Improved water resistance in edible zein films and composites for biodegradable food packaging

Zein, corn prolamine, was dissolved in several organic solvents to make films and their properties were examined. Ethanol with 20% water and acetone with 30% water were found to dissolve zein well and transform it into a transparent flexible film after moderate drying. Both films showed similar breaking strength to that of commercial thin film of polyvinylidene chloride for food use and were digested with proteases. Only the film prepared from acetone solution showed a relatively low water permeability. This water permeation was found to depend strongly on the rate of diffusion. 1,2-Epoxy-3-chloropropane (ECP) was added into the acetone solution to cross-link the zein molecules for the purpose of improving the breaking strength and water-resistant properties of the film. Alpha-chymotrypsin was found to digest the film even after the modification with ECP. However, this cross-linking resulted in little improvement in the water-resistant properties of the film and also reduced its flexibility.     

Development and characterization of cassava starch and soy protein concentrate based edible films

The sensory attributes, mechanical, water vapour permeability (WVP) and solubility properties of cassava starch and soy protein concentrate (SPC)‐based edible films of varying levels of glycerol were studied. Addition of SPC and glycerol up to 30% and 20%, respectively, reduced stickiness and improved colour and appearance of the films. Tensile strength (TS), elastic modulus (EM) and elongation at break (EAB) of films increased, while film solubility (FS) and WVP decreased with SPC and glycerol up to 50% and 20% level, respectively, ranging from 20.33 to 26.94 MPa (TS), 41.33 to 72.76 MPa (EM), 7.90 to 12.28 MPa (EAB), 15.07 to 31.90% (FS) and 2.62 to 4.13 g H₂O mm m^?2 day kPa (WVP). The TS, EAB and WVP were higher for the biofilms than for low‐density polyethylene and cellophane films.     

Characterization and antimicrobial activity of sweetpotato starch-based edible film containing origanum (Thymus capitatus) oil

The objectives of this research were to characterize the mechanical and barrier properties of sweetpotato starch (SPS)-based film (SPSF) and to investigate the antimicrobial activity of SPSF containing origanum oil (OG) against foodborne pathogenic bacteria. The SPSF was fabricated with the SPS extracted from commercial sweetpotato roots. Tensile strength (TS), percent elongation at break (E), and water vapor permeability (WVP) were determined to characterize the SPSF fabricated with selected SPS concentrations, plasticizers, and the concentrations of plasticizers. The agar diffusion assay was used to determine the antimicrobial activity of SPSF containing selective concentrations of OG against Salmonella Enteritidis, Escherichia coli O157:H7, and Listeria monocytogenes. The SPSF fabricated with 2.5% SPS exhibited the greatest TS (4.58 MPa). The TS, E, and WVP of SPSF plasticized with 40% sorbitol exhibited 7.96 MPa, 77.92%, 0.212 ng m/m(2) S Pa, respectively. Therefore, the SPSF fabricated with 2.5% SPS and 40% sorbitol was determined as the optimum film. The antimicrobial activity of the SPSF containing OG increased as the concentration of OG increased. And the SPSF containing OG exhibited greater inhibitory effects against the gram-negative bacteria such as S. Enteritidis and E. coli O157:H7 than the gram-positive L. monocytogenes. The greatest antimicrobial activity was observed against S. Enteritidis when the SPSF containing 2% OG was applied, and the maximum square of zone width was 18.43 mm(2).     

The effect of edible coatings and polymeric packaging films on the quality of minimally processed carrots

Minimally processed carrots have a short shelf‐life because of white blush formation (caused primarily by surface dehydration) and microbiological spoilage (caused mostly by lactic acid bacteria). The use of polymeric packaging films combined with edible coatings might have an additive or synergistic effect to extend the shelf‐life of minimally processed carrots because of the formation of a double barrier to gases and water vapour. A 3 × 3 factorial experiment using a polymeric packaging film of three different levels of permeability and a cellulose‐based edible coating (Nature Seal^®) at different concentrations was conducted on minimally processed carrots to investigate any possible synergistic effect over 12 days of storage at 10 °C. No such effect was found. The polymeric packaging film effectively prevented microbiological growth and spoilage but was unable to control white blush formation. On the other hand, the edible coating partially controlled white blush formation but enhanced microbiological spoilage. The polymeric packaging film functioned primarily as a gas barrier, whereas the edible coating probably functioned as a moisture barrier. White blush formation was found to be the most important shelf‐life determinant for minimally processed carrots. Copyright © 2003 Society of Chemical Industry     

可食性包装在冷却肉保鲜中的应用

系统阐述可食性包装的特点以及在冷却肉保鲜中的应用。介绍可食性包装减少冷却肉中水分和汁液损失,抑制油脂氧化和微生物生长繁殖,以及提高冷却肉品质和延长其货架期的研究进展,并提出目前可食性包装应用中存在的问题。     

可食性蛋白膜研究进展

传统塑料包装材料引起环境污染问题越来越受到人们关注,其安全性也受到人们质疑,发展新型包装材料,将会是未来方向;蛋白膜以其可生物降解性、可食性、隔油、阻气等性能,正成为国内外研究热点。该文阐述蛋白膜成膜机理、膜的特性及分类,并介绍大豆分离蛋白膜、小麦面筋蛋白膜等可食性蛋白膜国内外研究现状。     

响应面分析法优化冷鲜牛肉可食性涂层的研究

采用响应面分析法优化冷鲜牛肉可食性涂层的组成,有效延长其货架期。研究以冷鲜牛肉的硫代巴比妥酸值为考察对象,采用响应面分析法研究由大豆分离蛋白、豌豆淀粉和三乙酸甘油酯制备的可食性涂层对冷鲜牛肉品质的影响,进一步对响应面分析优化结果进行实验验证,两者误差为7.3%,证明响应面分析法的结果真实可靠。因此,冷鲜牛肉可食性涂层的最佳组成为大豆分离蛋白(3.00%)、豌豆淀粉(3.24%)和三乙酸甘油酯(1.21%)。     

可食性玉米醇溶蛋白膜研究进展

该文介绍目前国内外可食性玉米醇溶蛋白膜研究现状及对发展趋势进行分析,指出制备以玉米醇溶蛋白为基质可食性复合包装膜是一个新的发展方向。     

Recent advances in modified atmosphere packaging and edible coatings to maintain quality of fresh-cut fruits and vegetables

Processing of fruits and vegetables generates physiological stresses in the still living cut tissue, leading to quality deterioration and shorter shelf life as compared with fresh intact produces. Several strategies can be implemented with the aim to reduce the rate of deterioration of fresh-cut commodities. Such strategies include low temperature maintenance from harvest to retail and the application of physical and chemical treatments such as modified atmosphere packaging (MAP) with low O₂ and high CO₂ levels and antioxidant dips. Other technologies such as edible coatings with natural additives, new generation of coatings using nanotechnological solutions such as nanoparticles, nanoencapsulation, and multilayered systems, and nonconventional atmospheres such as the use of pressurized inert/noble gases and high levels of O₂ have gained a lot of interest as a possibility to extend the shelf life of minimally processed fruits and vegetables. However, the high perishability of these products challenges in many cases their marketability by not achieving sufficient shelf life to survive the distribution system, requiring the combination of treatments to assure safety and quality. This review reports the recent advances in the use of MAP, edible coatings, and the combined effect of both technologies to extend the shelf life of fresh-cut fruits and vegetables.     

Edible packaging from hydroxypropyl thermoplastic cassava starch,agar and maltodextrin blends produced by cast extrusion

Edible packaging from hydroxypropyl cassava starch with different degrees of substitution (DS), agar and maltodextrin films was produced by conventional cast extrusion. Microstructures showed hydrophobic agar aggregates (100–200 µm) dispersed in film matrices, giving nonsmooth surfaces that enhanced wettability (17%–31%). Higher DS increased interaction between agar and maltodextrin via hydrogen bonding due to greater plasticisation and enhanced formation of agar networks. Lower DS starch showed instability with lower tensile strength (23% of higher DS), giving poor processability that was greatly improved by agar (20%). Water vapour and oxygen permeability depended on microstructures and hydrophilic–hydrophobic properties of the matrices which were decreased by 25% and 58% with combined agar and maltodextrin, respectively. Crystallinity of the films depended on plasticisation, with enhanced mobility that reduced transparency. Agar and maltodextrin inhibited recrystallisation of starch. Findings suggested that higher DS starch and agar enhanced extrusion processability, while maltodextrin increased plasticisation and reduced network strength.     

植酸改性淀粉可食性膜材料的研究

研究了植酸改性淀粉的成膜条件及其可食性膜的性能。植酸改性淀粉可食性膜的最佳成膜条件是:甘油10%,山梨醇5%,羧甲基纤维素钠3%,40-50℃干燥;湿法植酸改性淀粉膜的耐水性和阻湿性优于浸渍法植酸改性淀粉膜和原淀粉膜,浸渍法植酸改性淀粉膜强度有所提高。     

可食性膜制备及改性研究

可食性膜是当前包装材料研究中较为热门课题,并已应用到商品流通许多领域,特别是在食品包装和保鲜领域;该文主要对各类可食性膜制备及膜改性工艺进行综述。     

玉米淀粉与小麦淀粉复合可食用膜工艺研究

以玉米淀粉和小麦淀粉为成膜基质,采用流延法制备可食用膜,以膜的力学性能作为考查指标,通过单因素实验研究质量比、山梨醇含量、柠檬酸含量、增强剂含量、糊化温度、糊化时间对力学性能的影响,在单因素基础上,以四因素三水平的正交实验优化的最佳制膜工艺条件。结果表明,在淀粉溶液浓度60 g/L,玉米淀粉和小麦淀粉质量比40∶60,山梨醇含量0.6%,柠檬酸含量2.5%,增强剂含量1.4%,糊化温度85℃,糊化时间40 min,干燥4~6 h的最佳制膜工艺条件下,复合膜的拉伸强度为14~15 MPa,断裂伸长率为30%~33%。      

涂膜处理和酸处理对提高双孢蘑菇储藏稳定性的研究

为了提高双孢蘑菇(Agaricus bisporus)的储藏稳定性,本研究分别采用了三种不同的方法对双孢蘑菇进行处理,它们分别是:酸处理、涂膜处理和酸与涂膜相结合的处理,然后分别测定了储藏过程中的失重率、硬度、色泽变化、多酚氧化酶(PPO)活力和过氧化物酶活力(POD),探讨了不同处理方法对双孢蘑菇储藏稳定性的影响。结果表明:酸与涂膜相结合的处理方式具有最优的效果,它能弥补酸处理和涂膜处理各自的不足之处,既能降低失重率,保持硬度,又能抑制酶活,更好地保持双孢蘑菇的色泽。      

Biopolymer-based antimicrobial packaging: a review

The term antimicrobialpackaging encompasses any packaging technique(s) used to control microbial growth in a food product. These include packaging materials and edible films and coatings that contain antimicrobial agents and also techniques that modify the atmosphere within the package. In recent years, antimicrobial packaging has attracted much attention from the food industry because of the increase in consumer demand for minimally processed, preservative-free products. Reflecting this demand, the preservative agents must be applied to packaging in such away that only low levels of preservatives come into contact with the food. The film or coating technique is considered to be more effective, although more complicated to apply. New antimicrobial packaging materials are continually being developed. Many of them exploit natural agents to control common food-borne microorganisms. Current trends suggest that, in due course, packaging will generally incorporate antimicrobial agents, and the sealing systems will continue to improve. The focus of packaging in the past has been on the appearance, size, and integrity of the package. A greater emphasis on safety features associated with the addition of antimicrobial agents is perhaps the next area for development in packaging technology.     

纳米淀粉的制备及其在可食性薄膜中的应用研究进展

天然高分子基纳米复合薄膜不仅耗能低,缓解了合成材料的不可降解对生存环境的污染及原料日益枯竭的压力,而且实现了资源的可持续发展,由于纳米颗粒的增强作用,复合薄膜呈现出比常规可食性膜更独特、更优异的性质,具有价廉易得、可再生、污染小等特点。文章对国内外纳米淀粉的制备方法进行了综述,介绍了物理、化学等方法制备纳米淀粉的方法,简要阐述了其在纳米复合可食性膜中的应用,并对其改善天然高分子薄膜的性能的研究进展进行了归纳,以期为进一步研究新型纳米复合可食用膜提供依据。     

微波处理对可食性壳聚糖/淀粉复合膜性能的影响

以壳聚糖和淀粉为主要原料制备了可食性复合膜,考察了不同微波处理功率、处理时间对可食性复合膜性能的影响。在固定的处理时间范围内,升高微波功率,复合膜的抗张强度显著增加,断裂伸长率降低。对于固定的微波功率,膜的抗张强度随处理时间的延长而提高,但微波处理时间在30s以上时,膜表面产生气泡;处理时间在25s时,膜的外观和抗拉强度理想。     

Moisture sorption and thermodynamic properties of cassava starch and soy protein concentrate based edible films

Moisture sorption isotherms and thermodynamic properties of cassava starch and soy protein concentrate–based edible films were investigated. Equilibrium moisture content was determined at various temperatures (10, 20, 30 and 40 °C) and relative humidities (17–83%) using gravimetric method, and the results were analysed using four sorption isotherm models. The equilibrium moisture of edible films (both adsorption and desorption modes) decreased with soy protein concentrate addition and temperature at constant water activity. The monolayer moisture content values of cassava starch–soy protein concentrate edible films decreased with increase in temperature and soy protein level. GAB and Oswin models (%RMS ≤10) best described the isotherms of the biofilms with the monolayer moisture contents, isosteric enthalpy and entropy higher for adsorption with significant kinetic compensations. The moisture sorption and thermodynamic properties of cassava starch–soy protein concentrate edible films showed that they are suitable for packaging applications.     

Influence of hydrocolloid nature on the structure and functional properties of emulsified edible films

To investigate the influence of polymer behaviors on the structure and the functional properties of emulsified films, agar (AG) and cassava starch (CAS) were used as hydrocolloid continuous phases in which hydrogenated vegetable oil (VGB81) was dispersed. Different ratios of hydrophilic/hydrophobic materials (HB/HL) were also used in film formulations to study the evolution of film-emulsion structure. Microscopically observed, VGB–CAS emulsified films exhibit a similar bilayer structure. However, there was just a migration and an aggregation of lipid particles. There was no coalescence which could form a continuous “lipid layer” necessary for an effective barrier. Moreover, they could not be made with a HB/HL ratio greater than 0.7:1. Conversely, AG chains set into gel, which solidifies film-forming emulsion before drying, leading to a fixed macronetwork structure. Films made with a high HB/HL ratios lead to a film structure becoming like a multilayer system. The water vapor permeability of emulsified films is better found when HB/HL ≥ 1:1 when films are formed only with gelling polysaccharide (AG). In addition, there is no relationship between the moisture sorption and the moisture permeability of emulsified films. In contact with liquid water, brief sorption and swelling surface are observed for VGB–AG film surface and rapid absorption following a temporary hydrophobicity is found in the case of VGB–CAS films. While the mechanical properties of VGB–CAS films are strongly altered, those of VGB–AG films are considered to be sufficient for most of applications.