超高压处理对椰肉原浆保鲜的影响

为了研究适宜的椰肉原浆的保藏方法,将椰肉原浆经过600MPa压力,保压时间10min,保压温度30℃条件下处理后在0～5℃条件下贮藏16d,分析超高压处理对贮藏期间椰肉原浆的菌落总数、色泽、pH、电导率影响.结果表明:与对照组相比,超高压处理后可以明显抑制微生物的生长.L、a、b值、电导率有所下降,pH升高,但在储藏期间其变化比较缓慢,在一定程度上延缓了椰肉的品质改变.所以超高压技术是一种较好的椰肉原浆保鲜的方法.     

超高压灭菌效果实验研究

超高压灭菌技术是一项具有广阔应用前景的食品加工新技术。本文以食品中常见的大肠杆菌、枯草芽孢杆菌为研究对象,通过实验对影响超高压灭菌效果的处理条件(压力、保压时间、pH值等)进行了考察与评价。实验结果表明:压力、保压时间对灭菌效果影响显著,随着压力的增大和时间的增长,细菌的死亡率增大。但当处理压力和和保压时间达到一定值后,它所对灭菌效果的影响趋于平缓。强的酸性和碱性环境中,即在低pH值和高pH值时,有利于超高压杀菌,在中性环境中,灭菌效果最差。同时,本文对超高压处理后大肠杆菌的活性进行了研究,得出大肠杆菌经超高压处理后活性降低的结论。研究结果对进一步优化超高压杀菌工艺具有一定的参考价值。     

超高压下食品包装的传质与微观结构的研究进展

超高压(high pressure processing,HPP)处理技术在对食品杀菌、钝酶的同时较好的保留了食品风味与营养物质,具有良好的发展前景。为保障超高压食品安全,研究超高压对包装材料传质性能,即迁移、吸附和渗透的影响至关重要。此文综述了超高压技术对包装材料传质性能的影响,超高压处理条件、包装材料组成、扩散物和食品的性质等是影响超高压下包装材料传质性能的重要因素。通过阐述超高压影响包装材料的微观结构,探讨了超高压下包装材料中扩散物质进行缓慢蠕动的扩散机理,材料传质性能降低的原因。该文还展望了超高压食品包装安全领域研究的发展方向,旨在为超高压食品包装材料传质的研究、材料的设计与应用提供参考。     

纳米包装材料延长金针菇贮藏品质的作用

通过制备一种含纳米Ag、纳米TiO2和凹凸棒土等纳米粉体的聚乙烯(PE)薄膜,用于金针菇的包装贮藏。以普通聚乙烯(PE)薄膜为对照,研究4℃低温贮藏15d期间,纳米包装材料对金针菇保鲜品质的影响。结果表明,贮藏15d后,纳米处理组的金针菇与普通聚乙烯包装处理组相比,较好地保持了贮藏前的洁白色泽,且无明显开伞、水渍状斑块及霉变现象。纳米包装金针菇的褐变度为1.56,相对电导率为6.27%,均显著低于对照(P＜0.01)。而总糖、还原糖和可溶性蛋白质的保留量分别达70.9、11.34mg/g和19.54mg/g,分别高出对照组10.52%、33.53%和22.13%。纳米包装材料能够有效地减缓金针菇采后衰老和品质劣变进程,提高其综合贮藏品质,延长贮藏时间。     

超高压处理对生牛乳中微生物的影响

作为非热杀菌技术的一种,超高压技术在保证灭菌效率的同时能有效保留牛乳中的营养物质。本实验主要以工作压力、保压时间和保温时间3个因素为变量,通过单因素和正交试验,研究不同条件下超高压处理对生牛乳中微生物的杀灭效果。结果表明,超高压处理能够显著杀灭生牛乳中的微生物,且灭菌效果会随着工作压力和保压时间的增加而有所提升,保温时间则没有明显促进作用。通过正交试验初步筛选出了超高压处理生牛乳的最优工艺组合为工作压力600 MPa、保压时间15 min、保温时间30 min。经此条件处理的超高压杀菌乳在2～6℃条件下贮藏30 d后,其微生物结果才超出评测标准。因此,超高压处理可在一定程度上有效延长巴氏杀菌乳的货架期,有利于扩大其销售半径。     

超高压对冷藏带鱼段的保鲜效果

研究了超高压预处理对4℃冷藏带鱼段保鲜效果的影响。试验以4℃冷藏带鱼段做对照,设置不同压力和保压时间(220 MPa、290 MPa,3、6、9 min)对带鱼进行超高压预处理后4℃贮藏,共7个试验组,每隔1天测定感官评定、菌落总数(TPC)、持水力(WHC)、挥发性盐基氮(TVB-N)、三甲胺氮(TMA-N)和硫代巴比妥酸(TBA)等指标。结果表明:超高压能有效抑制菌落的增殖,压力越高,保压时间越长,抑制作用越明显。冷藏组带鱼的货架期为4 d,220 MPa组的货架期延长至10 d,290 MPa组的货架期延长至12 d。随着压力的增大、保压时间的延长,超高压处理后鱼肉的透明度减少,持水力有所降低,但能有效抑制TMA-N的增长速度,并在一定程度上抑制带鱼的脂肪氧化。新鲜带鱼超高压处理后的TVB-N会随着压力的增大有所增加,在贮藏过程中,冷藏组的TVB-N的增长速度逐渐超过超高压组,且保压时间越长、压力越大,抑制TVB-N作用越好。其中290 MPa、6min超高压处理组,290 MPa、9 min超高压处理组保鲜效果最好,贮藏12 d时,带鱼的细菌总数分别为6.19、6.04 lg(CFU/g),TVB-N分别为19.87、20.86 mg N/100 g,基本都处在带鱼二级鲜度之内。     

超高压处理牡蛎灭菌实验研究及人工神经网络模拟

超高压灭菌技术是一项具有广阔应用前景的食品加工新技术.本文以牡蛎为研究对象,通过实验对影响超高压灭菌效果的处理因素(压力、保压时间、温度、施压方式等)进行了考察与评价.实验结果表明:压力、保压时间对灭菌效果影响显著,随着压力的增大和时间的增长,细菌的灭活率增大.温度、施压方式等因素对牡蛎中菌群总数的灭活率影响不大.同时,本文将人工神经网络(ANN)应用到超高压食品处理研究中,利用BP网络模拟超高压灭菌效果,与实验结果比较,测试平均相对误差0.91%,模拟相对误差小于1.8%,模拟准确.研究结果对牡蛎的超高压处理工艺具有一定的参考价值.     

超高静压对食品真空复合包装膜材料性能及微观结构影响的初探

食品包装材料性能及结构变化会影响食品的质量安全及货架期,探索超高静压对食品包装材料性能及结构变化对了解超高静压对包装材料作用效应机理及包装材料选择是有益的。选择2种食品包装最为常用的未拉伸聚丙烯/尼龙/聚乙烯(CPP/nylon/PE)和聚丙烯/铝/聚乙烯(PP/Al/PE)复合包装膜为研究对象,探讨了不同超高静压强对包装材料拉伸强度、拉伸伸长率、热封强度、透气性、透湿性的变化等影响,并对超高静压对包装材料断面结构的影响进行了环境扫描电镜(ESEM)观察。试验结果表明:(1)超高静压处理对CPP/nylon/PE和PP/AL/PE复合材料拉伸强度影响变化不显著;(2)经超高静压处理后,CPP/nylon/PE伸长率及透氧系数变化显著(P<0.05);(3)经超高静压处理后,PP/Al/PE热封强度、透湿率变化显著(P<0.05)、伸长率及透氧系数变化极显著(P<0.01);(4)在一定压强的超高静压处理会使复合膜结构产生膜间裂缝及Al膜内部裂缝。对CPP/nylon/PE在300-600MPa,PP/AL/PE在200-600MPa,基本上是压强越大,裂缝就越严重。     

不同阻隔性包装材料对生菜保鲜效果的影响

为了研究不同阻隔性包装材料对采后生菜保鲜效果的影响,选择低密度聚乙烯膜(LDPE)、聚乙烯膜(PE)、高密度聚乙烯膜(HDPE)、乙烯—乙烯醇共聚物/聚乙烯复合膜(EVOH/PE)4种包装材料对生菜进行气调包装,并设置无包装组作为对照,置于4℃的冷库中贮藏。贮藏期间,定期对各组生菜感官、失重率、叶绿素含量、相对电导率以及袋内气体组分等指标进行测定。结果表明,第6天时,对照组生菜因失水严重而失去商品价值;EVOH/PE组中O_2即将耗尽,CO_2比例达到20.3%,袋内出现酒精气味;其它3组袋内O_2比例均先降低,在小范围内呈波动性变化,CO_2比例先升高后相对平稳。HDPE组贮藏时间达18d,保鲜效果最好。阻隔性适宜的包装材料可以有效提高生菜的保鲜效果,延长保鲜期。     

超高压处理对LDPE、PA6食品包装材料包装性能可逆性的研究

本文在不同条件下对LDPE、PA6进行超高压(HPP)处理,测定不同压力、保压时间及存储时间对材料拉伸强度、热封性能、阻隔性能、热性能以及包装性能可逆性的影响。实验表明:处理压力、保压时间及存储时间对2种材料的热封性均未产生显著影响,但LDPE、PA6试样的拉伸强度随压力升高明显增大;当压力300 MPa时LDPE的透湿性逐渐上升,当压力300 MPa时LDPE的透湿性又逐渐降低,对PA6来说,当压力100 MPa时,材料的透湿性明显下降由10.13 g/(m2·d)(0.1 MPa/10 min)降低到6.79 g/(m2·d)(200 MPa/10 min),但随压力增大透湿性下降的幅度并不明显;两种材料的熔融焓在HPP下均有升高,当存储24 h后,两种材料的ΔH又有所恢复;与0.1 MPa下相比,经过HPP后对异丙基甲苯在LDPE(500 MPa)和PA6(100 MPa)薄膜中的渗透率分别降低约50%和58%,但随着存储时间的延长又逐渐恢复至常压下的渗透率。研究发现实验中采用的LDPE和PA6 2种薄膜的包装性能均有可逆现象出现。     

Migration and sensory properties of plastics-based nets used as food-contacting materials under ambient and high temperature heating conditions

Overall migration from a wide range of commercial plastics-based netting materials destined to be used as either meat or vegetable packaging materials into the fatty food simulant isooctane or the aqueous simulant distilled water, respectively, was studied. In addition, sensory tests of representative netting materials were carried out in bottled water in order to investigate possible development of off-odour/taste and discoloration in this food simulant as a result of migration from the netting material. Sensory tests were supplemented by determination of the volatile compounds' profile in table water exposed to the netting materials using SPME-GC/MS. Test conditions for packaging material/food simulant contact and method of overall migration analysis were according to European Union Directives 90/128 (EEC, 1990) and 2002/72 (EEC, 2002). The results showed that for both PET and polyethylene-based netting materials, overall migration values into distilled water ranged between 11.5 and 48.5 mg l^-1, well below the upper limit (60 mg l^-1) for overall migration values from plastics-packaging materials set by the European Union. The overall migration values from netting materials into isooctane ranged between 38.0 and 624.0 mg l^-1, both below and above the European Union upper limit for migration. Sensory tests involving contact of representative samples with table water under refluxing (100°C/4 h) conditions showed a number of the netting materials produced both off-odour and/or taste as well as discoloration of the food simulant rendering such materials unfit for the packaging of foodstuffs in applications involving heating at elevated temperatures. GC/MS analysis showed the presence of numerous volatile compounds being produced after netting materials/water contact under refluxing conditions. Although it is extremely difficult to establish a clear correlation between sensory off-odour development and GC/MS volatile compounds' profile, it may be postulated that plastics oxidation products such as hexanal, heptanal, octanal and 2,6 di-tert-butylquinone may contribute to off-odour development using commercially bottled table water as a food simulant. Likewise, compounds such as carbon disulfide, [1,1'-biphenyl]-2-ol and propanoic acid, 2 methyl 1-(1,1-dimethyl)-2-methyl-1,3-propanediyl ester probably originating from cotton and rubber components of netting materials may also contribute to off-odour/taste development.     

射频杀菌对PE、PP包装材料外观及力学性能的影响

研究射频(Radio Frequency,RF)处理对常用包装材料的影响,为射频场下食品包装材料的选择提供参考。本文研究了射频处理时间(1、2、3、5、7 min)对不同包装材料外观及力学性能的影响。其中内装物选择水、体积分数3%乙酸、体积分数15%乙醇、橄榄油作为四种食品模拟物,外包装材料选择聚乙烯(PE)和聚丙烯(PP)。结果表明,PE和PP包装材料分别在射频处理3、5 min后,包装件的边缘出现熔化现象。对射频处理后的包装件进行力学性能测试表明,随着射频处理时间的增加,两种被测材料的拉伸强度、断裂伸长率、杨氏模量均未出现显著变化趋势,表明射频处理不会对这两种塑料薄膜力学性能造成影响。     

热力学数学模型对塑料中化学物向食品模拟液中迁移平衡时分配系数的预测研究

目的分配系数能够直接反映出塑料包装材料中有害化学物向食品迁移的水平,研究分配系数与塑料包装材料、迁移物及食品(模拟物)三者之间的关系有重要意义。方法以Scatchard-Hildebrand统计热力学理论为基础,从热力学平衡角度分析了化学物在包装材料/食品体系中的迁移和分配过程,建立了一个预测化学物迁移平衡时分配系数的热力学数学模型。通过所建立的初级数学模型对聚乙烯薄膜中四种抗氧化剂,即2,6-二叔丁基-4-甲基苯酚(BHT)、二丁基羟基茴香醚(BHA)、Irganox1010和Irganox1076向脂肪类食品模拟物异辛烷迁移平衡时状态进行模拟计算,并与已公开发表的实验数据进行了对比。结果聚乙烯薄膜中四种抗氧剂向异辛烷中迁移平衡的分配系数模拟值与实验值随温度变化趋势一致。结论该热力学模型符合迁移理论,对PE/抗氧剂/脂肪类食品体系分配系数的预测有一定的适用性。     

包装材料对高氧气调包装冷鲜肉品质变化的影响

气调包装能有效延长冷却肉的货架期,但是不同阻隔性的包装材料对冷却肉的保质期影响差异显著,因此选用3种不同阻隔性的包装材料,对冷鲜肉进行高氧气调包装(35% CO2、65% O2),测定冷鲜肉在贮藏期的菌落总数、大肠菌群、色泽、挥发性盐基态氮、汁液流失率和pH值等指标,观察不同阻隔性的材料对冷却肉货架期品质的影响。结果表明：高氧包装条件下,高阻隔材料包装的冷却肉在贮存10d菌落总数已经超标,pH值在贮存期内处于二级鲜肉的范围内;中阻隔包装材料包装的冷却肉菌落总数对数值在保质期内未超过6(lg(CFU/g)),但是肉色保持的较好,感官评价相对较好,但是汁液流失较大;低阻隔包装材料低阻隔性的包装材料菌落变化最大,13d时菌落总数对数值达到6.46(lg(CFU/g)),肉的色泽相对较差,气味和总体可接受性也较差,因此,中阻隔性包装材料效果较好。     

无菌真空热包装生产线中包装材料的探讨

以新鲜冻光鸡为试验原料,采用无菌真空热包装生产工艺,选择铝塑复合膜与PT/PVDC/PE复合膜两种包装材料,在无菌的生产条件下对烧鸡进行趁热抽真空包装,进行对比试验,得出结论,选择PT/PVDC/PE复合膜作为包装材料有一定的优势。     

食品包装PE材料中荧光增白剂迁移规律的分析

以PE塑料薄膜为研究对象,采用高效液相色谱法研究食品包装塑料材料中荧光增白剂在纯水、乙酸、乙醇、植物油4?种不同模拟物中的迁移规律,研究荧光增白剂溶出量与食品接触介质、乙酸质量浓度、乙醇体积分数、浸泡温度以及处理时间等因素的关系。结果表明：纯水基质食品模拟物对香豆素类荧光增白剂有一定溶解性,酸性食品模拟物相比于水模拟物有更强的溶解性,而含醇类食品模拟物和脂肪类食品模拟物对大部分荧光增白剂都具有较好的溶解效果;荧光增白剂的溶出量随着乙酸和乙醇含量的增加而增加;较高的温度对塑料包装材料中荧光增白剂的迁移溶出具有显著影响,并且随着接触时间的延长,塑料包装材料中的荧光增白剂向食品中迁移的可能性也不断增大。     

Use of Tenax® films to demonstrate the migration of chemical contaminants from cardboard into dry food

ABSTRACT

Contaminants in food packaging are a challenge of our time since the packaging material itself has been found to represent a source of food contamination through the migration of substances from it. Before first use, packaging materials destined for the packaging of dry foods can be evaluated by performing migration experiments with the simulant for dry foods, Tenax®. This simulant is commercially available as a powder that is more difficult to handle during the migration experiments. This paper reports the development of a Tenax film. The film can be applied to the cardboard surface to conduct the migration test. After the migration is completed, the film can be easily extracted to determine the concentration of the contaminants in the film. Finally, the performance of the Tenax film was compared with the conventional Tenax powder for the evaluation of 15 model migrants.     

Influence of frozen storage and packaging on oxidative stability and texture of bread produced by different processes

The influence of packaging barrier properties and frozen storage on phenolic and phytosterol content, oxidative stability and crumb texture of frozen dough, part-baked and fully baked frozen bread was investigated in comparison to conventionally produced bread. Samples were stored either in blue coloured high density polyethylene (PE-HD) or transparent polyester-polyethylene-ethylene-vinyl alcohol copolymer (PET-PE/EVAL/PE) pouches for 22 days at −18 °C. Packaging materials were different in oxygen permeability: 3.67 cm³m⁻²day⁻¹ bar⁻¹ for PET-PE/EVAL/PE and 2080 cm³m⁻²day⁻¹ bar⁻¹ for PE-HD material, which did not significantly change during storage. Total phenolic content and oxidative stability of bread samples decreased during storage depending on the process. Frozen dough bread had the lowest phenolics decrease and the highest oxidative stability. Total phenolic content and oxidative stability of frozen breads during 8 days were similar to conventional bread. The phenolics reduction was higher for samples stored in PET-PE/EVAL/PE laminate than in PE-HD packaging. Total sterol content did not significantly change during bread storage in investigated packaging and did not contribute to the oxidation. Bread firmness was affected only by the process and not by the storage time and packaging material.     

Overall migration from commercial coextruded food packaging multilayer films and plastics containers into official EU food simulants

The overall migration from a wide range of commercial five-layer coextruded packaging films into aqueous food simulants (distilled water, 3% aqueous acetic acid) and alternative fatty food simulant (iso-octane) was studied. The overall migration from commercial plastics cups (PS, HIPS, and PP) used for ice-cream or yogurt packaging into distilled water and 3% aqueous acetic acid was also studied. Test conditions for packaging material/food simulant contact and method of overall migration analysis were according to the EU directives and CEN-standards. The results showed that for all tested five-layer films and plastics (PS, HIPS, and PP) cups values of overall migration into aqueous simulants (0.11-0.79 mg/dm², 2.3-15.9 mg/l) and (<0.10-0.41 mg/dm², <0.80-3.1 mg/l) were significantly lower than the upper limit (10 mg/dm²) for overall migration from plastic packaging materials and articles into food and food simulants set by the EU Directive 90/128/EEC and their revisions. The overall migration values from five-layer materials into iso-octane were significantly higher (0.94-8.23 mg/dm², 18.8-164.7 mg/l) than the above values but are still lower than the upper limit for overall migration. Global migration values of five-layer films into aqueous food simulants seems to be independent of material thickness. In contrast, overall migration into iso-octane increases with film thickness.