Effects of drying methods and conditions on release characteristics of edible chitosan films enriched with Indian gooseberry extract

The present work was aimed at studying the effects of drying methods and conditions (i.e., ambient drying, hot air drying at 40 °C, vacuum drying and low-pressure superheated steam drying within the temperature range of 70–90 °C at an absolute pressure of 10 kPa), as well as the concentration of Indian gooseberry extract, (added to edible chitosan film-forming solution as a natural antioxidant, at concentrations of 1, 2 and 3/100 g), on the residual total phenolic content (TPC) of the films. The swelling and release behaviour of TPC from the films were also studied. Drying methods and conditions were found to have significant effects on the percentage of residual TPC. The release characteristics, swelling and functional group interaction of the antioxidant films, as assessed by Fourier-transform infrared (FTIR) spectroscopy, were found to be affected by the drying methods and conditions, as well as the concentration of the Indian gooseberry extract.     

Effects of drying methods and plasticizer concentration on some physical and mechanical properties of edible chitosan films

In order to alleviate shortcomings of edible chitosan films, which are rigid and brittle in nature, an idea of using advanced drying methods, in combination with appropriate concentration of plasticizer, to improve the mechanical properties of the films was proposed and tested. Physical (thickness and color) and mechanical (tensile strength and percent elongation) properties of edible chitosan films plasticized at four glycerol concentrations (0%, 25%, 75% and 125% w/w chitosan) and prepared by three drying methods, namely, hot air drying (≈40 °C), vacuum drying and low-pressure superheated steam drying (LPSSD) (90 °C, 10 kPa) were investigated. Dynamic mechanical thermal analysis (DMTA) was used to determine the glass transition temperature to verify the compactness of edible chitosan films. It was found that the drying methods and plasticizer concentration significantly affected the drying time, tensile strength, percent elongation and glass transition temperature of the films. On the other hand, the drying methods and plasticizer concentration did not affect the thickness and final moisture content of the film samples at lower glycerol concentrations. In the cases of vacuum drying and LPSSD, there was a limiting value of plasticizer concentration (25% w/w) beyond which the effect of the plasticizer concentration on the mechanical properties was negligible. In all cases, the color of all tested films was not significantly different.     

Comparison of chitosan and gelatin-based films and application to antimicrobial coatings enriched with grapefruit seed extract for cherry tomato preservation

Food Science and Biotechnology - Bio-based single, composite, and bilayer edible films were developed based on chitosan and gelatin, including grapefruit seed extract (GSE) as an antimicrobial...     

Physical and mechanical properties of chitosan films as affected by drying methods and addition of antimicrobial agent

Incorporation of an antimicrobial agent into a biopolymer matrix not only affects the antimicrobial property, but also the physical, mechanical and barrier properties of the resulted films. In addition to the effect of antimicrobial agent different drying methods that are used to prepare the films should also be considered. The aim of this study was to investigate the combined effects of drying methods, namely, hot air drying and low-pressure superheated steam drying (LPSSD), and addition of a natural antimicrobial agent, namely, galangal extract, at concentrations of 0%, 0.6%, 0.9%, 1.2% and 1.5% (w/w film forming solution) on selected physical properties (thickness, moisture content, color and opacity), mechanical properties (tensile strength and percent elongation), barrier properties (water vapor and oxygen permeabilities), degree of crystallinity and degree of swelling of antimicrobial films prepared from chitosan. X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy as well as dynamic mechanical analysis (DMA) were also performed and their results used to explain the observed combined effects. The combined effects were noted to have a statistically insignificant influence on the moisture content, thickness and water vapor permeability of the films. On the other hand, the combined effects had a statistically significant influence on the color, degree of crystallinity, degree of swelling, tensile strength, percent elongation and oxygen permeability of the films. Only the galangal extract concentration had a statistically significant influence on the film opacity. The DMA patterns and FTIR spectra confirmed the formation of crosslinkage interactions between the galangal extract and chitosan matrix.     

Properties and antimicrobial activity of edible films incorporated with kiam wood (Cotyleobium lanceotatum) extract

The antimicrobial properties of wood extracts are well known; however their application to edible films is limited. In this study, the minimum bactericidal concentration (MBC) of kiam wood extract was established as 300 mg/L at which bacterial growth was completely inhibited. The antimicrobial properties of hydroxypropyl methylcellulose (HPMC) films containing 1-5 fold of MBC of kiam wood extract were tested against Escherichia coli O175:H7, Staphylococcus aureus and Listeria monocytogenes. The edible films containing kiam wood extract exhibited more effective impact on the growth reduction of L. monocytogenes than S. aureus and E. coli (p < 0.05). The use of kiam wood extract at 1 and 2 fold of MBC incorporated into edible HPMC films did not exhibit any antimicrobial activity. However, the inhibitory effect of edible HPMC films containing kiam wood extract was observed at 3, 4 and 5 fold of MBC. The greatest zone of inhibition was observed at 5 fold of MBC incorporated in edible HPMC films. Tensile strength and elongation at break significantly decreased with the incorporation of kiam wood extract, whereas water vapor permeability and film solubility increased. The color of edible films became darker and more reddish-yellowish as well as having a lower transparency as the level of kiam wood extract was increased. Kiam wood extract incorporated in edible film provided the films with a rougher surface than pure edible film. Our results pointed out that the incorporation of kiam wood extract as a natural antibacterial agent has potential for use in extending the shelf life of food products.     

Effects of chitosan on the physicochemical and antimicrobial properties of PLA films

Films based on polylactic acid (PLA) and different amounts of chitosan powder (CH), were prepared by extrusion. The effects of CH particle size (715 and 180 μm) and the amount of chitosan incorporated in the PLA matrix (5% or 10% on PLA basis) were investigated in terms of physicochemical characteristics and antimicrobial activity of the films. The incorporation of CH particles led to less rigid and less stretchable films. Thermal properties of PLA were not affected by chitosan addition. Water vapor permeability of the composite films was higher than pure PLA films. PLA:CH composite showed significant antimicrobial activity against total aerobial and coliform microorganisms, especially when the particle size of CH was reduced.     

Structural properties of films and rheology of film-forming solutions based on chitosan and chitosan-starch blend enriched with murta leaf extract

Chitosan (CH) and chitosan-corn starch (CH-CS) film-forming solutions (FFS) and films, with or without polyphenol-rich aqueous extract from murta (Ugni molinae Turcz) leaves (PEML) were prepared. The impact of the FFS type and PEML, considering pH values of the FFS, on dynamic and steady-shear behavior of FFS, interaction mechanisms of PEML with polymer chains and changes on infrared spectra of films were investigated. Mechanical properties, thickness and color from films were also evaluated.     

干燥温度对壳聚糖-明胶复合膜性能的影响

研究干燥温度对壳聚糖-明胶复合膜性能的影响.通过对复合膜拉伸强度、断裂伸长率、吸水率、透水气率和透光率性能的检测表明,干燥温度对膜的物理性能产生了显著的影响.综合各种指标,在50℃条件下干燥,膜的综合性能最好.     

Characterisation of soy extract processed under different drying methods and extraction conditions

Soybean extract (SE), enriched in soy soluble polysaccharide (SSPS), was evaluated in three different conditions varying in extraction temperature and drying process: SE‐A ?80 °C, freeze‐dried, SE‐B ?80 °C, spray‐dried, SE‐C ?95 °C, spray‐dried. Spray‐dried SE presented lower moisture content, smaller and more uniform particles. In addition, zeta potential showed the same negative surface charge for all extracts showing the prevailing behaviour of SSPS. Moreover, all biopolymers were composed of three main molecular weight (Mw) fractions, but the Mw distribution was different between the three ingredients, reflecting their rheological behaviour in aqueous solution. Higher mean Mw led to enhanced apparent viscosity observed in neutral and acid pH for SE‐A, followed by ‐B and ‐C, respectively. The inverse behaviour was observed for intrinsic viscosity at neutral pH. However, SE‐C showed lower intrinsic viscosity at acid pH, which was attributed to protein–polysaccharide interaction presents in the solution.     

Effects of drying methods and conditions on drying kinetics and quality of Indian gooseberry flake

Vacuum drying and low-pressure superheated steam drying (LPSSD) of Indian gooseberry flake (used to prepare Indian gooseberry tea) were carried out at various drying conditions to monitor the drying kinetics and quality degradation of the product during drying. In terms of drying kinetics, the vacuum drying took shorter time to dry the product than LPSSD at every drying condition. In terms of quality, it was found that only the product subjected to vacuum drying at 75 °C and absolute pressure of 7 kPa had similar level of ascorbic acid retention compared to those samples of LPSSD at every condition. The total color difference of this sample was, however, slightly higher than that of product dried by LPSSD. Nevertheless, since the color changes were not of much concern to the consumers of Indian gooseberry tea, vacuum drying at 75 °C and 7 kPa was proposed as the most favorable condition for drying of Indian gooseberry flake in terms of energy consumption.     

Bioactive edible films for food applications: mechanisms of antimicrobial and antioxidant activity

Abstract

In order to improve the quality of food and to extend their shelf life, a new generation of active edible films is being especially intended after the incorporation of organic acids, enzymes, antimicrobial proteins, phenolic compounds, or other functional ingredients such as probiotics, flavors, vitamins and nutraceuticals. These active compounds have different mechanisms of action related to their structure, their concentration, the nature of micro-organism targeted, the process of encapsulation or incorporation in the biopolymer film-networks. The application of the active films by direct contact or indirect contact via the head space also affects the bioactivity of these compounds. This article critically reviews the published work on active edible-films and their applications for food preservation. The classes of active compounds and their action mechanisms are firstly discussed. Then, an extended overview on their effect on model food (simulants) or on real food during storage was also addressed. Edible films offer two main advantages over the direct incorporation of the antimicrobial or antioxidant agents into the bulk food: 1) to control the diffusion of active compounds at the surface of the food and 2) to reduce the amount of preservatives added in the food.     

壳聚糖/香菇多糖可食性膜的性能研究及表征

采用壳聚糖为主要成膜材料,添加一种生物活性成分香菇多糖,以甘油为增塑剂,采用流延法制备新型的可食性复合膜。测定香菇多糖的含量对膜材料性能的影响,并对复合膜进行结构表征。结果表明,随着香菇多糖含量的增加,复合膜的抗拉强度从24.61MPa增加到32.14MPa、断裂延伸率从15.07%降低到4.57%;水溶性逐渐增加,最高时达7.04%;阻氧性先升高后趋于平稳,在香菇多糖含量为1.0%时最佳,过氧化值低至4.28g/100g;水蒸气透过率先降低后升高,在香菇多糖含量为0.75%时达到最小值0.1322g·mm/(m2·h·k Pa)。红外及XRD分析显示复合膜各组分良好相容。      

Antimicrobial activity and physical properties of chitosan–tapioca starch based edible films and coatings

Antimicrobial activity of edible coating solutions based on chitosan and blends of chitosan–tapioca starch with or without potassium sorbate (KS) addition was studied. The agar well diffusion assay showed an antagonist effect on the efficiency of chitosan against Lactobacillus spp. when KS and/or tapioca starch were present. A salmon slice coating assay showed that the chitosan solution was the best coating since aerobic mesophilic and psychrophilic cell counts were reduced, pH and weight loss remained acceptable throughout refrigerated storage, extending global quality to 6-days. Chitosan–tapioca starch based films reduced Zygosaccharomyces bailii external spoilage in a semisolid product but were not effective against Lactobacillus spp. The results suggest that antibacterial action depended on the application technique, due to the fact that chitosan is more available in a coating solution than in a film matrix. Interactions between chitosan–starch and/or KS could affect film physical properties and the antimicrobial activity of chitosan. The addition of chitosan reduced water vapor permeability and solubility of starch films.     

Effect of chitosan edible coating enriched with lemon verbena extract and essential oil on the shelf life of vacuum rainbow trout (Oncorhynchus mykiss)

In this research, the antioxidant and antibacterial characteristics of the chitosan (CH) coating incorporated with lemon verbena essential oil (LVEO) and extract (LVE) on the quality of the rainbow trout packed by vacuum packaging at 4°C were investigated. Samples evaluated include the following: Control, VP, CH, CH-LVE 2%, CH-LVEO 1%, and CH-LVE 1%-LVEO 0.5% for 16 days at 3 days intervals. All of the samples significantly reduced Psychrotrophic bacteria, total viable counts, Enterobacteriaceae, and H₂S producing bacteria as compared with control during keeping time. Thiobarbituric acid reactive substance, peroxide value, total volatile basic nitrogen, and pH value were detected lower in all of the samples than control. CH incorporated with LVE and LVEO gave an agreeable effect on sensory characteristics. Samples containing CH-LVE 1%-LVEO 0.5% was often in priority by sensory assessors. Generally, LV can be applied as a substitution for chemical preservatives in fish meat.     

Effects of drying conditions on some physical properties of soy protein films

The influence of drying conditions (air temperature and relative humidity) on mechanical properties, solubility in water, and color of two kinds of soy protein isolate film: a commercial one (CSPI) and other obtained under laboratory conditions (LSPI) were evaluated using the response surface methodology (RSM). Soy protein films were prepared by casting using glycerol as plasticizer. The films were dried in a chamber with air circulation under controlled conditions of relative humidity (24%, 30%, 45%, 60%, 66%) and air temperature (34, 40, 55, 70, 76 °C). It was verified that mechanical properties of films made from LSPI and CSPI are influenced in a very different way by the drying conditions due to a diverse initial protein conformation in both materials, as was revealed by DSC and SDS–Page studies. The solubility of the LSPI film was affected by temperature and relative humidity, being lowest (～50%) for films obtained at high RH and temperatures ranging from 45 to 76 °C. For CSPI films, in contrast, solubility did not depend on the drying process and it remained relatively constant (～40%). The optimal drying conditions determined by RSM were: 70 °C and 30% RH for CSPI films and 60 °C and 60% RH for LSPI films. Dried under these conditions, CSPI films presented a higher tensile strength, lower elongation at break, lower solubility and better water and oxygen permeability than LSPI ones.     

可食性降解抗菌保鲜膜的研究进展

食品贮藏过程中微生物引起的腐败是影响食品货架期的最重要的因素之一。为此,作为食品流通领域的重要成员,食品包装材料不仅应具有美观商品、便于运输等优点,对一些包装材料还要求具有抗菌、延长食品货架期的功能,并且本身具有安全性和可食用性,这就推动了人们对食品抗菌保鲜膜领域的研究。本文主要介绍了可食性、可降解性(抗菌)保鲜膜的概念、种类(多糖类、蛋白质类、脂类、复合膜类),抗菌剂的种类(有机抗菌剂、无机抗菌剂、天然抗菌剂、细菌素等);阐述了可食性、可降解抗菌保鲜膜的国内外研究现状;展望了可食性降解抗菌保鲜膜的未来发展趋势。本文期望为抗菌保鲜膜领域的研究提供一些新的思路。     

Physico-mechanical properties of chitosan films with carvacrol and grape seed extract

The physico-mechanical properties of 3 films composed by carvacrol, grape seed extract (GSE) and chitosan in different proportions were studied. The films, prepared by solvent casting technique with the following compositions of the casting solutions in carvacrol, GSE and chitosan: film-1: 9.6 ppm–684 ppm–1.25% w/v, film-2: 60 ppm–400 ppm–1.2% w/v and film-3: 90 ppm–160 ppm–1.24% w/v and were compared to a control (1.25% w/v chitosan) film. Mechanical, structural, barrier and colour properties of the films were evaluated. Film-3 presented the lowest water vapour and carbon dioxide permeabilities (WVP and CO₂P) and tensile strength (TS) values and the highest oxygen permeability (O₂P), whereas film-1 presented the highest water content and the lowest crystallinity, CO₂P, TS and luminosity. These results suggest that in the range studied, carvacrol and GSE affect the film structure and its mechanical properties due to hydrophilic (GSE) and hydrophobic (carvacrol) compounds. This work will help the development of edible films, based on physico-mechanical properties, contributing to food preservation and shelf-life extension.     

3种干燥方法对荞麦干燥特性及品质的影响

以振动远红外干燥、烘箱干燥、薄层干燥3种干燥方法荞麦进行干燥,对比3种干燥方法对荞麦干燥特性及干燥后品质产生的影响。结果表明,在干燥特性方面,振动远红外干燥达到安全水分时间最短,干燥速率最大;薄层干燥所需时间最长,干燥速率最小。在品质分析方面,振动远红外干燥工艺对荞麦的外观品质影响较小,干燥后的荞麦面积收缩率最小,同时蛋白质含量最高(17.02%),但发芽率相较薄层干燥工艺略低;经烘箱干燥后的荞麦样品蛋白质含量最低;其发芽率也最低。薄层干燥后的荞麦面积收缩率最大。在实际生产中,可根据具体情况选择适合的干燥方法。     

鱿鱼骨壳聚糖的抑菌性能研究

研究了鱿鱼骨壳聚糖对食品中常见微生物的抑制作用,以大肠杆菌、金黄色葡萄球菌、啤酒酵母、黑曲霉等为受试菌,研究了2种不同相对分子量的鱿鱼骨壳聚糖(1210、844kD)的抑菌性能,并探讨了壳聚糖抑菌作用的稳定性。结果表明,两种壳聚糖对四种菌都有明显的抑制作用,相应最小抑菌浓度对大肠杆菌为0·02%,对金黄色葡萄球菌、啤酒酵母、黑曲霉均为0·05%,壳聚糖的抑菌作用具有良好的热稳定性。      

Effect of surfactants and drying rate on barrier properties of emulsified edible films

The effects of globule size, nature and concentration of surfactant, and drying duration of water vapour transmission rate and tensile strength of emulsified edible barriers containing methylcellulose and paraffin wax, were measured. of the six surfactants tested, 0.6% purified glycerol monostearate (GMS) produced films with the lowest water vapour transmission rates and the highest mechanical resistance. Longer drying times of film-forming emulsions produced better barrier and mechanical properties. Control of the film forming emulsion stability allowed the reduction of the water vapour transfer rate by an order of magnitude.