氩气MAP技术在樱桃保鲜包装中的应用

研究了氩气MAP与不同预处理组合对樱桃常温保鲜性能的影响,并与自然气调包装的保鲜效果进行了比较.结果表明,在相同的包装薄膜(LDPE袋)内,相同的包装期限,氩气MAP能有效的抑制樱桃的腐烂,降低樱桃果实中水分子的活力,延长了樱桃的货架寿命.其中,涂膜结合氩气MAP对樱桃的保鲜效果最佳.     

贮藏温度及包装薄膜对青菜品质的影响

研究了不同贮藏温度和薄膜包装袋对青菜采后贮藏期间生理品质变化的影响,测定了薄膜的透气率和青菜的失重率、呼吸强度、维生素C含量,并进行了感官评价.研究结果表明,低温贮藏和薄膜包装的结合可以有效地抑制青菜的呼吸速率,减少营养成份的损失,延长青菜的货架寿命.同时,使用LDPE无孔密实袋(0.04mm)包装效果最佳.     

植物精油对草莓保鲜效果的影响研究

研究了常温条件下植物精油对草莓保鲜效果的影响。选取2种薄膜(高透氧量的PE薄膜和高阻隔性复合薄膜,分别记为FA膜与FB膜),设置5组试验(空白组,FA膜组,FB膜组,添加精油的FA膜组,添加精油的FB膜组),定期对草莓进行感官评价,并测定其可溶性固形物含量、失重率及Vc含量等技术指标。结果表明,在常温条件下,添加植物精油在一定程度上有利于草莓的保鲜,可以延长草莓的货架寿命;高阻隔性复合薄膜(FB膜)与精油联合应用的保鲜效果较好,是草莓保鲜包装较为有效的方式。     

新鲜红肉的改变气体包装

改变气体包装(MAP)就是将食品密封在高气体阻隔材料内,改变气体环境,降低呼吸速率,减缓微生物生长,抑制酶败坏,达到延长货架寿命的口的。MAP应用于新鲜红肉可分成两种基本技术:真空包装和充气包装。这两种技术所用的包装材料要求具有良好的气体阻隔特性,能延长货架寿     

超市蔬菜用阻光包装膜的研究

为了减小超市灯光中紫外线对包装鲜切西兰花的货架寿命的影响,采用LDPE与紫外线吸收剂UV-531共混的方法制备选择性阻光薄膜,UV-531所占质量分数分别为0,0.1%,0.3%和0.5%。使用制备的4种薄膜和超市现用LLDPE保鲜膜包装鲜切西兰花,置于超市用灯光下进行保鲜研究。结果表明:添加紫外线吸收剂的LDPE薄膜的透光率随着紫外线吸收剂添加量的增加而降低;在室温(29+1)℃条件下,添加紫外线吸收剂的LDPE薄膜对鲜切西兰花的保鲜效果均好于超市现用LLDPE保鲜膜;其中添加量为0.3%时能够更好地保护鲜切西兰花的叶绿素和水分,保鲜效果最好。     

转光薄膜对绿颜色蔬菜品质影响的研究

目的延长绿颜色蔬菜的货架寿命,保护绿色蔬菜品质。方法模拟某超市果蔬区的销售环境,以鲜切西兰花为例,选择单基双能转光剂(RBI),吹制添加质量分数为0.5%,0.8%,1.2%,1.5%,2.0%的低密度聚乙烯(LDPE)薄膜。对转光薄膜的气体透过性和光学性能进行测试,分别将添加不同含量单基双能转光剂的LDPE薄膜包装鲜切西兰花,并置于模拟超市的光照环境下,测定试验样品的质量、维生素C含量、叶绿素含量等变化,并对试验样品进行感官评价。结果对比超市现有绿颜色蔬菜的包装薄膜,在LDPE薄膜中添加适量转光剂可以达到保护鲜切西兰花品质、延长其货架寿命的效果。结论添加质量分数为1.2%单基双能转光剂的低密度聚乙烯薄膜的保鲜效果最好。     

屏蔽紫外线LDPE透明包装薄膜的光学设计及其在油脂食品包装上的应用

通过透射光谱分析研究了自制可屏蔽紫外线LDPE透明包装薄膜的光学性质,并针对透明包装材料透光性对油炸椒盐花生氧化酸败的影响进行了分析研究,建立了描述其货架寿命的数学模型.     

PEO改性纳米TiO2/LDPE复合薄膜的光降解性能

以聚氧乙烯(PEO)改性纳米TiO2颗粒作为光催化剂,与低密度聚乙烯(LDPE)树脂复合制备了一种新型可光催化降解的TiO2/LDPE纳米复合薄膜,进行了该薄膜在空气中紫外光照下的光催化降解实验。通过表面接触角、失重率、红外光谱(FT-IR)和扫描电镜(SEM)等分析技术系统地研究了该复合薄膜的降解性能。结果表明,PEO的加入能提高薄膜的亲水性和TiO2的分散性,提高TiO2的光催化活性,有利于促进LDPE薄膜的降解。TiO2/PEO/LDPE复合薄膜在0.8mW/cm2紫外光强下照射425h,失重率达到15.2%;在4mW/cm2紫外光强下照射500h,失重率达到38.1%。光照后薄膜的拉伸强度和断裂伸长率显著降低,羰基指数升高。     

食品包装中使用除氧剂

在各种包装方法中,使用真空、真空/充气、气体净化等包装方法使易腐败的食品能够维持品质、延长货架寿命,均被称之为气体置换包装(MAP)。最近,澳大利亚引进的除氧剂,使气体置换包装又增加了一种方     

光氧化TiO_2/PEO/LDPE复合薄膜的生物降解性能

以聚氧乙烯(PEO)为亲水改性剂、纳米TiO_2颗粒作为光催化助氧剂,与低密度聚乙烯(LDPE)树脂复合制备了光氧化-生物降解TiO_2/PEO/LDPE纳米复合薄膜。通过密封堆肥和土壤微生物的降解实验,研究了该复合薄膜在空气中紫外光氧化降解后的生物降解性能。结果表明,TiO_2/PEO/LDPE复合薄膜在UVA340的紫外光照射600h后,发生了明显的降解,羰基指数增大,产生了大量羰基类的化合物,结构发生明显的破坏;光氧化后的薄膜碎片经过180d的堆肥或254d的土壤微生物降解后,其矿化率达到15.26%,薄膜表面长满了孢子及大量的菌丝,能够为微生物的生长提供所需的碳源。PEO的加入能提高纳米TiO_2在LDPE基体中的亲水性,从而提高其光催化氧化活性,使得LDPE薄膜的光氧化降解程度明显增大,有利于其后续的生物降解。     

肉桂壳聚糖涂膜处理对草莓保鲜的研究

采用超声辅助方法从中药桂皮中提取肉桂精油.以常温预备实验为基础,将所得肉桂精油配制成4种不同浓度,与1%的酸溶性壳聚糖复配组成复合保鲜液,采用涂膜处理对草莓进行保鲜研究.结果表明:在(23±1)℃的温度条件下,采用保鲜液组对草莓的保鲜效果均好于对照组;复合保鲜液提高了草莓的优果率,降低了失重率,减缓维生素C、可溶性糖和有机酸含量的降低;其中30μL/mL的肉桂精油与壳聚糖复合,保鲜效果最佳,使草莓的货架寿命延长了48h.     

Effect of packaging film on the quality of ‘Chaoyang’ honey peach fruit in modified atmosphere packages

The quality of honey peach fruit stored at 2°C in modified atmosphere packages was studied. Three different thickness low‐density polyethylene (LDPE) films were used as packaging films. Honey peach fruits of ‘chaoyang’ were packaged in LDPE bags 15, 25 and 40µm thick and control (air). The respiration rate, O₂ and CO₂ concentrations in the packages, flesh colour, total soluble solid (TSS), titratable acidity (TA), flesh firmness (FF) and membrane integrity of the fruits were monitored. Compared to the control, MAP treatments inhibited the climacteric peak, avoided the increase of flesh colour, decreased the development of softness and retarded the reduction of TTS, TA and membrane integrity. Significant differences in the quality of the fruits were found between the three packages and the control (p ≤ 0.05). After 20 days at 2°C within the LDPE25 bags, a steady‐state atmosphere of 5% CO₂ + 4% O₂ was reached. Honey peaches stored in these bags showed the best quality at the end of the storage. Copyright copy; 2006 John Wiley & Sons, Ltd.     

Combined effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes

Effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes were studied. Prior to packaging with low‐density polyethylene (LDPE) film (0.02 mm in thickness), tomatoes were immersed in hot water (42.5°C) for 30 min. Control tomatoes were not treated and were stored for 2 weeks at 10°C and then for 3 days at 20°C without packaging. Steady states of O₂ and CO₂ concentrations inside the package were about 5 and 8%, respectively, and were reached after 6 and 4 days of storage, respectively. MAP reduced weight loss of tomatoes to about 41% of that of unpackaged fruit during a 2‐week storage period. The use of a combination of HWT and MAP reduced weight loss and decay, inhibited color development and maintained firmness of tomatoes but had no effect on soluble solids content or titratable acidity. HWT slightly reduced mold growth of tomatoes stored in MAP. Packaging of control fruit in MAP resulted in stimulation of mold growth around the stem end of the fruit after about 1 week of storage and also resulted in cracking and decay. HWT could be used as disinfectant for tomatoes prior to storage in MAP in order to reduce microbial growth, cracking and decay that may be caused by excessive water vapor inside the package. Copyright © 2003 John Wiley & Sons, Ltd.     

纸塑铝包装废弃物水热产油过程组分交互作用

目的 研究纸塑铝复合包装袋中主要组分(纸纤维、低密度聚乙烯和铝箔)水热液化产油特性,分析各组分共液化过程的交互影响作用.方法 采用微型反应釜在温度为360°C,压力为20 MPa,反应时间为30 min条件下,分别对纸纤维、低密度聚乙烯(LDPE)和铝箔单组分、双组分及三组分样品进行水热液化反应,对油品产率、元素组成、成分以及固体残渣形貌等进行表征.结果 单组分纸纤维的生物产油率为13.67％,但其氧含量高达24.19％,单组分低密度聚乙烯(LDPE)在该条件下基本不解聚.双组分纸纤维/LDPE的产油率(14.88％)明显高于单组分的理论产油率(10.75％),且油品中烃类产物显著升高,酮类、酯类和醇类均有所降低.铝箔能显著降低纸纤维液化油品产物的氧含量,提高了油品热值,油品组分中酯类和酚类产物得到明显降低.三组分纸纤维/LPDE/铝箔产油率由理论计算值10.21％提升至19.00％,高热值由28.80 MJ/kg升至30.04 MJ/kg,油品氧含量降低至21.76％,产物组分中酮类组分由28.12％降低至8.96％.结论 纸纤维与LDPE共液化具有显著的协同作用,铝箔在水热条件下对油品实现原位加氢.纸塑铝共液化过程会产生纸塑协同及铝水反应原位加氢的叠加效应.     

基于二乙醇胺/PVA的选择性渗透膜制备及表征

目的制备一种二乙醇胺/聚乙烯醇(PVA)涂覆于低密度聚乙烯的选择性渗透膜,并对其性能进行研究。方法以硅藻土为添加剂、低密度聚乙烯(LDPE)为基膜,以二乙醇胺为胺基载体的复合聚乙烯醇为涂层,通过将涂膜液涂覆在低密度聚乙烯膜上制备新型选择性渗透膜,并研究二乙醇胺载体选择性渗透膜的气体选择性透过性能、二乙醇胺载体对渗透膜结构与性能的影响。结果试验制备的基于二乙醇胺/PVA的选择性渗透膜的CO_2和O_2的渗透系数比值最高可达5.13。结论所制备薄膜提高了CO_2气体渗透率,CO_2和O_2的气体选择性系数。随着二乙醇胺载体含量的增加,复合膜拉伸强度变化不显著,断裂伸长率随着胺基载体含量的增大略有上升。     

深度混炼对纳米SiO2/低密度聚乙烯复合材料分散性与直流电性能影响

利用同向平行双螺杆挤出机对纳米SiO₂/低密度聚乙烯（LDPE）复合材料进行深度混炼,采用SEM、直流击穿强度试验及变温空间电荷试验研究了该工艺对纳米SiO₂/LDPE复合体系中纳米SiO₂颗粒分散性、直流击穿强度和空间电荷特性的影响,综合评估了纳米SiO₂颗粒分散性改善和纳米SiO₂/LDPE复合材料熔融状态下机械剪切降解对电性能的影响。结果表明,随着混炼次数的增加,纳米SiO₂颗粒在LDPE中分散的更加均匀;深度混炼与单次混炼相比,SiO₂/低密度聚乙烯复合材料直流击穿强度上升,室温下达到433.1 kV/mm;随着混炼次数的增加,SiO₂/低密度聚乙烯复合材料低温时抑制空间电荷能力变强,但60℃以上高温时抑制能力变差。混炼次数的增加改善了纳米SiO₂颗粒的分散性,使其与LDPE基体的界面增多,同时,纳米SiO₂颗粒还使SiO₂/低密度聚乙烯复合材料的片晶厚度增大,结晶度升高,界面区和力学性能都随着分散性改善而增加和增强,两者共同促进了SiO₂/低密度聚乙烯复合材料电学性能的改善。但是由于深度混炼引发了材料降解,结构缺陷的增多影响了纳米SiO₂/LDPE复合材料高温区的空间电荷抑制性能。     

Ethylene and oxygen permeability through polyethylene packaging films

Oxygen and ethylene permeabilities have been determined at 19°C for three kinds of polyethylene films (LDPE, LLDPE and HDPE) and in the temperature range 4–30°C for LDPE. At constant temperature, ethylene and oxygen permeabilities decrease with increasing density. The temperature dependence of oxygen and ethylene permeabilities was found to be Arrhenius in the temperature range tested, with activation energies of 47.7 and 44.1 kJ/mol for ethylene and oxygen respectively. Permeabilities were found to be independent of film thickness and oxygen and ethylene permeabilities were independent of the composition of oxygen/nitrogen mixtures. Gas permeabilities for zeolite-filled LDPE films were found to be larger than oxygen and ethylene permeabilities for unfilled LDPE film. The adsorption isotherm of ethylene on the ceramic component of the films has been measured at room temperature: the absorption isotherm corresponds to monolayer adsorption and the adsorption capacity of the ceramic was measured as 3.06 mmol/g. © 1998 John Wiley & Sons, Ltd.     

Properties of antimicrobial plastics containing traditional food preservatives

Traditional food preservatives, sodium benzoate, sodium nitrite, potassium sorbate and sodium lactate, were incorporated into synthetic plastics, low‐density polyethylene (LDPE), poly(maleic acid‐co‐olefine), polystyrene (PS) and polyethylene terephthalate (PET), aimed at producing antimicrobial packaging material for foodstuffs. The study was undertaken on plaques (thickness 2 mm) and films (thickness 70–120 µm), whose antimicrobial test results clearly differed. Plaques containing 15% sodium nitrite inhibited both Aspergillus niger and Bacillus subtilis, whereas the same concentration of sodium benzoate and potassium sorbate had activity only against B. subtilis. Sodium lactate‐containing samples did not have any antimicrobial activity and none of the samples inhibited Escherichia coli. Antimicrobial substances added into PS and PET produced the strongest activities; however, due to the brittle structure of these materials, they were not tested further. Thus, more thorough tests for antimicrobial activity, migration and oxygen and water vapour permeability were carried out using LDPE films with 2.5–15% sodium benzoate and sodium nitrite. The effects of both substances on permeability properties were negligible. Although the total migration into food simulants measured from the films in many cases exceeded the limit value of 10 mg/dm², no antimicrobial activity was observed. Copyright © 2003 John Wiley & Sons, Ltd.