Partition Distribution of Aroma Volatiles from Orange Juice into Selected Polymeric Sealant Films

The sorption of organic volatiles from orange juice by polymeric food contact materials was investigated. Three sealant films were evaluated, a commercial low density polyethylene and two developmental films, an ethylene vinyl alcohol copolymer of high ethylene content and a co-polyester. Samples of the films were immersed in the juice for 24 days at 22°C and the level of sorbed volatiles monitored as a function of time. Three probe compounds (d-limonene, neral and geranial) were selected as being representative of orange juice flavor components. A gas chromatographic technique was developed to quantify the level of probe compounds in juice and films. Results compared favorably to the more traditional bromide-bromate titration method. Sorption of organic volatiles by one of the developmental films (co-polyester) was significantly lower than the others.     

品种和后成熟对NFC苹果浊汁挥发性香气成分的影响

为了探讨果实品种和后成熟度对苹果浊汁风味的影响,采用顶空-固相微萃取结合气相色谱-质谱联用技术,基于多元数据分析手段,非靶向分析了富士、嘎啦、华硕、金冠、澳洲青苹等5个品种,在3个后熟度下制成的NFC苹果浊汁挥发性香气成分差异。结果表明:醇类（2-甲基-1-丁醇、1-己醇等）、醛类（己醛、（E）-2-己烯醛等）和酯类（2-甲基乙酸丁酯等）为苹果浊汁的主要挥发性香气成分。品种和后熟度对苹果汁的特征性挥发性香气成分的含量和组成影响显著。澳洲青苹果汁挥发性香气成分总量少且含量低,醛类是其主要的挥发性香气物质;富士、嘎啦和金冠果汁则表现出相似的香气组分特征,酯类、醛类和醇类物质含量丰富,具有浓郁的香甜水果气味和青草味;华硕苹果汁的挥发性香气成分以醇类和醛类为主,整体具有清淡的香味和生青味。另外,随着不断后熟,不同品种苹果浊汁挥发性香气成分的变化呈现不同趋势。澳洲青苹和富士苹果汁中的香气成分逐渐累积,分别有15和28种挥发性化合物含量显著增加;嘎啦和金冠苹果汁香气物质含量呈现先上升后下降的趋势,在第二个后熟阶段风味最好;用采摘初期华硕苹果原料制成的苹果汁香气最浓郁,但随着不断后熟,挥发性香气含量显著降低。本研究开展的苹果汁风味特性研究,可为苹果浊汁加工的原料选择提供理论基础。     

Interactions of Citrus Flavor Compounds with Polypropylene Films of Varying Crystallinities

Equilibrium sorption levels at 23°C were determined individually for two citrus flavor components (d-limonene and 1-carvone) into ground and unground polypropylene films of different crystallinities. Sorption levels at equilibrium were also determined for a mixture of the two flavor compounds. Aqueous solutions of the flavor compounds (200 ppm carvone and 1000 ppm limonene) were employed. Concentrations of flavors remaining in solution before and after exposure were measured by high performance liquid chromatography (HPLC). Results indicated flavor compound polarity, polymer crystallinity and the presence of other flavor compounds in a mixture influenced sorption behavior.     

基于聚类分析的浓缩苹果汁风味品质分析与评价

通过对浓缩苹果汁主要风味物质进行分析,建立其风味品质的客观评价方法,为生产者合理调整工艺提供参考。分别选取风味较好和风味较差的浓缩苹果汁样品,对其挥发性风味物质、有机酸、氨基酸、糖类等主要风味物质进行分析,采用主成分分析、因子分析综合打分、聚类分析等方法筛选出能够有效区分不同风味品质浓缩苹果汁样品的主要风味化合物。选取12批次浓缩苹果汁样品,检测样品中39种主要挥发性风味物质、14种主要氨基酸、6种主要有机酸以及4种主要的糖类等风味物质。根据因子分析综合打分结果,从29种组合中,筛选出能够区分浓缩苹果汁风味的5种主要风味物质,分别为天冬氨酸、丝氨酸、蛋氨酸、果糖和葡萄糖。利用不同年份的8个批次浓缩苹果汁样品对该结果进行了验证,结果表明,这5种风味物质能够有效区分A、B两类浓缩苹果汁。利用筛选出的5种主要风味物质,能够对浓缩苹果汁风味品质进行客观、准确的判别。     

Degradation of low density polyethylene during extrusion. III. Volatile compounds in extruded films creating off‐flavor

This study was aimed at finding a correlation between the experienced off‐flavor in packaged foods and the presence of specific degradation products in PE packaging films. The possibility to trap degradation products by chemical reactions with scavengers, that is, zeolites and maleic anhydride grafted LLDPE, were investigated. This trapping would prevent the degradation products from migrating to the polymer film surface and further into food in contact with the film. This work concludes that off‐flavor in water packed in LDPE‐films depends on extrusion temperature and the content of oxidation products in the polymer film. At lower extrusion temperatures, reactive additives to the LDPE material could control the release of off‐flavor giving components. Adsorbents, such as zeolites, which are able to adsorb degradation products, are effective also at higher extrusion temperatures. The amount of oxidized degradation products in the films correlated well to the perceived off‐flavor in the packed water. The presence of aldehydes and ketones have a clear impact on the off‐flavor. The best correlation between off‐flavor and oxidized components were found for C₇? C₉ ketones, and aldehydes in the range of C₅ to C₈. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 847–858, 2005     

Changes in Apple Juice Flavor Compounds During Processing

Apple juice flavor fractions were collected at several stages during a commercial process. Replicated experiments were designed to collect samples from untreated pulp, from enzyme treated pulp, after pectinase treatment, after microfiltration (MF), and after pasteurization. Additional juice heating experiments were carried out. Six apple juice flavor compounds were identified based on to retention times and reported studies. The flavor profile changed at the different stages of the production line. Temperatures used (～57.2°C) for enzyme activation and MF tended to increase flavor compounds in apple juice except iso-butyl acetate. The higher temperatures used (～85°C) for pasteurization decreased all flavor compounds except propyl butyrate which increased. Results indicate apple juice may contain heat activated precursors of identified flavor compounds.     

Influence of flavour absorption by food-packaging materials (low-density polyethylene, polycarbonate and polyethylene terephthalate) on taste perception of a model solution and orange juice

The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic films after dark storage at 20°C. Owing to absorption, the amount of flavour compounds in the model solution exposed to LDPE decreased substantially. From the model flavour solution valencene was almost completely absorbed by LDPE, followed to a lesser extent by decanal, hexyl acetate, octanal and nonanone. Less flavour compounds were absorbed from the model solution by PC and PET. In contrast to LDPE, valencene was absorbed in the lowest amounts and decanal in the highest. Limonene was readily absorbed from orange juice by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene, myrcene and decanal. Although the flavour content between controls and polymer-treated samples differed substantially, the loss of flavour compounds due to absorption by LDPE, PC and PET did not influence taste perception of a model solution and orange juice significantly up to 29 days of dark storage at 20°C as determined by triangular taste panel tests.     

Sorption of Flavor Compounds by Low Density Polyethylene Film

The interactions of aldehydes, methyl ketones, methyl esters, sulfur compounds and alkylpyrazines with low density polyethylene (LDPE) were investigated. LDPE film, suspended on a stainless steel support, was immersed in simulated milk ultrafiltrate containing a flavor compound. After shaking the glass bottles containing the solutions and film samples for 24 hr at room temperature (24 ± 2°C), the flavor compound was extracted from both the LDPE samples and the SMUF, and quantitated using gas chromatography. The sorption was: aldehydes (C₇-C₁₀) 11% to 63%, methyl ketones (C₇-C₁₀) 1.5% to 43.0%, methyl esters (C₇-C₉) 6.0% to 42.0%, and sulfur compounds 8.5% to 21%. Insignificant levels of alkylpyrazines were sorbed. For all flavor compound classes, as carbon chain length increased, the quantity of sorbed flavor compounds increased.     

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.     

非浓缩还原(NFC)苹果汁加工过程中糖酸风味组分和呼吸速率的变化

通过测定NFC苹果汁、固酸比以及糖酵解途径、三羧酸循环途径、磷酸戊糖途径、细胞色素途径和交替途径等的呼吸速率的变化,明确NFC苹果汁加工过程中影响糖酸风味品质的关键环节和转化的大致途径,为优化NFC苹果汁生产工艺提供依据。结果表明,NFC苹果汁加工过程中风味品质变化可分为原料到榨汁和灭酶到灌装两个阶段。第一个阶段,可溶性糖中的葡萄糖和山梨醇含量升高了49.12%和20.59%,有机酸中的苹果酸含量升高了8.06%、草酸含量显著降低了7.01%,TCAC呼吸速率升高0.64倍,CP呼吸速率降低0.85倍;第二个阶段,果糖、葡萄糖、苹果酸、草酸含量和固酸比的变化呈正态分布,与EMP途径、TCAC途径和AP途径的呼吸速率变化相关。因此,各加工环节对于果汁糖酸风味组分和呼吸速率的影响是不同的,热处理是NFC苹果汁加工过程中风味品质调控关键环节,应加强调节该环节果汁中心代谢酶促反应以优化糖酸风味品质。     

Physical and antibacterial properties of edible films formulated with apple skin polyphenols

Fruit and vegetable skins have polyphenolic compounds, terpenes, and phenols with antimicrobial and antioxidant activity. These flavoring plant essential oil components are generally regarded as safe. Edible films made from fruits or vegetables containing apple skin polyphenols have the potential to be used commercially to protect food against contamination by pathogenic bacteria. The main objective of this study was to evaluate physical properties as well as antimicrobial activities against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica of apple skin polyphenols at 0% to 10% (w/w) concentrations in apple puree film-forming solutions formulated into edible films. Commercial apple skin polyphenol powder had a water activity of 0.44 and high total soluble phenolic compounds and antioxidant capacity (995.3 mg chlorogenic acid/100 g and 14.4 mg Trolox/g, respectively). Antimicrobial activities of edible film containing apple skin polyphenols were determined by the overlay method. Apple edible film with apple skin polyphenols was highly effective against L. monocytogenes. The minimum concentration need to inactive L. monocytogenes was 1.5%. However, apple skin polyphenols did not show any antimicrobial effect against E. coli O157:H7 and S. enterica even at 10% level. The presence of apple skin polyphenols reduced water vapor permeability of films. Apple skin polyphenols increased elongation of films and darkened the color of films. The results of the present study show that apple skin polyphenols can be used to prepare apple-based antimicrobial edible films with good physical properties for food applications by direct contact.     

Degradation of low density polyethylene during extrusion. IV. Off‐flavor compounds in extruded films of stabilized LDPE

This study was aimed at finding a correlation between the experienced off‐flavor in packed foods and the presence of specific degradation products in LDPE packaging films. The possibility to trap degradation products by chemical reactions with scavengers, i.e., a zeolite additive or antioxidants, was investigated This would prevent degradation products from migrating to the polymer film surface and further into food in contact with the film. It was found that off‐flavor noted in water packed in LDPE films depended on extrusion temperature and exposure time for the melt to oxygen, that is, the parameters that influence the contents of oxidation products that are able to migrate from the polymer film. It was also found that adsorption of oxidative degradation products in a zeolite additive or protection of LDPE by using antioxidants could prevent off‐flavor in the packed product (water). However, the antioxidant should be selected with regard to extrusion temperature because thermal instability in the additive might jeopardize the intended effect. Multifunctional antioxidants seem to provide improved protection, the most effective one evaluated in this work being Irganox E201, i.e., vitamin E. Concentrations of oxidized degradation products are well correlated to the perceived off‐flavor in the packed water. The highest correlation between off‐flavor and oxidized components was found for ketones in the range of C₇ to C₉ and aldehydes in the range of C₆ to C₉. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 583–595, 2005     

Performance of reprocessed multilayer LDPE/nylon-6 film

Multilayer LDPE/nylon-6 films with an overall content of 71 wt% LDPE, 24 wt% nylon-6, and 5 wt% PE-based tie-layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy-to-break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low-density polyethylene) and nylon-6 was retained, whereas in extensively mixed samples, nylon-6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O₂ and H₂O vapor barrier properties, whereas extensively-mixed samples had poor barrier properties. Properties of well-mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon-6 components.     

Influence of apple flavor absorption on physical and mechanical properties of poly(ethylene terephthalate) films

Poly(ethylene terephthalate) (PET) films (280‐μm film thickness), which are used in food packaging, were immersed into 160‐ and 320‐ppm apple flavor solution for 14, 28, and 56 days at 5, 25, and 40°C, respectively. At the end of this period, the changes in the PET films were investigated by measuring the mechanical and physical properties. The mechanical properties were determined by examining changes in the Young's modulus. The changes in the physical properties were investigated by Fourier transform IR spectroscopy and scanning electron microscopy (SEM). The formation of microcracks in the structure of PET films was observed by SEM. According to the results of those investigations, the apple flavor affects PET films, even at very low concentrations and temperatures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1802–1807, 2006     

The effectiveness of hexamethylenetetramine‐incorporated plastic for the active packaging of foods

The feasibility of LDPE films containing 0.2 or 0.5% (w/w) hexamethylenetetramine (HMT) as antimicrobial packaging material to inhibit microbial growth on the surface of foods was investigated. As HMT is allowed in Europe to be used as a preservative under certain conditions, and as it is mentioned on the list of additives notified to the European Commission as substances which may be used in plastics intended in contact with food products, this compound offers good opportunities for the manufacturing of an antimicrobial packaging material. In a first experiment, fresh orange juice was vacuum packaged in LDPE films containing 0, 0.2 and 0.5% (w/w) HMT and stored at 6°C for 39 days. Every day and later every 3 days, packages of orange juice were analysed for yeasts and lactic acid bacteria. The shelf‐life of orange juice, could not be prolonged significantly by packaging into a 0.2% or 0.5% (w/w) HMT‐containing film. In a second experiment, however, packaging of cooked ham in a 0.5% (w/w) containing LDPE film, significantly affected shelf‐life. After 20 days a significant reduction of total aerobic count and lactic acid bacteria was observed. In an additional migration test, it became clear that the level of HMT released into orange juice was close to the specific migration limit of 15 mg CH₂O/kg imposed by the EC. Copyright © 2000 John Wiley & Sons, Ltd.     

Volatile and non-volatile radiolysis products in irradiated multilayer coextruded food-packaging films containing a buried layer of recycled low-density polyethylene.

The effects of gamma-irradiation (5-60 kGy) on radiolysis products and sensory changes of experimental five-layer food-packaging films were determined. Films contained a middle buried layer of recycled low-density polyethylene (LDPE) comprising 25-50% by weight (bw) of the multilayer structure. Respective films containing 100% virgin LDPE as the buried layer were used as controls. Under realistic polymer/food simulant contact conditions during irradiation, a large number of primary and secondary radiolysis products (hydrocarbons, aldehydes, ketones, alcohols, carboxylic acids) were produced. These compounds were detected in the food simulant after contact with all films tested, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food preservation). The type and concentration of radiolysis products increased progressively with increasing dose. Generally, there were no significant differences in radiolysis products between samples containing a buried layer of recycled LDPE and those containing virgin LDPE (all absorbed doses), indicating the good barrier properties of external virgin polymer layers. Volatile and non-volatile compounds produced during irradiation affected the sensory properties of potable water after contact with packaging films. Taste transfer to water was observed mainly at higher doses and was more noticeable for multilayer structures containing recycled LDPE, even though differences were slight.     

Studies on the oxygen barrier and mechanical properties of low density polyethylene/organoclay nanocomposite films in the presence of ethylene vinyl acetate copolymer as a new type of compatibilizer

Nanocomposite films based on low density polyethylene (LDPE), containing of 2, 3, and 4 wt.% organoclay (OC) and ethylene vinyl acetate (EVA) copolymer as a new compatibilizer were prepared and characterized using rheological tests, X-ray diffraction, differential scanning calorimetry, oxygen permeation measurements, and tensile tests. There was no exfoliation or intercalation of the clay layers in the absence of EVA, while an obvious increase in d-spacing was observed when the samples were prepared with EVA present. This issue was reflected in the properties of nanocomposites. The oxygen barrier properties of the LDPE/EVA/OC film were significantly better than those of the LDPE/OC film. The average aspect ratio of clay platelets in nanocomposites was determined from permeability measurements and using Lape–Cussler model. In addition to barrier properties, the LDPE/EVA/OC film also had better elastic modulus than their counterparts without EVA. The modulus reinforcement of nanocomposites was studied using Halpin–Tsai equations, which are universally used for composites reinforced by flake-like or rod-like fillers.     

食品中不同种类风味物质对 LDPE 吸附现象的影响研究

采用GC法测定塑料薄膜LDPE对不同种类风味化合物(己醛、庚醛、乙酸丁酯、乙酸丙酯、戊酮、庚酮、异戊醇、辛醇)的吸附量,研究具有不同官能团和分子结构的风味化合物对薄膜吸附过程的影响。试验结果表明:从官能团角度看,LDPE对醛类的吸附最为明显,酮类、醇类次之,同时LDPE与酯类之间也容易结合;而对于同一类型的物质,即具有相同官能团的风味化合物,LDPE的吸附量会随着分子链中碳原子数量的增加而增大。     

基于SPME-GC-MS分析熏制材料对熏鸡腿挥发性风味物质的影响

为探究果木屑、红茶末、白砂糖3 种不同熏制材料对熏鸡腿挥发性风味物质的影响,应用固相微萃取结合气相色谱-质谱联用仪对其挥发性物质进行分离鉴定,通过计算相对气味活度值确定其主体风味成分。结果表明,从烟熏鸡腿中共鉴定出92 种挥发性物质;糖熏的主体风味物质为2-呋喃甲醛、5-甲基-2-呋喃甲醛等糠醛类化合物;木熏的主体风味物质为愈创木酚、4-甲基愈创木酚、4-乙基愈创木酚、4-乙烯基愈创木酚等酚类物质及2-呋喃甲醛、5-甲基-2-呋喃甲醛等;茶熏的主体风味物质为2,6-二乙基吡嗪等含氮化合物和愈创木酚。呋喃类、酚类、含氮化合物均为典型的烟熏风味物质。     

Anhydrides as antimycotic agents added to polyethylene films for food packaging

Incorporation of free acids or salts of antimycotic food additives, including propionic acid, benzoic acid or sorbic acid, into low-density polyethylene (LDPE) films failed to inhibit mould growth when the films contacted inoculated media. However, LDPE films into which benzoic anhydride was incorporated exhibited antimycotic activity when in contact with media and cheese. Benzoic anhydride, which had been added to LDPE film, was hydrolysed within 5h and detected as benzoic acid in potato dextrose agar (PDA) and cheese after contact with the film. LDPE films, into which 1% benzoic anhydride was incorporated, completely inhibited Rhizopus stolonifer. Penicillium spp., and Aspergillus toxicarius growth on PDA. Lower amounts of anhydride partially inhibited growth by increasing the lag phase and reducing the rate of growth in most cases. LDPE films incorporated with 0.5–2% benzoic anhydride delayed mould growth on cheese. These data suggest that addition of antimycotic agents to LDPE during film manufacture may be a feasible way of controlling surface mould growth in foods such as cheese.