A review on colorimetric indicators for monitoring product freshness in intelligent food packaging: Indicator dyes,preparation methods,and applications

Intelligent food packaging system exhibits enhanced communication function by providing dynamic product information to various stakeholders (e.g., consumers, retailers, distributors) in the supply chain. One example of intelligent packaging involves the use of colorimetric indicators, which when subjected to external stimuli (e.g., moisture, gas/vapor, electromagnetic radiation, temperature), display discernable color changes that can be correlated with real-time changes in product quality. This type of interactive packaging system allows continuous monitoring of product freshness during transportation, distribution, storage, and marketing phases. This review summarizes the colorimetric indicator technologies for intelligent packaging systems, emphasizing on the types of indicator dyes, preparation methods, applications in different food products, and future considerations. Both food and nonfood indicator materials integrated into various carriers (e.g., paper-based substrates, polymer films, electrospun fibers, and nanoparticles) with material properties optimized for specific applications are discussed, targeting perishable products, such as fresh meat and fishery products. Colorimetric indicators can supplement the traditional “Best Before” date label by providing real-time product quality information to the consumers and retailers, thereby not only ensuring product safety, but also promising in reducing food waste. Successful scale-up of these intelligent packaging technologies to the industrial level must consider issues related to regulatory approval, consumer acceptance, cost-effectiveness, and product compatibility.     

新型食品包装材料的发展概况及趋势

食品包装是食品的外部保护, 可以防止食品免受外界因素的影响而发生感官或营养成分的变化。传统的食品包装材料不仅会给环境带来巨大压力, 而且从食品包装迁移至食品中的化学物质也会给食品安全和质量带来负面影响。随着人们对食品包装材料的安全性越来越关注, 很多新型的食品包装材料成为研究热点。本文对几种具有较大应用前景的可降解材料、可食材料进行了综述, 包括天然高分子材料、微生物合成高分子材料、聚乳酸(poly lactic acid, PLA)等新型食品包装材料的研究现状和亟待解决的问题, 简要介绍了活性包装和智能包装的发展, 并对未来食品包装的发展趋势提出方向。     

食品智能包装新鲜度指示剂研究进展

作为智能包装不可缺少的一部分——新鲜度指示剂,通过指示敏感材料,与食品腐败过程中产生的特定产物发生反应,并将反应结果转换成易于消费者直接观察和判断的信号,如：颜色信号、电信号、荧光信号等,为消费者提供实时质量监控信息,本文综述了食品智能包装新鲜度指示剂的分类,包括CO₂敏感型指示剂、TVB-N敏感型指示剂、pH敏感型指示剂及其成型工艺,涵盖了食品智能包装新鲜度指示剂的应用,旨在为食品智能包装新鲜度指示剂的发展提供参考,为食品损失和污染等传统包装问题提供了潜在的解决方案,其后续发展应朝着方便、快捷、实时显示食品质量变化的方向,以减少因食品质量差和安全问题带来的健康问题,研发新型的新鲜度指示剂,有利于将智能包装技术推广至更多的包装应用中,为产品质量提供理论指导与技术支撑。     

数字化食品在新时代下的发展与挑战

数字化社会的大背景下,食品行业也正在发生着巨大变化。数字化的发展为食品产业的转移/更新/革命带来了新机遇,既是食品行业健康发展的必要需求,也是顺应国家时代发展的需求。作为数字化转型的产物,数字化食品是利用物联网、云计算、人工智能、区块链技术等数字化技术对食品原料物性、营养特性、人群营养特征等信息数据化和整合分析,与食品生物合成、食品重组、增材制造、智能化加工、智慧化物流、智慧化包装等高新技术深度融合后产生的食品,具备精准或定制化制造和供给的典型特征。目前,食品科学正在逐步通过数字技术与实体食品企业的深度融合来形成数字化食品的产业模式。基于此,本文对数字化食品的研究进展与关键技术进行了阐述,并对该领域的未来应用和挑战进行了展望。     

Nanoemulsions: Synthesis,Characterization, and Application in Bio‐Based Active Food Packaging

The increasing demands for foods with fresh‐like characteristics, lower synthetic additive and preservative contents, and low environmental footprint, but still safe to consume, have guided researchers and industries toward the development of milder processing technologies and more eco‐friendly packaging solutions. As sustainability acquires an increasingly critical relevance in food packaging, bio‐based and/or biodegradable materials stand out as suitable alternatives to their synthetic counterparts. In this context, the use of nanoemulsions has represented a step forward for improving the performance of sustainable food packaging devices, especially for the successful incorporation of new compounds and functionalities into conventional films and coatings. This class of emulsions, featuring unique optical stability and rheological properties, has been developed to protect, encapsulate, and deliver hydrophobic bioactive and functional compounds, including natural preservatives (such as essential oils from plants), nutraceuticals, vitamins, colors, and flavors. This article presents the surfactants (including naturally occurring proteins and carbohydrates), dispersants, and oil‐soluble functional compounds used for designing food‐grade nanoemulsions intended for packaging applications. The improved kinetic stability, bioavailability, and optical transparency of nanoemulsions over conventional emulsions are discussed considering theoretical concepts and real experiments. Bottom‐up and top‐down approaches of nanoemulsion fabrication are described, including high‐energy (such as high‐pressure homogenizers, microfluidics, ultrasound, and high‐speed devices) and low‐energy methods (for instance, phase inversion and spontaneous emulsification). Finally, incorporation of nanoemulsions in biopolymer matrixes intended for food packaging applications is also addressed, considering current characterization techniques as well as their potential antimicrobial activity against foodborne pathogens.     

Active and intelligent packaging: The indication of quality and safety

The food industry has been under growing pressure to feed an exponentially increasing world population and challenged to meet rigorous food safety law and regulation. The plethora of media consumption has provoked consumer demand for safe, sustainable, organic, and wholesome products with “clean” labels. The application of active and intelligent packaging has been commercially adopted by food and pharmaceutical industries as a solution for the future for extending shelf life and simplifying production processes; facilitating complex distribution logistics; reducing, if not eliminating the need for preservatives in food formulations; enabling restricted food packaging applications; providing convenience, improving quality, variety and marketing features; as well as providing essential information to ensure consumer safety. This chapter reviews innovations of active and intelligent packaging which advance packaging technology through both scavenging and releasing systems for shelf life extension, and through diagnostic and identification systems for communicating quality, tracking and brand protection.     

Current status of biobased and biodegradable food packaging materials: Impact on food quality and effect of innovative processing technologies

Fossil-based plastic materials are an integral part of modern life. In food packaging, plastics have a highly important function in preserving food quality and safety, ensuring adequate shelf life, and thereby contributing to limiting food waste. Meanwhile, the global stream of plastics into the oceans is increasing exponentially, triggering worldwide concerns for the environment. There is an urgent need to reduce the environmental impacts of packaging waste, a matter raising increasing consumer awareness. Shifting part of the focus toward packaging materials from renewable resources is one promising strategy. This review provides an overview of the status and future of biobased and biodegradable films used for food packaging applications, highlighting the effects on food shelf life and quality. Potentials, limitations, and promising modifications of selected synthetic biopolymers; polylactic acid, polybutylene succinate, and polyhydroxyalkanoate; and natural biopolymers such as cellulose, starch, chitosan, alginate, gelatine, whey, and soy protein are discussed. Further, this review provides insight into the connection between biobased packaging materials and innovative technologies such as high pressure, cold plasma, microwave, ultrasound, and ultraviolet light. The potential for utilizing such technologies to improve biomaterial barrier and mechanical properties as well as to aid in improving overall shelf life for the packaging system by in-pack processing is elaborated on.     

Cold atmospheric pressure plasma and low energy electron beam as alternative nonthermal decontamination technologies for dry food surfaces: A review

BackgroundDry food products are often highly contaminated, and dry stress-resistant microorganisms, such as certain types of Salmonella and bacterial spores, can be still viable and multiply if the product is incorporated into high moisture food products or rehydrated. Traditional technologies for the decontamination of these products have certain limitations and drawbacks, such as alterations of product quality, environmental impacts, carcinogenic potential and/or lower consumer acceptance. Cold atmospheric pressure plasma (CAPP) and low energy electron beam (LEEB) are two promising innovative technologies for microbial inactivation on dry food surfaces, which have shown potential to solve these certain limitations.Scope and approachThis review critically summarizes recent studies on the decontamination of dry food surfaces by CAPP and LEEB. Furthermore, proposed inactivation mechanisms, product-process interactions, current limitations and upscaling potential, as well as future trends and research needs for both emerging technologies, are discussed.Key findings and conclusionsCAPP and LEEB are nonthermal technologies with a high potential for the gentle decontamination of dry food surfaces. Both technologies have similarities in their inactivation mechanisms. Due to the limited penetration depth of both technologies, product-process interactions can be minimized by maintaining product quality. A first demonstrator with Technology Readiness Level (TRL) 7 for LEEB has already been introduced into the food industry for the decontamination of herbs and spices. Compared with LEEB, CAPP is at the advanced development stage with TRL 5, for which further work is essential to design systems that are scalable to industrial requirements.     

Active Packaging Applications for Food

The traditional role of food packaging is continuing to evolve in response to changing market needs. Current drivers such as consumer's demand for safer, “healthier,” and higher‐quality foods, ideally with a long shelf‐life; the demand for convenient and transparent packaging, and the preference for more sustainable packaging materials, have led to the development of new packaging technologies, such as active packaging (AP). As defined in the European regulation (EC) No 450/2009, AP systems are designed to “deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food.” Active packaging materials are thereby “intended to extend the shelf‐life or to maintain or improve the condition of packaged food.” Although extensive research on AP technologies is being undertaken, many of these technologies have not yet been implemented successfully in commercial food packaging systems. Broad communication of their benefits in food product applications will facilitate the successful development and market introduction. In this review, an overview of AP technologies, such as antimicrobial, antioxidant or carbon dioxide‐releasing systems, and systems absorbing oxygen, moisture or ethylene, is provided, and, in particular, scientific publications illustrating the benefits of such technologies for specific food products are reviewed. Furthermore, the challenges in applying such AP technologies to food systems and the anticipated direction of future developments are discussed. This review will provide food and packaging scientists with a thorough understanding of the benefits of AP technologies when applied to specific foods and hence can assist in accelerating commercial adoption.     

Trends and challenges of biopolymer-based nanocomposites in food packaging

The ultimate goal of new food packaging technologies, in addition to maintaining the quality and safety of food for the consumer, is to consider environmental concerns and reduce its impacts. In this regard, one of the solutions is to use eco-friendly biopolymers instead of conventional petroleum-based polymers. However, the challenges of using biopolymers in the food packaging industry should be carefully evaluated, and techniques to eliminate or minimize their disadvantages should be investigated. Many studies have been conducted to improve the properties of biopolymer-based packaging materials to produce a favorable product for the food industry. This article reviews the structure of biopolymer-based materials and discusses the trends and challenges of using these materials in food packaging technologies with the focus on nanotechnology and based on recent studies.     

Antimicrobial activity of biodegradable polysaccharide and protein-based films containing active agents

Significant interest has emerged in the introduction of food packaging materials manufactured from biodegradable polymers that have the potential to reduce the environmental impacts associated with conventional packaging materials. Current technologies in active packaging enable effective antimicrobial (AM) packaging films to be prepared from biodegradable materials that have been modified and/or blended with different compatible materials and/or plasticisers. A wide range of AM films prepared from modified biodegradable materials have the potential to be used for packaging of various food products. This review examines biodegradable polymers derived from polysaccharides and protein-based materials for their potential use in packaging systems designed for the protection of food products from microbial contamination. A comprehensive table that systematically analyses and categorizes much of the current literature in this area is included in the review.     

用于食品质量监测的pH智能指示剂的研究进展

近年来,消费者对于食品安全要求的改变促进了包装新技术的发展。目前用于食品质量监测的智能包装技术主要有指示剂、数据载体装置以及传感器等。其中,pH智能指示剂由于其成本低、体积小、制备方便和指示效果好等优点而成为研究热点。通常来说,指示剂是由负载基和pH染料组成。同时天然pH染料如茜素、姜黄素、类胡罗卜素、花青素等对于环境酸碱性的改变能表现出明显的颜色变化。以天然pH染料制备的pH智能指示剂能够传递食品的实时信号（颜色、化学或电子）,以表现实时的质量信息。本文主要对以天然染料和生物聚合物为基础的pH智能指示剂的研究现状进行了概述,讨论了基于天然pH染料和合成pH染料相比的pH智能指示剂的重要性,以及未来的研究趋势。     

脉冲强光杀菌技术在食品及包装材料中应用研究进展

脉冲强光是一种高效、环保的新型非热杀菌技术,在食品领域具有巨大的发展潜力。本文综述了脉冲强光技术的杀菌机理及其在果蔬、肉制品、乳制品、食品包装材料等领域中的应用,脉冲强光与其他保鲜技术的耦合效果,脉冲强光技术在食品工业中的应用实例以及脉冲强光使用的安全性。脉冲强光不仅能广泛杀灭多种致病菌而且基本不改变各类食品及食品包材的各项性质,在提高食品安全性和延长食品保质期方面有巨大的应用潜力,脉冲强光与其他保鲜技术的耦合与单一保鲜技术相比在杀菌效果、感官品质、营养素含量的保留等方面也都具有更好的效果。本文为研究者进一步了解脉冲强光杀菌技术、拓展其应用领域提供理论参考。     

食品包装与环境发展

食品包装工业发展迅速,常用食品包装材料有高分子、金属、纸和玻璃等。这些食品包装材料在生产过程中对环境均有一定的污染,在使用后不正确的处理方法以及食品包装中残留的微生物又导致对环境的进一步污染,同时食品过度包装还造成对环境资源的巨大破坏。为使食品包装工业与环境能协调发展,人们应注重食品包装的清洁生产、发展绿色食品包装、简化食品包装以及提高环保意识。     

Past, current and potential utilisation of active and intelligent packaging systems for meat and muscle-based products: A review

Interest in the use of active and intelligent packaging systems for meat and meat products has increased in recent years. Active packaging refers to the incorporation of additives into packaging systems with the aim of maintaining or extending meat product quality and shelf-life. Active packaging systems discussed include oxygen scavengers, carbon dioxide scavengers and emitters, moisture control agents and anti-microbial packaging technologies. Intelligent packaging systems are those that monitor the condition of packaged foods to give information regarding the quality of the packaged food during transport and storage. The potential of sensor technologies, indicators (including integrity, freshness and time-temperature (TTI) indicators) and radio frequency identification (RFID) are evaluated for potential use in meat and meat products. Recognition of the benefits of active and intelligent packaging technologies by the food industry, development of economically viable packaging systems and increased consumer acceptance is necessary for commercial realisation of these packaging technologies.     

食品包装对环境的影响

食品工业的发展极大地推动了食品包装工业的发展，常用食品包装材料有高分子、金属、纸和玻璃等。这些食品包装材料在生产过程中对环境均有一定的污染，在使用后不正确的处理方法以及食品包装中残留的微生物又导致对环境的进一步污染，同时食品过度包装还造成对环境资源的巨大破坏。为使食品包装工业与环境能协调发展，人们应在食品包装的清洁生产、发展绿色食品包装、简化食品包装以及提高环保意识等方面做出努力。     

Applications of natural polysaccharide-based pH-sensitive films in food packaging: Current research and future trends

With the increased awareness of food safety and growing environmental concern of plastic packaging disposal, the research and development of novel food packaging is extremely urgent and attracts much attention. Natural polysaccharides are ideal candidate materials to develop “green” food packaging due to their biodegradable properties and good film-forming properties. Especially, the natural polysaccharides-based intelligent films can provide consumers the real-time information about the quality and safety of the packaged food through the pH-sensitive indicators. Consequently, this paper summarized the current researches on the development of natural polysaccharides-based pH-sensitive films. Then, the applications of natural polysaccharides-based pH-sensitive films in food packaging, including the packaging for meat products, fruits and vegetables, etc., are emphasized. Finally, an overview of the trends/challenges of pH-sensitive films in food packaging is discussed. Taken together, the natural polysaccharide-based pH-sensitive food packaging films show more advantages as compared with the common food package films, which can not only protect the packaged food, but also monitor the quality of packaged food in real time. Nevertheless, the further studies should continue to focus on the commercially sustainable key points including consumer acceptance and trust, cost, regulatory considerations and multifunctional performance of the pH-sensitive food packaging films.     

Recovery of High Value‐Added Nutrients from Fruit and Vegetable Industrial Wastewater

The industrial processing water of fruit and vegetables has raised serious environmental concerns due to the presence of many important bioactive compounds being disposed in the wastewater. Bioactive compounds have great potential for the food industry to optimize their process and to recover these compounds in order to develop value‐added products and to reduce environmental impacts. However, to achieve this goal, some challenges need to be addressed such as safety assurance, technology request, product regulations, cost effectiveness, and customer factors. Therefore, this review aims to summarize the recent advances of bioactive compounds recovery and the current challenges in wastewater from fruit and vegetable processing industry, including fruit and beverage, soybean by‐products, starch and edible oil industry. Moreover, future direction for novel and green technology of bioactive compounds recovery are discussed, and a prospect of bioactive compounds reuse and sustainable development is proposed.     

Active and intelligent packaging for food: Is it the future?

This paper gives an overview of the legal consequences of a new EU framework regulation on food contact materials which includes controls on active and intelligent packaging. Recent developments in active and intelligent packaging systems are described, two examples of which aim at achieving improvements in quality and safety of food products. The first one is an on-command preservative-releasing packaging system. The second system is an intelligent concept, based on the development of a non-invasive microbial growth sensor to monitor the sterility of food products.