋势,提升了40%～45%。结论：存在使得性能系数最大的最佳高温压缩机转速。基于系统对不同季节工况的适应性问题,提出了变转速NH₃/CO₂复叠制冷系统方案,与定转速系统相比每年可减少19.9%耗电量。     

龙眼核油的超临界CO2萃取及其抗氧化性研究

对龙眼核油的超临界CO2萃取条件进行了单因素实验研究,并确定了适宜的萃取条件:萃取压力20 MPa、龙眼核粒度60～ 80目、萃取温度40℃、解析温度35℃。采用气相色谱-质谱联用(GC-MS)方法对龙眼核油进行了成分分析,共检测出22种化合物。研究了龙眼核油对花生油和猪油的抗氧化性,实验结果表明,龙眼核油有较明显的抗氧化活性。     

Effects of supercritical CO2 and N2O pasteurisation on the quality of fresh apple juice

Supercritical pasteurisation is receiving increasing attention as an alternative technology for foodstuff pasteurisation, but often the possible effects on the perceptible quality are not sufficiently considered.     

超临界CO2提取板栗油工艺优化研究

利用冷冻干燥板栗粉为原料,探讨了影响超临界CO_2提取板栗油的工艺参数,采用PlackettBurman设计实验和Central Composite设计实验优化了板栗油提取工艺。利用Plackett-Burman实验,从影响板栗油提取因素中筛选出提取温度和提取时间2个显著影响因素。以显著影响因素为基础,经过最陡爬坡实验,获得40℃提取温度和120 min提取时间可以逼近最大板栗油提取率区域,并以此作为中性组合实验中心。中心组合实验获得板栗油提取率回归方程和板栗油优化提取工艺,回归方程达到显著水平(F=60.58,P0.000 1),拟合很好(R_(Pred)~2=0.842 6,R_(Adj)~2=0.961 1);超临界CO_2提取板栗油优化工艺参数:板栗粉为60目、提取压力为30 MPa、提取剂流量为20 L/h、提取温度为43℃、提取时间为140 min。优化实验参数条件下,板栗油提取率均值为82.15%。     

Extraction of alkylresorcinols from wheat bran with supercritical CO2

The supercritical fluid extraction (SFE) of wheat bran alkylresorcinols has been studied. Extractions were carried out at 40.0 MPa. The effect of particle size, static extraction pretreatment with supercritical CO₂ (SC-CO₂) and extraction temperature on the extraction kinetics was investigated. The extraction yield increased as the particle size decreased and with temperature. Extraction curves present a faster and linear initial extraction period followed by a slower extraction period. Based on these results the approximate mathematical model of Sovová was successfully applied to describe the extraction curves. The total content of alkylresorcinols was determined and compared with the alkylresorcinol content obtained by conventional organic solvent extraction. Due to the amphiphilic nature of these resorcinolic lipids, the extraction yield was higher for polar organic solvents than for SC-CO₂. Characterization of supercritical extracts was also performed by determining the fatty acid composition and antioxidant activity.