Art and Science behind Modified Starch Edible Films and Coatings: A Review

Technological advances have led to increased constraints regarding food packaging, mainly due to environmental issues, consumer health concerns, and economic restrictions associated therewith. Hence, food scientists and technologists are now more focused on developing biopolymer packages. Starch satisfies all the principal aspects making it a promising raw material for edible coatings/films. Modified starch has grabbed much attention, both at the academic as well as at the industrial level, because these films exhibit dramatic improvement in filming properties without involving any significant increase in cost of production. Various methods, additives used, and recent advances in the field of starch film production are discussed in detail in this review, which also provides an overview of the available information along with recent advances in modified starch film packaging.     

Edible and Biodegradable Starch Films: A Review

Mainly due to environmental aims, petroleum-based plastics are being replaced by natural polymers. In the last decades, starch has been evaluated in its film-forming ability for applications in the food packaging area. Characteristics of the starch film matrices, the film formation methods, and physicochemical properties of the starch films are reviewed in this paper. The influences of different components added in casting methods and thermoplastic processes have been also analyzed. Comparison of mechanical properties of newly prepared starch films and stored films reveals that the recrystallization phenomenon made the films more rigid and less stretchable. These effects can be inhibited by adding other polymers to the starch matrix. Other approaches to improve the starch films’ properties are the reinforcement by adding organic or inorganic fillers to the starch matrix as well as the addition of functional compounds. In this way starch films have improved mechanical and barrier properties and can act as a bioactive packaging. Physicochemical properties of the starch films showed a great variability depending on the compounds added to the matrix and the processing method. Nevertheless, dry methods are more recommendable for film manufacturing because of the greater feasibility of the industrial process. In this sense, a better understanding of the nano and microstructural changes occurring in the matrices and their impact on the film properties is required.     

Edible Films and Coatings from Soy Protein

A method was developed by which films could be prepared from commercial isolated soy protein (ISP). ISP was treated with alkali (ATISP) to alter film orooerties. Water vapor oermeability (WVP). oxygen‘permeability (O₂P), tensile strength (TS), percent elongatidn (%E), and appearance of ISP and ATISP were compared. Alkali treatment had no effect on WVP. O₂P, and TS, gave hieher %E, and improved film appearance. Films properties were also compared at pH 6, 8, 10, and 12. In general, pH 6 gave higher WVP and O₂P and lower TS and %E; while higher pH gave lower WVP and O₂P and higher TS and %E. ATISP films could not be produced at pH 6. Film appearance generally improved with increased pH.     

Advances in Edible Coatings for Fresh Fruits and Vegetables: A Review

Edible coatings are an environmentally friendly technology that is applied on many products to control moisture transfer, gas exchange or oxidation processes. Edible coatings can provide an additional protective coating to produce and can also give the same effect as modified atmosphere storage in modifying internal gas composition. One major advantage of using edible films and coatings is that several active ingredients can be incorporated into the polymer matrix and consumed with the food, thus enhancing safety or even nutritional and sensory attributes. But, in some cases, edible coatings were not successful. The success of edible coatings for fresh products totally depends on the control of internal gas composition. Quality criteria for fruits and vegetables coated with edible films must be determined carefully and the quality parameters must be monitored throughout the storage period. Color change, firmness loss, ethanol fermentation, decay ratio and weight loss of edible film coated fruits need to be monitored. This review discusses the use of different edible coatings (polysaccharides, proteins, lipids and composite) as carriers of functional ingredients on fresh fruits and vegetables to maximize their quality and shelf life. This also includes the recent advances in the incorporation of antimicrobials, texture enhancers and nutraceuticals to improve quality and functionality of fresh-cut fruits. Sensory implications, regulatory status and future trends are also reviewed.     

Development of Edible Films and Coatings with Antimicrobial Activity

Over the last years, considerable research has been conducted to develop and apply edible films and coatings made from a variety of agricultural commodities and/or wastes of food product industrialization. Such biopolymers include polysaccharides, proteins, and their blends. These materials present the possibility of being carriers of different additives, such as antimicrobial, antioxidant, nutraceuticals, and flavorings agents. In particular, the use of edibles films and coatings containing antimicrobials has demonstrated to be a useful tool as a stress factor to protect foodstuff against spoilage flora and to decrease the risk of pathogen growth. The more commonly antimicrobials used are organic acids, chitosan, nisin, the lactoperoxidase system, and some plant extracts and their essential oils. For the selection of an antimicrobial, it must be considered the effectiveness against the target microorganism and also the possible interactions among the antimicrobial, the film-forming biopolymer, and other food components present. These interactions can modify the antimicrobial activity and the characteristics of the film being these key factors for the development of antimicrobial films and coatings. The main objective of this article is to review the bibliography of the last years concerning the main hydrocolloids and antimicrobials used for developing edible films and coatings, the methods used to evaluate the antimicrobial activity, the applications and the legislation concerning edible films and coatings. Also, the different strategies related to the modification of structural characteristics and the future trends in the development are discussed. The information update will help to improve the design, development, and application of edible films and coatings tending to increase the safety and quality of food products and to prepare for food legislation changes that might be necessary while identifying future trends concerning a better functionality of edible films thought as a stress factor for lengthening shelf life of food products.     

可食性膜的研究进展

本文从可食性膜的分类及其特点、应用以及发展趋势等几个方面对可食性膜近几年来国内外研究进展进行了综述。     

Edible Films and Coatings as Carriers of Living Microorganisms: A New Strategy Towards Biopreservation and Healthier Foods

Edible films and coatings have been extensively studied in recent years due to their unique properties and advantages over more traditional conservation techniques. Edible films and coatings improve shelf life and food quality, by providing a protective barrier against physical and mechanical damage, and by creating a controlled atmosphere and acting as a semipermeable barrier for gases, vapor, and water. Edible films and coatings are produced using naturally derived materials, such as polysaccharides, proteins, and lipids, or a mixture of these materials. These films and coatings also offer the possibility of incorporating different functional ingredients such as nutraceuticals, antioxidants, antimicrobials, flavoring, and coloring agents. Films and coatings are also able to incorporate living microorganisms. In the last decade, several works reported the incorporation of bacteria to confer probiotic or antimicrobial properties to these films and coatings. The incorporation of probiotic bacteria in films and coatings allows them to reach the consumers’ gut in adequate amounts to confer health benefits to the host, thus creating an added value to the food product. Also, other microorganisms, either bacteria or yeast, can be incorporated into edible films in a biocontrol approach to extend the shelf life of food products. The incorporation of yeasts in films and coatings has been suggested primarily for the control of the postharvest disease. This work provides a comprehensive review of the use of edible films and coatings for the incorporation of living microorganisms, aiming at the biopreservation and probiotic ability of food products.     

Lipid Addition to Improve Barrier Properties of Edible Starch-based Films and Coatings

ABSTRACT: Effects of formulation (lipid presence, type of starch, and plasticizer) on microstructure, water vapor (WVP) and gas (GP) permeabilities of films and coatings were analyzed. Plasticizer was necessary to maintain film and coating integrity and to avoid pores and cracks. Films made from high amylose starch showed lower WVP and GP than regular corn starch films; permeabilities of films with sorbitol (20 g/L) were lower than those with glycerol. The addition of 2g/L sunflower oil to the formulations decreased WVP of starch-based films; X-ray diffraction and Differential Scanning Calorimetry experiments demonstrated that films with plasticizer and lipid showed lower crystalline-amorphous ratio compared to films without additives. Microstructural observations helped explain the decrease of the film permeabilities during storage.     

蛋白质基可食性生物聚合膜的研究进展

可食性生物聚合膜的开发和应用是食品、药品和包装行业十分重视的课题。其中,蛋白膜以其营养丰富和隔油阻气等性能,成为国内外研究的热点。主要介绍以蛋白质为基质的可食性生物聚合膜的研究进展,并对其发展趋势提出观点。     

Recent Advances on Edible Films Based on Fruits and Vegetables—A Review

Food packaging materials are traditionally expected to contain foodstuffs and protect them from deteriorating agents. Although petroleum‐derived polymers have been widely used for this purpose, the rising concern with their nonrenewable and/or nonbiodegradable nature paves the route for the development of greener alternatives, including polysaccharides and polypeptides. The use of these food‐grade biomacromolecules, in addition to fruits and vegetables, provides edible packaging with suitable physical‐mechanical properties as well as unique sensory and nutritional characteristics. This text reviews the chronological development pathway of films based on fruit and vegetable purees, pomaces, and extracts. Recent advances are extensively reviewed with an emphasis on the role that each film component plays in the resulting materials, whose production methods are examined from a technical standpoint and essential properties are compiled and contrasted to their conventional, synthetic counterparts. Finally, this comprehensive review discusses advantages and limitations of edible films based on fruits and vegetables.     

Moisture Loss and Lipid Oxidation for Precooked Beef Patties Stored in Edible Coatings and Films

Edible/biodegradable wheat gluten (WG), soy protein (SP), carrageenan (CA) and chitosan (CH) films and coatings were used on precooked beef patties. After 3 d of refrigerated storage, no difference was found in moisture loss between WG, SP, and CH film-wrapped patties and unpackaged patties (control-A). All coatings were as effective as polyvinyl chloride film (control-B) in reducing moisture loss. CA film decreased moisture loss but not as effective as control-B. WG, SP, and CA coatings and CA film reduced thiobarbituric acid-reactive substances and hexanal values compared to control-A. WG-coated patties had lower hexanal values than control-B samples. WG, SP, and CH films were not effective in controlling lipid oxidation.     

Gelatin-Chitosan Composite Films and Edible Coatings to Enhance the Quality of Food Products: Layer-by-Layer vs. Blended Formulations

Two different approaches, blending and layer-by-layer electrostatic deposition (LbL), were utilized to combine two biopolymers, gelatin and chitosan, in edible films or coatings. The performance of the blended and LbL composite films and single-component gelatin and chitosan films was compared in terms of mechanical, optical, and spectroscopic properties. In parallel, edible coatings based on these formulations were applied on a food model: fresh-cut melon. Physiological, textural, and microbiological parameters of the coated fruit were studied in comparison with non coated control. Surprisingly, in spite of the higher thickness, the composite films and especially the LbL formulation demonstrated enhanced water vapor permeability as compared to single-component films. The LbL film had higher strength and better elasticity than the blended one. All edible coatings containing chitosan effectively inhibited microbial growth on fresh-cut melons. The LbL formulation demonstrated the most effective inhibition of the total microbial growth especially after 5–7 days of storage, while the blended formulation demonstrated high antifungal activity after 11 days of storage. The LbL formulation demonstrated superior performance in preservation of fruit texture and also slightly reduced fruit weight loss, while the blended formulation did not improve these parameters. Both composite coatings do not obstruct fruit gas exchange and do not cause accumulation of off-flavor volatiles.     

Fruit Wastes Fermentation for Phenolic Antioxidants Production and Their Application in Manufacture of Edible Coatings and Films

Agro-industrial by-products are important sources of potent bioactive phenolic compounds. These compounds are of extreme relevance for food and pharmacological industries due to their great variety of biological activities. Fermentation represents an environmentally clean technology for production and extraction of these bioactive compounds, providing high quality and high activity extracts, which can be incorporated in foods using coatings/films wax-based in order to avoid alterations in their quality. In this document is presented an overview about importance and benefits of solid-state fermentation, pointing out this bioprocess as an alternative technology for use agro-industrial by-products as substrates to produce valuable secondary metabolites and their applications as food quality conservatives.     

Low-fat Fried Foods with Edible Coatings: Modeling and Simulation

We studied the use of edible films to reduce fat absorption in fried foods. A mathematical model was developed incorporating heat, moisture and fat transfer in the food and the film. Moisture diffusivities of the food and the film were 0.33×10^?7 m²/s and 0.25×10^?7m²/s, respectively. Fat diffusivities were 0.103×10^?8m²/s for the food and 0.604×10^?9m²/s for the film. Thermal diffusivities were 0.102×10^?6m²/s for the food and 0.156×10^?6m²/s for the film. Film diffusivities were determined for gellan gum films at a thickness of 2.0 mm during frying.     

Relationships Between Edible Coatings and Garlic Skin

Porous garlic skin was coated with cross-linked sodium alginate. Penetration of the hydrocolloid and cross-linking agents into the skin were detected by Fourier-Transform Infra-red, X-ray analysis, Inductively Coupled Plasma Atomic Emission Spectrometry and chemical micro-analysis. The skin structure, its wax coating and pores were studied to elucidate the means by which coating agents penetrate the skin. Pathways of skin penetration by gum were hypothesized. Gum penetrates by three pathways: through skin discontinuities, from beneath where the roots are found and directly through the skin. The coating adhered to the outer garlic skin and conformed to its shape.     

大米蛋白的可食用膜

研究了大米蛋白可食用膜的工艺条件，并测定了膜的抗拉强度、延伸率和透水率．实验表明，大米蛋白的质量浓度为5g／dL，甘油的添加量为3g／dL，谷氨酰胺转胺酶的添加量为质量浓度0．2g／dL，反应时间为90min，膜液在80℃处理40min后能得到性能比较好的膜。     

CMC可食性复合膜的研制

以CMC作为基本的成膜物质,研究了琼脂、壳聚糖、硬脂酸对成膜性能的影响,研制出来了具有良好的阻湿性能、阻气性能的新型可食性复合膜。     

草莓的涂膜保鲜研究

本论文主要研究在乳状液体系中各种涂膜保鲜成分如成膜剂、保鲜剂、保湿剂和抗氧化剂等对草莓进行涂膜保鲜效果的影响。研究结果发现,涂膜材料采用乳状液体系能在草莓表面形成连续液膜,而且干燥后表面亮泽,对草莓的感官品质无任何影响。低分子量的壳聚糖既有一定成膜效果,又有良好的抗菌效果。山梨醇能起到良好的控制草莓在常温下的失重问题。抗氧化剂维生素C对控制草莓在存放过程中褐变无显著效果。     

可食用包装膜的研制

以小麦面筋蛋白为原料，制备可食用包装膜。首先，通过单因素试验考察小麦面筋蛋白浓度和增塑剂用量、成膜溶剂、成膜溶液的pH值及热处理等条件对膜性能的影响。并进一步做正交试验，确定了小麦面筋成膜的最佳工艺条件：小麦面筋和甘油配比为3.5:1，乙醇体积分数为40%，成膜溶液的pH值为3，热处理温度为90℃。     

Edible Coatings from Candelilla Wax Microemulsions

Candelilla wax coatings with good gloss were made. The gloss of coatings from ammonia-based microemulsions was improved by addition of gelatin or hydroxypropyl methylcellulose, which also decreased oxygen permeability and decreased water vapor permeability. As coatings on grapefruit, candelilla wax with up to 25% gelatin was usable; much higher gelatin content resulted in anaerobic fermentation. Candelilla coatings with good gloss were also made from morpholine-based wax microemulsions with minimal oleic acid content.