复烤片烟醇化过程耗氧规律及其影响因素分析

为考察复烤片烟醇化过程消耗氧气的规律特征及其影响因素,在山东诸城仓库对8个代表性等级复烤片烟密封垛内的氧气浓度、温度、湿度进行了3年的跟踪监测,分析了垛内氧气浓度、烟叶醇化耗氧速率随贮存时间的变化规律及温度、相对湿度、氧气浓度对耗氧速率的影响。结果表明：①复烤片烟醇化过程伴有较明显的耗氧现象,年度最大耗氧速率逐年降低,年度内呈现季节性变化。②烟叶耗氧速率受温度影响最大,在本试验条件下,温度超过20℃时,耗氧速率呈线性增加趋势。③不同醇化阶段烟叶耗氧速率受氧气浓度影响程度不同,醇化第2年、第3年烟叶耗氧反应充分进行所需氧气浓度下限分别为14%和8%,在氧气浓度小于6%时烟叶耗氧反应明显减弱。复烤片烟醇化过程所需氧气供应随醇化周期、贮存环境而改变,在气调养护时可对垛内氧气浓度做针对性调控,以便于提高烟叶醇化质量、节约养护成本。     

一种旋转密封送料阀氮气置换仿真分析

某真空密闭系统要求系统内氧气浓度低于一定值(8%),系统中旋转密封送料阀是系统内外的主要漏点。文章采用充氮方式对旋转阀进行氮气置换保障隔氧效果,并对该过程进行了仿真分析,考察了不同充氮量下的氮气隔氧效果。结果表明:在旋转阀通入氮气流量为60m3/h时,可以在2s以内可以将叶片空腔的氧气浓度降低到8%以下,满足氮气置换要求,采用氮气置换进行系统隔氧的技术措施有效而且可行。     

小贮氧瓶简易充氧

为安全计,我厂购进两套背负式 AHG—2型氧气呼吸器,供救护人员在有害气体环境中佩带进行工作呼吸用。容积为1升,工作压力200kg/cm~2贮氧瓶壹只,氧瓶在200kg/cm~2压力时贮存氧气200升可供救护人员使用两小时,氧气用完须另行充氧,为充氧方便,我们把气割用氧气充入贮氧瓶,方法是:     

纸浆中浓氧漂试验

中浓氧漂是目前在国外应用日益广泛的一种氧气漂白方法。它与应用较早的高浓氧漂相比较,主要有以下区别: 1.氧漂浓度不同,中浓氧漂纸浆浓度为8～12％,高浓氧漂纸浆浓度为20～30％。 2.浆与氧气的混合方式不同。高浓氧漂时氧气主要是以渗透方式从气相传递到纸浆中去,而中浓氧漂时,主要是靠机械搅拌作用达到使氧气与浆充分混合的     

活性氧的信号转导功能

氧气是地球上需氧生物维持生命所必需的,过去人们以为,氧对需氧生物有益无害。研究表明,在需氧生物利用氧气的代谢过程中,会产生一类含有氧的比氧气性质还活泼的物质—活性氧(reactiveoxy-genspecies,ROS),它包括过氧化氢(H2O2)、超氧阴离子(O2·ˉ)、羟自由基(·OH)等,可与细胞内的生物大分子反应,引发氧化损伤。白内障、肺水肿、糖尿病,肌肉萎缩、营养缺乏、精神病等都与氧化损伤有关。但近年的研究发现,活性氧在细胞的增生、分化、凋亡等的调控中也起重要作用,被认为是一种新的第二信使[1,2]。     

高氧气调包装肉类研究进展

肉类高氧气调包装通常是用含有70%~80%的氧和20%~30%的二氧化碳的混合气体对新鲜肉类进行包装的技术,其中的氧气可使肉类呈现稳定的红色,二氧化碳主要是抑制细菌的生长而延长贮藏期限。本文对近年来该技术在新鲜肉类中应用的研究情况进行了总结,从高氧包装对肉类颜色的影响、高氧环境下的微生物生长、高氧对肉类的脂类氧化和蛋白质氧化的影响以及提高高氧气调包装肉类品质的措施等方面进行了评述。肉类的颜色稳定性与肌肉类型有关,随O2浓度的增加而增大,随CO2浓度的增加而降低。另外,肉类颜色稳定性受肉类氧化特别是脂类氧化的影响。高氧气调包装肉类中的微生物受到CO2的抑制作用表现出比生长速率降低及生长的迟滞期延长。高氧气调包装会引起脂类和肌红蛋白的氧化以及蛋白质的交联,导致肉的嫩度和多汁性下降。高氧气调包装会导致肉类煮制时出现过早熟褐现象。添加某些防腐剂和抗氧化剂可以有效改善高氧气调包装肉类质量,延长肉类贮藏期限。     

氧碱麦草浆的氧漂

在这项研究中,用氧碱法制取的麦草浆实现了氧碱漂白。首先用下面列出的制浆条件蒸煮得到足够数量的氧碱麦草浆。用碱量:16％最高温度:110℃最高温度时间:45分氧气压力:5kg/cm~2 液比:1:4 然后,用绝干氧碱麦草浆各300g进行了19次漂白实验,为了确定最佳氧漂条件,各参数、如:NaOH％处理时间、氧气压力以及浓度在下列指定的范围内变化: NaOH:4％,8％,12％处理时间:20分,30分,40分氧气压力:5kg/cm~2,10kg/cm~2 浓度:20％—12.5％在这些实验中,用固定温度常数110℃,取得的数据通过统计分析,获得了最佳氧漂条件如下: NaOH:4％处理时间:20分氧气压力:10kg/cm~2 浓度:12.5％温度 110℃     

脱氧剂的制备

脱氧剂又名氧气吸收剂。把脱氧剂和内容物一起用密封袋或容器包装,能除去包装系统内的游离氧、溶存氧或渗透氧,抑制内容物的变化,保持内容物原来的品质。因为脱氧剂比其它食品保藏方法的效果好、使用方便、安全、用途广和经济等优点,因此它不但可用于加工     

吸氧型阻隔包装材料对橙汁品质的影响

以吸氧型阻隔薄膜和氧阻隔薄膜为橙汁包装材料,研究不同包装材料对橙汁理化品质和感官品质的影响。贮存期内,氧阻隔薄膜包装果汁的保鲜效果较差,在第2周时,果汁中的维生素C含量降低为零且失去橙汁香气;吸氧型阻隔薄膜包装的橙汁VC含量、可溶性固形物含量和感官评价要高于氧阻隔薄膜,且褐变指数明显低于氧阻隔薄膜。结果表明:吸氧薄膜可以有效清除包装袋内氧气,阻隔外界氧气的进入,在贮存期内形成无氧环境,有利于延长货架期。     

A12O3薄膜包装材料工艺参数与阻隔性的实验研究

采用直流反应磁控溅射工艺,进行了一系列在PET塑料薄膜表面沉积氧化铝的实验,研究了氩气(Ar)、氧气(O2)和溅射功率对所制备的A12O3薄膜透氧率和透湿率的影响.实验表明,当氩气流量为90sccm、氧气流量为10sccm、溅射功率为600W时,A12O3薄膜的透氧率为2.11cm3/(m2×atm×24h),透湿率为0.58g/(m2×atm×24h),此时薄膜阻隔性能最好.     

抗坏血酸对大豆蛋白乳液抗氧化稳定性的研究

本试验通过研究抗坏血酸对大豆蛋白乳液体系中油脂的抗氧化作用,明确抗坏血酸作为天然抗氧化剂在乳化体系中的抗氧化机理。本研究采用溶解氧(DO)和顶空氧气消耗法测定大豆蛋白乳液体系在pH 3.0的环境下抗坏血酸对乳液体系氧消耗的影响;验证不同过渡金属Fe~(2+)、Cu~+对抗坏血酸在乳液中清除自由基能力、降解速率、乳液粒径变化和对大豆蛋白乳液氧化稳定性影响。研究表明:通过激光粒度仪分析乳液在储存期间的粒径变化趋势相同,含有抗坏血酸的乳液与对照组没有明显区别,加入金属离子的乳液粒径偏大;15 mmol/L抗坏血酸能够几乎完全消耗乳液体系中溶氧量;抗坏血酸能够在过渡金属Fe~(2+)和Cu~+发生促氧化时通过转移电子和清除体系中的自由基起到抗氧化作用;与对照组相比,Fe~(2+)和Cu~+可加速抗坏血酸降解和氧的消耗,但并没有引起乳液氢过氧化物和己醛含量的快速增加。说明抗坏血酸在大豆蛋白乳液体系中可通过清除自由基和加速乳液体系中氧消耗的多种机制稳定乳液。     

Oxygen Uptake and ß-Carotene Decoloration in a Dehydrated Food Model

Oxygen uptake of a model system containing β-carotene was measured by a method capable of determining headspace oxygen and entrapped oxygen, both at low concentrations. β-Carotene was determined colorimetrically at 460 nm. A first-order mechanism was found for this reaction with respect to β-carotene concentration as measured by color. The values of the rate constants were functions of the oxygen concentrations in the headspace of samples; they increased as these concentrations increased. Up to seven molecules of oxygen were consumed as each molecule of β-carotene was discolored. This high oxygen consumption was not related to the oxidized products. A mathematical model was developed, based on the experimental data, to predict β-carotene decoloration by measuring oxygen uptake or to determine oxygen uptake from decoloration. A computer program was developed to make these predictions. Samples with known histories had linear correlations between oxygen uptake and β-carotene decoloration. The results for 1% and 2% headspace oxygen concentrations agreed with experimental values, presenting a standard deviation compatible with the experimental methods used. An important corollary is the suitability of a simple colorimetric test for monitoring oxygen uptake in a dehydrated system.     

Synergistic effect of active oxygen species and alginate on chitinase production by Wasabia japonica cells and its application

The specific chitinase productivity of a Wasabia japonica cell suspension culture under pure oxygen aeration was 3.8 times higher than that of a suspension culture aerated with ordinary air. During aeration with pure oxygen, both oxygen consumption by the cells and the H2O2 concentration in the medium increased. Addition of H2O2 to the cultivation medium also promoted the specific chitinase productivity. H2O2 could pass freely through the cell membrane. It was assumed that the excess oxygen was converted into active oxygen species such as H2O2, and that the promotion of chitinase production was probably due to the generated active oxygen species. Addition of alginate oligomer (AO, an endogenous elicitor-like substance) to cultures aerated with pure oxygen or supplemented with H2O2 resulted in synergistic increases in chitinase production. Based on these results, the development of a simple and efficient chitinase production system was investigated. Cells were immobilized in alginate gel (instead of adding AO to the medium) and cultivated in a medium containing H2O2. The specific chitinase productivity increased to the levels observed in the suspension culture system. During repeated batch cultivation of immobilized cells, the chitinase production remained stable for three repeated batches. When immobilized protoplasts were cultivated in a medium containing H2O2, there was 7-fold increase in chitinase production compared with that of immobilized cells.     

A simple screening procedure for heterotrophic nitrifying bacteria with oxygen-tolerant denitrification activity

Various naturally occurring strains of heterotrophic nitrifying bacteria were isolated by enrichment culture using acetamide as the C and N source, and 21 strains were identified as heterotrophic nitrifiers. Using a new simple procedure, these 21 strains were also investigated for the ability to carry out denitrifcation in the presence of oxygen. Several of the nitrifying strains were found to exhibit a distinct activity that allows for denitrifcation via nitrite (NO2-) in the presence of oxygen, indicating that they have an oxygen-tolerant denitrifcation system. A wide variety of bacteria possessing both nitrification and denitrifcation capabilities in the presence of oxygen were isolated and partially characterized by using the simple screening combinatorial procedure described in this paper.     

Development of oxygen scavenging system containing a natural free radical scavenger and a transition metal

A natural free radical scavenger, α-tocopherol, and a transition metal in an oxygen scavenging system were evaluated as a possible oxygen scavenger. The effects of α-tocopherol, transition metal, moisture, and thermal processing on oxygen scavenging capability were investigated. An initial, cup headspace oxygen content (%) of 20.9% was decreased to 18.0% after thermal processing and 60 days of storage at room temperature when the oxygen scavenging system containing α-tocopherol (500 mg) and transition metal (100 mg) was utilised. α-Tocopherol and a transition metal were required for optimum oxygen scavenging capability, otherwise the oxygen scavenging capability decreased. The oxygen content (%) decreased further to 17.1% when the amount of transition metal increased from 100 to 150 mg. In this research, α-tocopherol (500 mg) and transition metal (150 mg) had an oxygen scavenging capacity of 6.72 ml O₂/g and an oxygen scavenging rate of 0.11 ml O₂/g•day. Results indicated that α-tocopherol and transition metal in oxygen scavenging system coupled with thermal processing can be used as an effective oxygen scavenger.     

啤酒过滤系统溶解氧的控制

溶解氧是影响啤酒质量的重要因素，过滤系统是目前控制溶解氧及抗氧化的重点。目前，过滤系统存在的溶解氧控制问题有：脱氧水制备量不足；CO2回收量不足，造成过滤或灌装车间用空气背压；添加硅藻土时，未用脱氧水调浆，也未用CO2封闭加料罐口；系统中进酒，出酒管路过长等。控制要点，过滤前用清水充满进酒管路；清水注满捕集器和精滤设备，再用CO2顶尽其中的水，清酒罐采用CO2底部背压，过滤进，硅藻土应充分搅拌，尽可能排出其中空气；过滤清酒时，防止泵空转，清酒罐至灌装酒等管洗涤结束后走脱氧水，防止啤酒吸氧。     

氧载体生物反应器的研究

本文探讨在深层培养条件下利用全氟化碳作为氧载体的一种新的供氧方法,在一喷射自吸式反应器中氧通过氧载体的循环传递给培养液。采用这种供氧方法,反应器的供氧速率可提高2.3倍。     

Novel natural phenolic compound-based oxygen scavenging system for active packaging applications

An oxygen scavenging system containing a natural phenolic compound, pyrogallol with sodium carbonate, was developed and analyzed as a possible oxygen scavenger. The effect of several parameters, including the amount of pyrogallol and sodium carbonate, relative humidity and storage temperature, on the oxygen scavenging capability were investigated. The initial, glass vial headspace oxygen content (%) of 21.1 % (v/v) decreased to 0.26 % after 8 days of storage at room temperature when the oxygen scavenging system used a 1:1 (w/w) ratio of pyrogallol (250 mg) and sodium carbonate (250 mg). Both pyrogallol and sodium carbonate were required for optimum oxygen scavenging, otherwise the oxygen scavenging ability decreased. The oxygen content (%) decreased further to 6.55 % (v/v) when the amount of sodium carbonate decreased from 250 to 166 mg, which yielded a 2:1 ratio. In the present study, pyrogallol (250 mg) and sodium carbonate (250 mg) had highest oxygen scavenging capacity of 51.81 mL O₂/g and an oxygen scavenging rate of 6.48 mL O₂/g day. The oxygen absorption kinetics rate of pyrogallol and sodium carbonate confirmed that the material has good efficiency for use as an oxygen scavenger. Results indicated that the pyrogallol based oxygen scavenging system with moisture activation can be used as an effective oxygen scavenger for low water activity food packaging applications.     

Effect of dynamic process conditions on nitrogen oxides emission from a nitrifying culture

Nitric oxide (NO) and nitrous oxide (N2O) emissions from nitrifying ecosystems are a serious threat to the environment. The factors influencing the emission and the responsible microorganisms and pathways were studied using a laboratory-scale nitrifying reactor system. The nitrifying culture was established at growth rates relevant to wastewater treatment plants (WWTPs). During stable ammonia oxidation, 0.03% of ammonium was emitted as NO and 2.8% was emitted as N2O. Although mixed cultures were used, clear responses in emission of ammonia oxidizing bacteria (AOB) could be detected and it was concluded that the denitrification pathway of AOB was the main source of the emissions. Emissions of nitrogen oxides in the system were strongly influenced by oxygen, nitrite, and ammonium concentrations. Steady state emission levels greatly underestimate the total emission, because changes in oxygen, nitrite, and ammonium concentrations induced a dramatic rise in NO and N2O emission. The data presented can be used as an indication for NO and N2O emission by AOB in plug-flow activated sludge systems, which is highly relevant because of the atmospheric impact and potential health risk of these compounds.     

Oxygen Absorption Properties of Powdered Iron

Powdered iron with a particle size < 10 μm was used as the basic oxygen scavenging system in air-filled glass containers. The scavenger was tested unpackaged or sealed in polyethylene pouches. Scavenger concentration and packaging system affected rates of oxygen removal. Relative humidity markedly influenced the effectiveness of the oxygen scavenger system. At 98% RH, oxygen concentration in air-filled containers reached 1.6% after 21 hr, while one-half of the oxygen remained at 65% RH. Overall, the data suggest =1 to 1.5% oxygen removed per hour at 22 ± 2°C depending on the RH values of the system.