Effect of high‐pressure processing on the permeance of selected high‐barrier laminated films

This study investigated the effects of high pressure processing (HPP) on the barrier properties of eight multilayer films. Pouches made from these films were filled with distilled water, sealed and then pressure processed at 600 and 800 MPa for 5, 10 and 20 min at 45°C. Controls were similarly prepared but exposed to atmospheric pressure. After processing, all pouches were dried and their oxygen, carbon dioxide and water vapour permeance determined. Films used in this study were PET/SiO_x /LDPE, PET/Al₂O₃/LDPE, PET/PVDC/nylon/HDPE/PE, PE/nylon/EVOH/PE, PE/nylon/PE, metallized‐PET/EVA/LLDPE, PP/nylon/PP and PET/PVDC/EVA. Results showed that metallized PET was most severely affected by HPP, as its permeance values for oxygen, carbon dioxide and water increased as much as 150%. Copyright © 2000 John Wiley & Sons, Ltd.     

Effect of high‐pressure food processing on the mass transfer properties of selected packaging materials

The effect of high‐pressure processing (HPP) on the total migration into distilled water and olive oil and on the barrier properties of four complex packaging materials were evaluated. The films were polyethylene/ethylene‐vinyl‐alcohol/polyethylene (PE/EVOH/PE), metallized polyester/polyethylene, polyester/polyethylene (PET/PE), and polypropylene‐SiOx (PPSiOx). Pouches made from these films were filled with food simulants, sealed and then processed at a pressure of 400 MPa for 30 min, at 20 or 60°C. Pouches kept at atmospheric pressure were used as controls. Prior to and after treatment, all films were evaluated for their barrier properties (oxygen transmission rate and water vapour transmission rate) and ‘Total’ migration into the two food simulants. In the case of water as the food stimulant, a low ‘Total’ migration was observed and even a lower one after the HPP treatment. In the case of oil as the food simulant, a higher ‘Total’ migration was found compared to the control as a result of damage to the structures during the HPP treatment. The gas permeability of the films increased after the HPP, compared to the control, due to damages in the structure caused during the treatment. The PET/PE film presented minimum changes in properties after HPP. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of high‐pressure food processing on the sorption behaviour of selected packaging materials

The sorption behaviour and flavour‐scalping potential of selected packaging films in contact with food simulant liquids (FSLs) (ethanol and acetic acid solutions) were evaluated after high‐pressure processing (HPP). The films used were monolayer polypropylene (PP), a multilayer (polyethylene/nylon/ethylene vinyl alcohol/polyethylene: PE/nylon/EVOH/PE), film and a metallized (polyethylene terephthalate/ethylene–vinyl acetate/linear low‐density polyethylene: metallized PET/EVA/LLDPE) material. D‐limonene was used as the sorbate and was added to each of the FSLs. After HPP treatment at 800 MPa, 10 min, 60°C, the amount of D‐limonene sorbed by the packaging materials and the amount remaining in the FSL was measured. Untreated controls (1 atm, 60°C and 40°C) were also prepared. Extraction of the D‐limonene from the films was performed using a purge/trap method. D‐limonene was quantified in both the films and the FSL, using gas chromatography (GC). The results showed that D‐limonene concentration, in both the films and the food simulants, was not significantly affected by HPP, except for the metallized PET/EVA/LLDPE. Significant differences in D‐limonene sorption were found in comparison with the control pouches. The results also showed that changes in temperature significantly affected the sorption behaviour of all films. Copyright © 2004 John Wiley & Sons, Ltd.     

包装材料对肉类食品胀袋问题的影响与分析

目的 比较分析不同种类包装材料的性能差异对所包装肉类食品胀袋问题的影响。方法 以常见的用于包装烧鸡的PA/Al/CPP、BOPA/LDPE,包装猪蹄的PET/PA/CPP、PET/PA/Al/CPP,包装肉肠的PVDC共挤膜、BOPP/PVDC/PE等6种材料为试验样品,分别测试其揉搓前后氧气透过量、拉伸性能、抗穿刺性能、热封强度、密封性能。结果 样品阻隔性由高到低依次为PET/PA/Al/CPP、PA/Al/CPP、PVDC共挤膜、BOPP/PVDC/PE、PET/PA/CPP、BOPA/LDPE;揉搓后PET/PA/Al/CPP阻隔性仍较高,PA/Al/CPP耐揉搓性差,出现贯穿性针孔,揉搓前后BOPA/LDPE、PET/PA/CPP的阻隔性相差不大;BOPP/PVDC/PE拉伸性能较差,横向断裂伸长率仅为28.4%,且热封强度低,其余样品的拉伸性能、抗穿刺性能、热封强度均较好;PA/Al/CPP,BOPP/PVDC/PE成品包装分别在袋体折皱处、袋体与热封口处漏气,其余样品均未漏气。结论 耐揉搓性差、拉伸性能差及热封强度低分别是烧鸡PA/Al/CPP包装、肉肠BOPP/PVDC/PE包装发生胀袋的主要原因;阻氧性偏低易导致由BOPA/LDPE,PET/PA/CPP,PVDC 5层共挤膜包装的烧鸡、猪蹄、肉肠在长时间存储时缓慢胀袋。上述样品存在的问题主要与材质结构、铝箔层质量、材料生产及热封工艺有关。     

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.     

High‐pressure processing effects on the mechanical,barrier and mass transfer properties of food packaging flexible structures: a critical review

Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Role of package headspace on multilayer films subjected to high hydrostatic pressure

The objective of this study was to systematically examine the effect of high‐pressure processing and package headspace on package integrity and properties. Working pressures were 400 and 600 MPa, and starting vessel temperatures were 30°C, 60°C, and 90°C. Coextruded and laminated multilayers packaging films were studied: film A: (PA/EVOH/PP) and film B: (PET‐AlO_x‐OC/PA6/PP), respectively. The films were made into pouches (0.05 m × 0.10 m) and filled with 30‐mL water as a model food. Various headspace volumes (0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30‐cc air/mL H₂O) were introduced into the packaging before processing. Imaging was used to quantify defects such as the formation of white spots on the package surface and delamination of film layers. The results showed that the headspace level and processing initial temperature had a greater effect than the operating pressure on visual defects. The package with 0% headspace did not show any physical damage to the tested films. Furthermore, thermal and mechanical analyses showed that the coextruded film A had better resistance to testing conditions than the laminated structure of film B. The X‐ray diffraction results showed that film B had more defects than film A that altered the crystalline structure. Visual observation revealed white spots and delamination in the inside layer (PP) in both films. The same processing conditions affected the oxygen and water vapour transmission rates of film B more than film A. This work provides a basic guideline to select the right headspace for a given type of packaged food whenever heat and pressure are used simultaneously.     

Evaluation of a bio‐coating as a solution to improve barrier,friction and optical properties of plastic films

The present research dealt with evaluating barrier, friction and optical properties of three different plastic films after deposition of a gelatin‐based bio‐coating. The composite films showed improved barrier properties against oxygen and UV radiation. The oxygen transmission rate decreased in the order of 73% for oriented polypropylene (OPP), 56% for low‐density polyethylene (LDPE) and 40% for polyethylene terephthalate (PET). The increased UV barrier characteristics ranged from 20% for OPP to 12% for both LDPE and PET. Static and kinetic coefficients of friction significantly decreased both in the film‐to‐film and in the film‐to‐metal tests, leading to a desirable value for many applications. However, bio‐coated films showed lower optical performances in terms of transparency and haze. Transparency decreased mainly for LDPE (36%), whereas the haze index increased especially for OPP (85%). Non‐significant differences were observed as far as the water vapour permeability was concerned, except for a slight reduction for PET (from 15.78 to 13.53 cm³/m²/day at 23°C and 90% of relative humidity), suggesting that non‐meaningful effects arose from the addition of a hydrophobic component in the original formulation. Finally, the solubility of the coating in water was around 25% for all the three plastic substrates. The obtained data suggest that the lipid protein coating tested in this study, in spite of its great potential for enhancing some characteristics of plastic packaging films, still exhibits negative aspects which necessitate further improvement. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of Pasteurization and Retort Processing on Spectral Characteristics,Morphological, Thermal,Physico‐Mechanical,Barrier and Optical Properties of Nylon‐Based Food Packaging Materials

The effect of pasteurization and retort processing on spectral, morphological, thermal, physico‐mechanical, barrier and optical properties of three different packaging materials viz., PP/N6/PP, PET/N6/cPP and SiO_x‐PET/N6/cPP were studied. These packaging materials were packed with distilled water, which acted as a food simulant. Subsequently, these pouches were subjected to different thermal processing conditions such as pasteurization and retort processing. Both the processing techniques found to have retained the mechanical properties of all packaging materials. Water vapour transmission rate (WVTR) and oxygen transmission rate (OTR) of nylon‐based combinations were increased after processing. Gloss found to decrease invariably irrespective of the material and increases with the severity of the treatment. XRD diffractogram shows changes in crystal structure as a result of thermal processing, and SEM analysis shows the crystal fragmentation. Absorption of water by the amide group of nylon 6 was observed, which could be a reason for the increase in OTR and WVTR. Copyright © 2014 John Wiley & Sons, Ltd.     

A mathematical model for the prediction of water vapour transmission rate at different temperature and relative humidity combinations

A simple mathematical procedure for the estimation of water vapour transmission rate under different conditions is presented and discussed. The ASTM dynamic and gravimetric methods were used for measuring the water vapour transmission rate of four thin plastic films (PET 19 μm, PVC 16 μm, EVA 15 μm and LDPE 23 μm) under 38 different conditions of temperature and relative humidity and the corresponding permeance values were drawn. On the basis of the Clausius Clapeyron's relationship between temperature and water vapour pressure, a simple equation was derived for a rapid transformation of water vapour transmission rate data. The mathematical procedure was applied to the data collected for the four thin films and good agreement was found between observed and predicted values for the PET and LDPE films, while for the PVC and EVA films the equation developed led to an overestimate of water vapour transmission at the lower temperatures.     

Mechanical and thermal behaviour of flexible food packaging polymeric films materials under high pressure/temperature treatments

The effect of high‐pressure processing on mechanical and thermal properties of four complex packaging materials (polyethylene/ethylene vinyl alcohol/ polyethylene: PE/EVOH/PE; metallized polyester/polyethylene: PETmet/PE; polyester/polyethylene: PET/PE; polypropylene SiOx recovered: PPSiOx) was studied. Pouches of the different materials containing distilled water or olive oil as food simulants, as well as empty ones, were subjected to 400 MPa for 30 min, at temperatures of 20 or 60°C. Delamination and wrinkling were a general consequence of the high‐pressure processing of multilayer polymeric systems. However, no significant changes were observed regarding the mechanical properties of PE containing laminates after pressurization. PPSiOx underwent significant modifications as SiOx completely broke down. Neither thermal property was affected by pressure, as it was the processing temperature that induced tempering effects on the crystallization behaviour of polymeric components. Only PE/EVOH/PE, when in contact with water as a simulant, presented a decrease in the melting point temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Pumpkin seed oil cake/polyethylene film as new food packaging material,with perspective for packing under modified atmosphere

Biopolymer packaging materials show increasing perspective in food packaging. Main limitation remains their high water sensitivity and poor water vapour barrier properties, compared to non polar materials of synthetic origin like polyethylene. In this paper, biopolymer layer obtained from by‐product of oil industry (pumpkin seed oil cake) was laminated on polyethylene in order to obtain new packaging material that would preferably combine water barrier properties of polyethylene and oxygen barrier properties of biopolymer composite material and perform satisfactory mechanical properties. Obtained two‐layer material showed good barrier properties for water vapour (7–8 g/m² 24h), as well as oxygen (12–45 cm³/m² 24h) and light. In addition, mechanical and water sensitivity tests were performed and results showed that new material inherited biopolymer film water sensitivity and mechanical properties with slight improvement. Measured tensile strength and elongation at break was 2–4 MPa and 150–250% in transversal direction and 6–8 MPa and 100–150% in longitudinal direction. Packing in modified atmosphere assay showed that new material can be used for this purpose with good control of oxygen concentration, while packing under increased concentration of CO₂ could be performed for shorter storage period. New two layer material shows promising properties for sensitive food packing under modified atmosphere conditions with reduced use of synthetic, oil‐based materials.     

几种食品包装用塑料膜阻透性能比较

目的研究不同厚度、不同材质的食品包装用塑料膜透氧量、透湿量的变化情况,为食品包装在阻隔性方面的选材提供依据和指导。方法采用压差法和杯式法分别测试塑料膜的透氧量和透湿量。结果单层塑料膜随厚度的增加,透氧量和透湿量均减小,阻隔性能变好。相同厚度的PE,PET,BOPP,PA这4种单层塑料膜中,PA的透氧量最小,PE的透氧量最大,BOPP的透湿量最小,PA的透湿量最大。复合膜厚度增加,其透氧量、透湿量均减小,但减小幅度逐渐变小。塑塑复合膜外层材料厚度不变时,透氧量、透湿量随总厚度变化不太明显,EVOH塑料复合膜的透氧量值和透湿量值较小,通常在5以下,铝箔塑料复合膜的透氧量值和透湿量值均小于1。结论单层塑料膜PA的氧气阻隔性最好,PE的氧气阻隔性最差,BOPP的水蒸气阻隔性最好,PA的水蒸气阻隔性最差。复合膜中,塑塑复合膜的阻隔性主要取决于外层材料,铝塑复合膜的阻隔性最好,含高阻隔材料EVOH的塑料复合膜的阻隔性比普通塑塑复合膜好,其阻隔性可与铝塑复合膜媲美。     

不同阻隔性包装材料对茶叶儿茶素含量的影响研究

选择了LDPE,BOPP/PE,BOPP/PET/PE,PT/AL/PE和BOPP/AL/PE等5种典型具有代表性的包装材料进行了茶叶贮藏试验,从儿茶素的角度比较了它们的处理效果。结果表明:不同阻隔性(阻气、阻湿、阻光)的包装材料对茶叶的儿茶素含量的影响存在极显著差异(P<0.01),从儿茶素角度来讲,包装材料的处理效果优劣依次为BOPP/AL/PE,BOPP/PET/PE,PT/AL/PE,BOPP/PE和LDPE;同时,茶叶需贮藏在常温或低温、干燥、避光、与氧隔绝的环境下,儿茶素才会相对比较稳定。     

油墨溶剂在食品软包装中的残留及迁移规律

目的研究油墨溶剂在食品软包装材料中的残留及迁移行为,为食品包装生产企业提供安全风险控制方面的参考。方法采用顶空气相色谱-质谱联用(HS-GC-MS)技术,对印刷油墨的挥发性溶剂在食品软包装中的残留进行定性定量分析,以检出率较高的苯类溶剂甲苯、酯类溶剂乙酸丁酯和酮类溶剂丁酮为迁移研究对象,分别以PE,PP,PET/CPP,PET/PE,OPP/CPP,PET/PA/CPP为包装材料,研究油墨溶剂在水性食品模拟液(蒸馏水)、酸性食品模拟液(体积分数为3%的乙酸)、醇性食品模拟液(体积分数为10%的乙醇)和脂肪性模拟液(正己烷)中的迁移残留行为。结果研究表明,印刷后的食品软包装材料中大部分都有苯类、酯类和酮类等有机挥发物的残留,残留溶剂在食品模拟液中迁移量的大小依次为正己烷乙醇(体积分数为10%)乙酸(体积分数为3%)蒸馏水,而且对于不同的包装材料迁移量的大小也不同。结论油墨溶剂在食品软包装材料上的残留和迁移行为,主要与环境温度、食品性质以及包装材料的性能有关。     

植物油类调味品防漏油包装材料及措施探索

目的 寻找合适的植物油调味品包装材料、试验配件,以获取热封压力范围,解决植物油调味品行业实际生产中产品包装漏油问题。方法 采用PA15/PE62,PA15/PE65,PA15/PE55,PET/PET镀铝/PE,PET/Al/PE,PET12/PE38等7种包装材料,在使用自动制袋式填充包装机实际生产环境下进行50,150,300 g等3种规格的清油类底料灌装,并施加30 kg重物进行90 d储存试验,每隔15 d观察包装的封口质量;添加热封压力调节配件,在实际生产中可间接指示热封压力范围,进而探索不同材质的热封压力调节范围。结果 在进行了90 d压力储存后,发现3种规格的样品包装材料漏油率在0~17.95%之间,其中PA15/PE62在50,150,300 g等3种规格下的漏油率均为0,可见该材质在现有生产条件下能够有效缓解漏油现象;该压力配件效果较好,得出2种卷料的热封调节配件调节圈数集中在7.4~6.25圈,7.4~5.75圈。结论 PA15/PE65能有效缓解实际生产中的热封部位断根现象、漏油现象;该压力配件的使用便于生产企业找寻热封压力与热封温度的平衡点,进而缓解漏油现象。     

Evaluating the potential of nanoparticles for controlling zinc stearate release from low‐density polyethylene into food simulants

The present study addressed the effect of polymer nanocomposites with different loading contents of fume silica (nanospheres) and nanoclay (nanosheet) on migration of zinc stearate from packaging materials into food simulants. Specific migration levels of zinc stearate from neat low‐density polyethylene (LDPE) and LDPE/nanocomposites into two food simulants stored at 40°C for 10 days were determined by gas chromatography coupled with flame ionization detector. Differential scanning calorimetry (DSC) analysis showed that incorporation of nanoparticles, especially at 1 wt% loading level of nano silica, noticeably increased degree of crystallinity, which significantly reduced water vapour permeability. Nanocomposites had a lower migration of zinc stearate in comparison with neat polymer. Additionally, results of this study revealed that physical properties of the food simulant had dominant effect on migration of zinc stearate.     

Development and characterization of PET/Fish Gelatin–nanoclay composite/LDPE laminate

A three‐layer laminate film was developed with the following structure: polyethylene terephthalate (PET)/fish gelatin (FG)–nanoclay composite/low‐density polyethylene (LDPE). The FG–nanoclay composite material functioned as the oxygen barrier layer and demonstrated comparable oxygen barrier properties when compared with a similar laminate utilizing ethylene vinyl alcohol as the barrier layer at a relative humidity (RH) of up to 50%. The introduction of nanometer‐sized filler clay into the FG matrix lowered the oxygen permeability (OP) because of the tortuosity effect of the clay particles. In addition, the FG–nanoclay composite film exhibited bond strengths similar to both LDPE and PET. The hydrophilic nature of FG significantly increases OP under high (>50%) RH conditions. However, this new FG laminate film could be a possible alternative for packaging designers desiring a more sustainable packaging material for low‐RH (<50%) applications. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of high‐pressure processing on selected polymeric materials and on the migration of a pressure‐transmitting fluid

This study investigated the migration of 1,2‐propanediol (PG) through selected food packaging films exposed to high‐pressure processing (HPP). Pouches made from these materials were filled with 95% ethanol as a food‐simulating liquid. These packages were then processed using a pilot‐scale high‐pressure food processor at 400, 600 and 827 MPa and 30, 50 and 75°C for 10 min. Controls were processed at similar temperatures and times, but at atmospheric pressure. To investigate any structural changes to these films during HPP, water was used as the food simulant at temperatures of 30, 75, 85, 90 and 95°C and at pressures of 200, 400, 690 and 827 MPa. No detectable PG migration into the polyester/nylon/aluminium (Al) polypropylene (PP) meal‐ready‐to eat (MRE)‐type pouches was observed. PG migration into the nylon/ethylene vinyl alcohol (EVOH)/PE (EVOH) pouches was similar at 30, 50 and 75°C after 10 min under atmospheric pressure. However, PG migration into the EVOH pouches significantly decreased when treated with high pressure at 30, 50 and 75°C. At 75 and 50°C, the PG migration was significantly higher than the amounts detected at 30°C. Visible signs of delamination between the polypropylene (PP) and aluminum (Al) layers were observed in the MRE pouches processed at ≥200 MPa and 90°C for 10 min. This delamination appeared to occur between the PP and Al layers. The differential scanning calorimetric analyses and Fourier transform infrared (FTIR) spectra were similar for the high‐pressure treated pouches when compared to their respective controls. This indicated that there were no HPP‐induced molecular changes to the treated pouches. Results from this study should be useful to HPP users for predicting PG migration trends and in deciding the selection of appropriate packaging materials for use under similar processing conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

超高压杀菌处理对包装材料稳定性的影响

在超高压条件下对PET/AL/PE和PET/VMPET 2种塑料薄膜进行处理,测定不同压强及保压时间对材料拉伸强度、断裂伸长率、热封性能及阻隔性能的影响。结果表明:超高压对2种材料拉伸强度及断裂伸长率均未表现出显著影响,但对PET/VMPET/PE材料的热封强度影响显著;在500 MPa压强下保压时间对2种材料的透湿性能影响显著。