Mathematical model to describe the release of an antimicrobial agent from an active package constituted by carvacrol in a hydrophilic EVOH coating on a PP film

Antimicrobial active packaging is a novel technology in which a chemical compound (or mixture) is purposely incorporated into a packaging material to be released into the food to protect it from deterioration. The effectiveness of an antimicrobial package is strongly related to the balance between the controlled release of the active compound and microbial growth kinetics. This work characterizes and models the release of carvacrol from an EVOH coating on a PP film which can be employed as an active packaging system. The kinetics and extent of carvacrol mass transport within the packaging components were fully characterized as a function of relative humidity. As expected, water uptake by the EVOH coating acts as a triggering mechanism for activity. The partition equilibrium for carvacrol in the complex film largely favors (10,000-fold) the EVOH layer in dry conditions, although in humid conditions the solubility in both polymers is very close (4-fold). Kinetically, the presence of humidity increases the value of D for carvacrol in EVOH from 3 · 10⁻¹⁹ m²/s in dry conditions to 3 · 10⁻¹⁵ m²/s in a wet environment.After the experimental characterization of carvacrol transport, the efficiency of the release of carvacrol was estimated with a novel mathematical model based on the finite element method and successfully compared with the evolution of carvacrol concentration in a real packaging system. The model developed can be employed in the optimization of package design in order to ensure the maintenance of a specific concentration of the active agent in the headspace, high enough to prevent potential growth of a particular foodborne spoiling or pathogenic microorganism on the preserved foodstuffs. This model could easily be extended to similar packaging systems as long as an inventory of experimental data for all the parameters and coefficients involved is available, sufficiently complete to fulfill all the mathematical requirements demanded by the model.     

可食性活性涂膜在鲜切果蔬保鲜中的应用

可食性涂膜是一种由天然可食性材料制成的选择透过性薄膜,具有调节果蔬内部气体交换、减少水分损失、降低腐烂率及延长货架期的特性,在果蔬包装及保鲜领域中已引起广泛关注。鲜切果蔬具有新鲜、方便、快捷等特点,已在全球范围内广泛供应餐饮业及零售业。可食性涂膜作为多种食品添加剂的载体常应用于生鲜产品中,且将活性添加剂与可食性涂膜结合可以延长鲜切果蔬的货架期,提高果蔬品质,减少果蔬表面致腐及致病菌增长的风险。可食性活性涂膜将作为一种绿色、安全、营养的保鲜技术,并将应用于鲜切果蔬保鲜领域的研究。本文综述了可食性涂膜的分类及其添加的抗菌剂、抗氧化剂、塑形剂、营养素等活性成分在鲜切果蔬保鲜中的应用,旨在开发用于鲜切果蔬保鲜的功能性可食性涂膜。     

Application of Gelidium corneum Edible Films Containing Carvacrol for Ham Packages

ABSTRACT:  We prepared an edible film of  Gelidium corneum  (GC) containing carvacrol as an antimicrobial and antioxidative agent. The GC film containing carvacrol significantly decreased the WVP, while TS and %E values were increased, compared to the film without carvacrol. Increasing amounts of an antimicrobial agent increased antimicrobial activity against  Escherichia coli  O157:H7 and  Listeria monocytogenes . Application of the film to ham packaging successfully inhibited the microbial growth and lipid oxidation of ham during storage. Our results indicate that GC film can be a useful edible packaging material for food products, and the incorporation of carvacrol in the GC film may extend the shelf life.     

Temperature-sensitive polyurethane (TSPU) film incorporated with carvacrol and cinnamyl aldehyde: antimicrobial activity,sustained release kinetics and potential use as food packaging for Cantonese-style moon cake

Temperature-sensitive polyurethane (TSPU) films incorporated with carvacrol and cinnamyl aldehyde were prepared for the potential use of food packaging. The antimicrobial properties and sustained release kinetics of carvacrol and cinnamyl aldehyde in TSPU film were investigated. Results indicated that cinnamyl aldehyde and carvacrol had favourable antimicrobial properties at relatively low addition ratio. The diffusion and release of carvacrol were linearly related to temperature and its addition ratio. The release rates of carvacrol from TSPU film increased from 0.6% to 2.2% with the increase of addition ratio and temperature. The first-order kinetic equation could be used to describe its diffusion and sustained release process. TSPU films could significantly prolong the shelf life of Cantonese-style moon cakes by effectively inhibiting microbial growth and decreasing lipid oxidation comparing with commonly used polyethylene food packaging. Results obtained in the present work can provide technical guide of sustained release food packaging films with antimicrobial properties.     

Improving packaged food quality and safety. Part 1: Synchrotron X-ray analysis

The objective was to demonstrate, as an example of an application, the potential of synchrotron X-ray analysis to detect morphological alterations that can occur in barrier packaging materials and structures. These changes can affect the packaging barrier characteristics when conventional food preservation treatments are applied to packaged food. The paper presents the results of a number of experiments where time-resolved combined wide-angle X-ray scattering and small-angle X-ray scattering analysis as a function of temperature and humidity were applied to ethylene-vinyl alcohol co-polymers (EVOH), polypropylene (PP)/EVOH/PP structures, aliphatic polyketone terpolymer (PK) and amorphous polyamide (aPA) materials. A comparison between conventional retorting and high-pressure processing treatments in terms of morphologic alterations are also presented for EVOH. The impact of retorting on the EVOH structure contrasts with the good behaviour of the PK during this treatment and with that of aPA. However, no significant structural changes were observed by wide-angle X-ray scattering in the EVOH structures after high-pressure processing treatment. These structural observations have also been correlated with oxygen permeability measurements that are of importance when guaranteeing the intended levels of safety and quality of packaged food.     

The influence of electron beam irradiation of antimicrobial-coated LDPE/polyamide films on antimicrobial activity and film properties

We evaluated the effects of ionizing radiation (1-3 kGy) and incorporation of antimicrobials on the functional properties of low-density polyethylene (LDPE)/polyamide films. We established the antimicrobial effectiveness of several coatings of FDA-approved antimicrobial compounds including sorbic acid, carvacrol, trans-cinnamaldehyde, thymol and rosemary oleoresin using selected food pathogen surrogates. The antimicrobial coatings were applied to one side of the LDPE films and dried. Films were irradiated using a 10 MeV linear electron beam accelerator at room temperature. All films showed inhibition zones in an agar diffusion test against Listeria innocua ATCC 33090 and Escherichia coli ATCC 884. In the liquid culture test, the antimicrobials significantly (p?0.05) reduced the specific growth rate of L. innocua by 3.8-8.5%, and decreased final cell concentration of both strains by 5.7-14.6% and 7.2-16.8%, respectively. All active compounds retained the antimicrobial activity when exposed to 1-3 kGy. Neither the presence of active compound nor dose affected the film's tensile strength and toughness. Additionally, films became more ductile and had improved moisture barrier functionality. Film's oxygen permeability was not affected by either treatment. Results are an initial step toward the development of self-sterile active packaging materials for use in combination with irradiation treatment of foods.     

Functional Properties of Plasticized Bio-Based Poly(Lactic Acid)_Poly(Hydroxybutyrate) (PLA_PHB) Films for Active Food Packaging

Fully bio-based and biodegradable active films based on poly(lactic acid) (PLA) blended with poly(3-hydroxybutyrate) (PHB) and incorporating lactic acid oligomers (OLA) as plasticizers and carvacrol as active agent were extruded and fully characterized in their functional properties for antimicrobial active packaging. PLA_PHB films showed good barrier to water vapor, while the resistance to oxygen diffusion decreased with the addition of OLA and carvacrol. Their overall migration in aqueous food simulant was determined and no significant changes were observed by the addition of carvacrol and OLA to the PLA_PHB formulations. However, the effect of both additives in fatty food simulant can be considered a positive feature for the potential protection of foodstuff with high fat content. Moreover, the antioxidant and antimicrobial activities of the proposed formulations increased by the presence of carvacrol, with enhanced activity against Staphylococcus aureus if compared to Escherichia coli at short and long incubation times. These results underlined the specific antimicrobial properties of these bio-films suggesting their applicability in active food packaging.     

活性包装薄膜的功能特性表征及对食品保鲜作用的研究进展

本文综述了活性包装薄膜的功能特性表征与对食品保鲜作用的研究进展,归纳总结了薄膜抗菌和抗氧化功能的表征方法,并从这两个方面介绍了薄膜对食品的保鲜作用,旨在为今后的研究提供参考。活性包装薄膜抗菌功能的表征方法主要有抑菌圈法、抑菌率法、微生物生长曲线法和包装食品直接测定法等,抗氧化功能的表征方法主要有自由基清除法、铁离子还原/抗氧化能力法和包装食品直接测定法等。薄膜对食品的保鲜作用主要体现在薄膜对所包装食品中微生物生长的抑制,对脂类、蛋白质氧化进程的减缓以及食品货架期的延长。     

一种双层智能膜的制备及在指示三文鱼新鲜度中的应用

为了提高天然花青素作为新鲜度指示剂在食品包装中的稳定性,本研究将结冷胶和桑葚花青素作为内层膜用于指示三文鱼新鲜度,壳聚糖-聚乙烯醇形成致密隔氧的外层保护膜,通过逐层组装制备食品新鲜度指示膜,并用于三文鱼的新鲜度可视化检测。结果表明：当外层膜中壳聚糖和聚乙烯醇的体积比为1∶1时,双层膜的机械性能最好,其中拉伸强度为40.65 MPa,断裂伸长率为54.36%,膜的水蒸气透过系数最低;扫描电子显微镜结果表明,外层膜壳聚糖和聚乙烯醇的体积比为1∶1时,膜的结构相容性最好,该体系下桑葚花青素稳定性最好。将双层膜用于三文鱼新鲜度指示,在4 ℃贮藏环境下,随着贮藏时间的延长,三文鱼的总挥发性盐基氮含量不断上升,6 d后,总挥发性盐基氮含量大于30 mg/100 g,硫代巴比妥酸反应产物值为0.921 mg/kg,pH值为6.75,且通过肉眼可以直观看到膜的颜色由暗红变为淡紫色,最后变成蓝褐色,鱼肉已经腐败。结论：基于壳聚糖-聚乙烯醇/结冷胶花青素组成的双层膜既可降低花青素氧化作用提高其稳定性,又可用于三文鱼新鲜度指示。     

Development of antimicrobial films for microbiological control of packaged salad

The aim of the present work was to characterize the antimicrobial efficiency of films consisting of PP/EVOH structures with oregano essential oil and citral. Both substances are known for their antimicrobial activity based on their interaction with the cell membrane. The films developed were used to pack minimally processed salads, combining modified atmosphere technology to extend shelf-life and active packaging technology to reduce possible microbiological risks. The antimicrobial activity of the films against the pathogenic microorganisms Escherichia coli, Salmonella enterica and Listeria monocytogenes and natural microflora was investigated "in vitro" and also on the food itself. The effect of release of the antimicrobial agent on the sensory characteristics of the salad was also studied. The results showed that antimicrobial activity reduced spoilage flora on the salad as well as inhibited the growth of pathogens in contaminated salads. This effect was greater against Gram-negative bacteria. Sensory studies showed that the package that was most effective and most accepted by customers was the one containing 5% oregano essential oil.     

Trends in antimicrobial food packaging systems: Emitting sachets and absorbent pads

Active antimicrobial packaging interacts with packaged food and headspace to reduce, retard, or even inhibit the growth of spoilage and pathogenic microorganisms. Sachets and pads are one of the most successful applications of active food packaging. This review discusses recent developments of antimicrobial active packaging focused exclusively on emitting sachets and absorbent pads, including elaboration techniques, characterization methods, and applications for food preservation purposes. Advantages, drawbacks, and future trends are also discussed, as well as the antimicrobial compounds incorporated in emitting sachets and absorbent pads, including ethanol, chlorine dioxide, a variety of plant essential oils and their main active compounds, and nanoparticles.     

Production and characterisation of skate skin gelatin films incorporated with thyme essential oil and their application in chicken tenderloin packaging

In this study, skate skin gelatin (SSG) was used as a new biodegradable film source and a SSG film was prepared. In addition, thyme essential oil (TEO) was incorporated in the SSG film as an antimicrobial agent for the preparation of an antimicrobial film. The tensile strength (TS) of the film decreased, whereas elongation at break (E) increased by the addition of TEO. The SSG film containing TEO showed increased antimicrobial activity against Listeria monocytogenes and Escherichia coli O157:H7 as TEO concentration increased. To apply the SSG film to food packaging, chicken tenderloin samples were wrapped with the film containing 1% TEO. The packaging of chicken tenderloin with the TEO‐containing SSG film inhibited the growth of L. monocytogenes and E. coli O157:H7 compared to the control during storage. Therefore, the SSG film with added TEO has potential as active food packaging to extend the shelf life of chicken tenderloin.     

兔皮明胶/迷迭香酸复合膜在猪肉冷藏保鲜中的应用效果

制备含有不同质量浓度（0、0.3、0.5、0.8 g/L）迷迭香酸（rosmarinic acid,RosA）的兔皮明胶膜,采用明胶膜单独包装和以明胶膜作为内包、聚乙烯（polyethylene,PE）膜为外包两种方式对新鲜猪肉进行包装。结果表明：使用RosA明胶膜包装可有效抑制猪肉在冷藏过程中挥发性盐基氮含量、菌落总数和pH值的上升,并对脂肪氧化有一定抑制作用,且保鲜效果与实验选择范围内RosA的质量浓度呈正相关。0.8 g/L RosA明胶膜包装组与单纯PE包装组可分别使猪肉的货架期由4 d（对照组）延长至8 d和6 d,PE/0.8 g/L RosA明胶膜包装组则可将货架期延长至10 d。此外,通过测定色差、硬度等指标以及直观观察猪肉颜色,发现贮藏过程中PE/RosA明胶膜包装组较单独RosA明胶膜包装组可以更好地保持猪肉质构品质和色泽。因此,PE/RosA明胶膜可以作为一种有效的活性包装方式,用于肉类的冷藏保鲜。     

Combined effect of high pressure treatment and anti-microbial bio-sourced materials on microorganisms' growth in model food during storage

Antimicrobial bio-sourced films based on poly(lactic acid) containing either carvacrol or allyl isothiocyanate (AITC) were prepared and their antimicrobial properties were assessed on Botrytis cinerea during storage and after a high pressure (HP) “pasteurisation-like” treatment (up to 800 MPa at ambient temperature). A dry process (extrusion + thermomoulding) was used to shape the material. The high temperature encountered during film processing dramatically decreased the carvacrol and AITC content in the film, leading to a less efficient antimicrobial activity. The use of β-cyclodextrin (β-CD) to encapsulate the active compounds before film processing proved to be efficient to protect the AITC against thermal degradation and to control its release from the films during its use. PLA-based films containing either AITC or β-CD encapsulated AITC showed a significant activity against B. cinerea. An effective combination between the antimicrobial activity of AITC-based films and the high pressure treatment was observed on a model food system (PDA) inoculated with N × 10⁴ (N ~ 1–9) conidia of B. cinerea. An HP treatment of only 300 MPa associated with an antimicrobial PLA/β-CD system providing an initial quantity of active agents equivalent to 4 mg of AITC/L of air (i.e. almost 2 folds lower than the minimal inhibition concentration of the active packaging used alone, which was determined to be equal to 10 mg/L of air in the same conditions) was found more efficient (total inhibition of B. cinerea growth during 10 days) than an 800 MPa HP treatment used alone (increase of the lag phase growth of 3.3 days).

Industrial relevance

The consumer demand for “fresh like” product containing reduced amount of preservatives without compromising human and environmental safety needs the development of new preservation strategies. As a consequence, the concept of “hurdle technologies” has risen up. The combined effect of HP treatment and volatile antimicrobial packaging allowed the use of lower individual treatment intensities to inhibit B. cinerea growth. Combining such “hurdles” is of relevance in the context of development of low-cost and eco-friendly food technologies.     

Controlled release of thymol from zein based film

Active packaging materials, able to release antimicrobial compounds into foodstuffs, can be used in order to inhibit or slow down bacterial growth during storage. Zein-based mono and multilayer films were loaded with spelt bran and thymol (35% w/w) to obtain edible composite polymeric materials. Various composite systems were developed to control the release of thymol. In particular, the thickness of the layers and the biodegradable fibres amount were varied. Results highlight that thymol release rate decreased with the increase of the film thickness for both mono and multilayer films, without spelt bran addition. Conversely, a significant increase of thymol release rate with the increase of the bran concentration is recorded for both mono and multilayer films.Industrial relevanceIn recent years, food safety is an important area of concern to the food industry. This fact requires packaging to be an integral part of the preservation concept. Consequently additional antimicrobial activity from the packaging material can aid in shelf life extension. The present work is focused on the development of controlled release systems based on zein incorporated with an active compound, thymol and natural fibres. Release rate of thymol from the developed mono and multilayer films, as affected by layers thickness and fibres amount, was evaluated.     

芳香精油在食品保藏中的应用性研究进展

芳香精油是重要的植物次生代谢物,药食应用历史悠久,因其多方面的生物活性,已引起人们对其在食品保藏领域替代化学防腐剂的极大兴趣。文中概述了芳香精油及其成分在采后果蔬、预切果蔬片、肉制品、乳制品和水产品等食品保鲜和贮藏领域中应用性和安全性研究的最新研究进展。许多研究表明,牛至、丁香、罗勒、胡荽、肉桂、百里香、薄荷、迷迭香、芥茉、芫荽、红根草等芳香精油以及丁子香酚、香芹酚、肉桂酸、己醛、草蒿脑、麝香草酚、香芹酮、肉桂醛、柠檬醛、香叶醇等单体成分具有优良的抗食源性腐败菌和致病菌活性。通过与食品生产前处理工艺、气调包装、配方优化等手段的结合,一些芳香精油及其成分显示出天然食品保藏剂良好的商用价值。     

Retention of α-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) in contact with foodstuffs and food-simulating liquids

Alpha-tocopherol occurs as a natural antioxidant in many foods and has also found use as a stabiliser in polymeric packaging materials. During storage of a food in contact with a plastic material, α-tocopherol may be released from the packaging material and transferred into the food. An active packaging application with the transfer of a substance, such as an antioxidant, from a packaging material to a food may help to prolong the shelf-life of the food. In this study, the retention of α-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) was investigated for contact with liquid foods with different fat contents and food simulants with different ethanol contents. The PP film exhibited excellent retention of α-tocopherol when in contact with all media, whereas some losses were observed from the LDPE film. A number of factors including fat, alcohol and organic acid contents of the various foodstuffs seemed to influence the loss of α-tocopherol from the LDPE film. © 1999 Society of Chemical Industry     

Encapsulation of coriander essential oil in cyclodextrin nanosponges: A new strategy to promote its use in controlled-release active packaging

In this work, we exploit the antimicrobial properties of coriander essential oil (CEO) incorporated in dextrin-derived nanosponges to create a stable controlled release system. Nanosponges (CD-NS) were loaded with CEO, characterized by means of scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction (XRD), and tested for their antimicrobial activity against foodborne pathogens. A head-space-solid phase microextraction coupled to gas chromatography (HS-SPME-GC–MS) method to assess CEO five major compounds was successfully validated. CEO loading was dependent on solvent and CD-NS choice. Additionally, CEO incorporation in CD-NS increased its crystallinity. While β-CD-NS and HP-β-CD:β-CD-NS incorporated higher CEO amounts than α-NS, the later proved more effective regarding their antimicrobial activity. CEO-α-CD-NS and CEO-HP-β-CD:β-CD-NS revealed a predominant bactericidal activity, CEO-β-CD-NS only exhibited a bacteriostatic action. We describe, for the first time, the incorporation of whole EOs in CD-NS and their ability to provide a controlled oil release, especially in the cases of β-derived-CD-NS, while inhibiting bacterial growth, creating a potential new strategy to overcome the poor efficacy of current antimicrobial food packaging.Industrial relevanceThe manufacturing of antimicrobial food packages is still hindered by the problems posed by its lack of efficiency and poor compound stability. The fact that the cyclodextrin nanosponges synthetized in this work can provide a controlled release of antimicrobial active agent, in this case, coriander essential oil while preserving this compound's antimicrobial activity against foodborne pathogens can open the doors for its use in antimicrobial food packaging films. Furthermore, given that cyclodextrin nanosponges are stable at temperatures over 200 °C, gives the packaging industry the opportunity of incorporating this technology during the extrusion process of film making, making the process of active packaging materials cheaper, faster and more readily scalable.     

魔芋葡甘聚糖基活性纳米复合膜的构建及性能研究

目的 对魔芋葡甘聚糖(konjac glucomannan, KGM)薄膜进行改良。方法 以KGM为基质, 棉花纤维素纳米晶须(cellulose nanocrystals, CNC)作为增强剂, 马尾藻多酚(phlorotannins from Sargassum, PS)为抗菌抗氧化剂, 通过物理性能、自由基清除能力和抗菌性检测, 筛选KGM/CNC/PS活性纳米复合膜包装材料。该包装材料运用在鲜猪肉保鲜上时, 以菌落总数(total bacterial count, TBC)、总挥发性盐基氮(total volatile base nitrogen, TVB-N)、硫代巴比妥酸反应物(thiobarbituric acid reactive substances, TBARS)、pH等指标判断鲜猪肉腐败变质程度。结果 当质量比KGM:CNC:PS=100:9:9.81 (KCP-9)时, KGM/CNC/PS活性纳米复合膜的热稳定性、力学性能、水蒸气阻隔性能相对其他比例的复合膜显著提高, KGM:CNC:PS=100:9:18.53 (KCP-17)时, 抗氧化和抗菌性能最佳, 后者运用在鲜猪肉上时, TBC、TVB-N、TBARS、pH等指标明显优于对照组中不使用任何保鲜剂的猪肉, 可延缓鲜猪肉腐败变质速度, 延长其货架期。结论 当KGM:CNC:PS=100:9:18.53 (KCP-17)时, KGM/CNC/PS活性纳米复合膜包装材料具有良好的抗氧化和抗菌性, 在食品保鲜领域具有潜在的应用前景, 本研究可为提高食品包装材料机械性能、抗菌性和抗氧化能力研究提供参考。     

留兰香环糊精抑菌缓释功能改性对聚丙烯基薄膜包装性能及乳化香肠货架期的影响

以聚丙烯（polypropylene,PP）为基材,留兰香（spearmint,S）提取物为抑菌物质,β-环糊精 （β-cyclodextrin,β-CD）为缓释层,采用挤出吹塑制备PP型、S/PP型、S-β-CD/PP型薄膜包装袋,用于包装乳化香 肠,并以薄膜的厚度、力学性能、透光率、水蒸气透过率、抑菌性能及25 ℃贮藏环境下香肠的色泽、pH值、硫代 巴比妥酸含量、菌落总数等作为指标,评价功能性抗菌缓释薄膜的保鲜效果及乳化香肠的货架期。结果表明：β-CD 作为包埋介质可以极大地减少薄膜加工过程中温度对留兰香物质有效成分的破坏;质量分数1% S-β-CD/PP薄膜可以持 续并稳定地起到抑菌效果,延长乳化香肠货架期至50 d。本实验结果为肉制品包装材料研究提供了新的思路。