Activities and conformation changes of food enzymes induced by cold plasma: A review

Food endogenous enzymes have impacts on color, texture and flavor of foods during food processing or preservation. Cold plasma is a novel non-thermal food processing technology, which has been extensively studied for contamination elimination and shelf life extension of foods. Particularly, much work has been reported about the effects of cold plasma on enzyme activities and alterations about enzymes conformational structures. It is thus necessary to understand the mechanisms of actions and applications of cold plasma technology in the conformation of food endogenous enzymes. This review focuses on the applications of cold plasma for the inactivation of various endogenous enzymes, including peroxidase, polyphenol oxidase, lysozyme, α-chymotrypsin, alkaline phosphatase, and pectin methylesterase. The activations of several enzymes, such as superoxide dismutase, catalase, and lipase, by cold plasma are also discussed. In addition, this review highlights the transformation of conformational structures including primary and spatial structures induced by chemical reactive species during cold plasma treatments, such as reactive oxygen species and reactive nitrogen species, especially, active sites consisting of prosthetic group and specific amino acids are demonstrated. Both extrinsic and intrinsic factors affecting cold plasma treatments are also described. In general, cold plasma exhibits the ability to activate or inactivate enzymes activities with affecting the conformational structures of enzyme. Further studies should be focused on exploration at molecular level for providing more insight on the interaction mechanism. In addition, equipment and process parameters of cold plasma operation for different fresh food products should be optimized for achieving appropriate control on enzyme variation and obtaining maximum efficiency.     

Recent developments in cold plasma decontamination technology in the food industry

BackgroundThe advent of the 21^st century has witnessed a growing demand of safe and nutritious foods. The food industry is adopting novel non-thermal food processing technologies. Cold plasma is one such promising non-thermal food processing method which uses charged, highly reactive gaseous molecules and species to inactivate contaminating microorganisms on foods and packaging materials.Scope and approachThe paper gives the reader an overview of the cold plasma technology in food industry. It reviews principles of plasma generation, including mechanisms of action of the process on microorganisms. It also highlights different plasma generation systems, various published results of plasma application to inactivate microorganisms in vitro and in various food products, food packages and equipment surfaces. The challenges of the process, its effects on food quality and the future prospects are highlighted.Key findings and conclusionsThis article aims to review and apprise readers about the important fundamentals and latest trends in the Cold Plasma technology. The on-going studies on plasma technology prove that cold plasma is strongly effective for surface decontamination, with efforts in-progress for liquid processing. The short time of application causes no significant deterioration in food products. Thus, it is an apt alternative processing technology which could also help to counter food allergenicity, seed germination, packaging material printing, waste-water treatment, modify food functionality, extract bio-actives etc. Further research is needed for scaling-up of this process for future commercialization.     

冷等离子体在粮油行业应用研究进展北大核心CSCD

冷等离子体(CP)技术是环境友好的新兴食品非热加工技术,为了促进我国粮油行业研发冷等离子体发生设备,概述了冷等离子体在改善面粉、淀粉及蛋白粉的功能性,减少米饭蒸煮时间,提高籽粒的安全性,降低油脂氢化中反式脂肪酸的生成,降解粮粒真菌毒素及防治储粮害虫等方面的应用研究进展。并提出冷等离子体作用于粮油食品中的机制,包括活性氧和活性氮反应,酸碱度降低学说和生物大分子修饰。冷等离子体处理后粮油食品的pH降低,脂质氧化作用增加,这对设备和工艺研发提出了新要求,今后研究中要规范给出冷等离子体设备处理粮油食品及原料的参数,这对加速冷等离子体技术在粮油行业应用的法规制定具有重要作用。     

低温等离子体技术在肉品保藏及加工中的应用研究进展

低温等离子体作为一种新兴的非热能技术已成为研究热点,该技术具有安全、温和、操作简便以及成本较低等优点,在食品非热加工领域具有广泛的应用前景。低温等离子体在激发过程中能够产生臭氧、单线态氧、超氧阴离子自由基、羟自由基、氮氧化物等活性物质,对肉品中微生物的抑制和亚硝酸盐的产生具有独特的作用。本文概述了低温等离子体的产生方式,分析了其工作效率和影响因素,并在此基础上从抑制微生物生长和替代亚硝酸钠两方面,介绍了低温等离子体技术在肉品保藏及加工中的应用研究进展,同时探讨了低温等离子体对肉品脂肪氧化的影响,并对其应用前景进行展望,为推动低温等离子体技术在肉品研究中的应用和推广提供理论参考。     

低温等离子体技术在食品杀菌中应用的研究进展

低温等离子体技术是一种新兴的非热加工技术,目前已在食品行业中的多个领域得到应用,该技术利用食品周围介质产生光电子、离子和自由基等活性物质,对食品中微生物的抑制和化学农药的降解具有独特的作用。本文以新鲜果蔬、生鲜海鲜、肉及家禽制品等为研究分析对象,系统地论述了低温等离子体的形成机理和技术特点,分析影响其杀菌效率的因素及提高杀菌效率的技术条件,并在此基础上从抑制微生物生长维持食品新鲜度的角度,归纳了低温等离子体技术在新鲜果蔬、生鲜海鲜、肉及家禽制品等的应用研究进展,展望了低温等离子体技术的应用发展趋势,为低温等离子体技术在食品工业中的应用研究提供参考。     

低温等离子体对动物源食品中脂质氧化作用研究进展

低温等离子体作为一种新兴非热杀菌技术, 具有广谱杀菌作用, 在食品杀菌保鲜领域已有广泛的应用研究, 因其含有大量活性自由基,在杀死微生物同时能够促进脂质和蛋白质氧化,对产品品质造成一定影响。本文重点概述了低温等离子体处理对牛肉、鸡肉、猪肉、水产品、油脂和乳脂等产品中脂质氧化作用; 总结了处理时间、处理功率、处理电压、贮藏时间以及样品中不饱和脂肪酸含量等因素对脂质氧化的作用。为降低低温等离子体处理对脂质氧化的促进作用,减弱因脂质氧化对产品品质造成的负面影响,添加抗氧化成为一种有效的途径,因此,本文针对添加天然抗氧化剂降低低温等离子体处理食品中脂质氧化程度的研究内容进行概括总结以及研究前景展望。通过低温等离子体处理条件对动物源食品中脂质氧化影响进行概述, 以及抗氧化措施总结和展望,可为低温等离子体在食品保鲜领域的深入研究以及工业应用提供理论参考。     

Treating lamb’s lettuce with a cold plasma – Influence of atmospheric pressure Ar plasma immanent species on the phenolic profile of Valerianella locusta

The antimicrobial effectiveness of non-thermal plasma is scientifically accepted. Applications can be found in medicinal sterilisation processes. However, the effects of plasma treatments on plant food with regard to nutritional value are not yet sufficiently investigated. To study the interactions of plasma immanent reactive species with secondary plant metabolites, lamb’s lettuce (Valerianella locusta) was exposed to an atmospheric pressure plasma jet. Changes in the phenolic profile were compared to experiments with pure substances to determine the influence of the food matrix. Whereas pure flavonoids showed a strong time-dependent decrease, not originating from photo- or thermodesorption processes, the content of diosmetin in lamb’s lettuce significantly increased. Regarding phenolic acids, plasma exposure led to a strong reduction in lamb’s lettuce, while the concentration of pure monophenols changed little within the same period of time. Treatments with plasma-similar temperatures and UV radiation suggest that due to plasma-reactive species concomitant disintegration of cell membranes and oxidation of released cellular compounds are taking place. Time-dependent changes of the leaf surface morphology due to plasma-induced erosion have been observed by scanning electron microscopy.     

Interactions between proteins and phenolics: effects of food processing on the content and digestibility of phenolic compounds

Phenolic compounds have recently become one of the most interesting topics in different research areas, especially in food science and nutrition due to their health-promoting effects. Phenolic compounds are found together with macronutrients and micronutrients in foods and within several food systems. The coexistence of phenolics and other food components can lead to their interaction resulting in complex formation. This review article aims to cover the effects of thermal and non-thermal processing techniques on the protein–phenolic interaction especially focusing on the content and digestibility of phenolics by discussing recently published research articles. It is clear that the processing conditions and individual properties of phenolics and proteins are the most effective factors in the final content and intestinal fates of phenolic compounds. Besides, thermal and non-thermal treatments, such as high-pressure processing, pulsed electric field, cold plasma, ultrasonication, and fermentation may induce alterations  in those interactions. Still, new investigations are required for different food processing treatments by using a wide range of food products to enlighten new functional and healthier food product design, to provide the optimized processing conditions of foods for obtaining better quality, higher nutritional properties, and health benefits. © 2024 Society of Chemical Industry.     

低温等离子体在农产品加工保藏中应用的研究进展

低温等离子体技术是一种新兴的非热处理技术,具有安全、高效、无毒副作用等特点,在农产品加工、环保、医药以及纺织等领域具有十分广阔的前景。近年来,将低温等离子体技术应用于农产品保藏的研究正在兴起。本文综述了等离子体的分类,分析了低温等离子体灭菌的应用、影响因素以及作用机理,此外还分析了低温等离子体在脱除农残和包装材料中的不同应用研究进展,探讨了低温等离子体用于农产品保藏的优点以及存在的问题,并对低温等离子体技术应用于食品工业的前景进行了展望,为低温等离子体技术在农产品加工中的应用研究提供参考。     

冷等离子体技术对食品组分的影响及其作用机制

冷等离子体作为一种新型的非热加工技术,因其具有安全、绿色、能耗低等优点,在食品加工领域受到广泛关注。冷等离子体使用的气体在电离过程中产生的紫外线、活性物质（如活性氧、活性氮、羟自由基和离子）等会通过辐射/修饰作用使生物大分子发生刻蚀及交联,或对食品组分（脂质、蛋白质、淀粉等）的表面结构和官能团进行修饰,使组分结构发生变化,从而影响食品的品质、功能特性等。本文综述了冷等离子体作用对食品主要组分（蛋白质、脂质、淀粉）、维生素和多酚的影响及其可能的作用机制,并讨论了该技术存在的问题和未来发展的方向,以期为冷等离子体在食品工业的应用提供参考。     

Bacterial spore inactivation induced by cold plasma

ABSTRACT

Cold plasma has emerged as a non-thermal technology for microbial inactivation in the food industry over the last decade. Spore-forming microorganisms pose challenges for microbiological safety and for the prevention of food spoilage. Inactivation of spores induced by cold plasma has been reported by several studies. However, the exact mechanism of spore deactivation by cold plasma is poorly understood; therefore, it is difficult to control this process and to optimize cold plasma processing for efficient spore inactivation. In this review, we summarize the factors that affect the resistance of spores to cold plasma, including processing parameters, environmental elements, and spore properties. We then describe possible inactivation targets in spore cells (e.g., outer structure, DNA, and metabolic proteins) that associated with inactivation by cold plasma according to previous studies. Kinetic models of the sporicidal activity of cold plasma have also been described here. A better understanding of the interaction between spores and cold plasma is essential for the development and optimization of cold plasma technology in food the industry.     

Surface morphology and chemical composition of lamb’s lettuce (Valerianella locusta) after exposure to a low-pressure oxygen plasma

The influence of a low-pressure oxygen glow discharge plasma on secondary metabolites of lamb’s lettuce was examined. After extraction and hydrolysis the compounds were analysed by means of RP-HPLC. Whereas pure compounds showed a time-dependent degradation (flavonoids) or remained unchanged (phenolic acids), the exposure of lamb’s lettuce to the oxygen plasma led to a significant increase of protocatechuic acid, luteolin, and disometin after 120 s treatment time, independent of the applied plasma driving voltage. Contact angle (CA) measurements show an increased wettability of adaxial leaf surfaces after plasma exposure. A successive degradation of epicuticular waxes and cutin of the plant’s epidermis has been indicated by means of FTIR (ATR) and scanning electron microscopy (SEM). These findings suggest that reactive species in the plasma play a crucial role for the observed changes upon exposure to non-thermal plasma.     

Effects of bubble and reactor shape on cold plasma yeast inactivation

Cold plasma is a promising non-thermal technology for inactivating pathogenic and spoilage microorganisms in food by generating various reactive species that damage and inactivate the microorganisms. In this study, a mathematical model was established using COMSOL software to quantitatively describe the process of yeast inactivation by cold plasma under different treatment conditions. The study investigated the effects of discharge voltage, bubble size, and reactor shape on the efficiency of yeast inactivation in apple juice. The results revealed that the discharge voltage significantly influenced yeast inactivation, with a 0.4-fold voltage increase leading to a 53% reduction in inactivation time, achieving a 4-log reduction within 12 min at 21 kV. However, bubble size and reactor shape had no significant impact on the inactivation. The developed model can help to predict the cold plasma inactivation yeast in apple juice, facilitating the design and optimization of plasma-based microbial inactivation in liquid food processing.     

Effects of atmospheric cold plasma and ozone on prebiotic orange juice

In this study, the effect of plasma and ozone treatments on the quality of orange juice was evaluated. The juice was directly and indirectly exposed to a plasma field at 70 kV for different treatment times: 15, 30, 45 and 60 s. For ozone processing, different loads (0.057, 0.128 and 0.230 mg/O₃ mL of juice) were evaluated. After the treatments, the oligosaccharides were quantified by HPLC. The juice pH, color, total phenolic content and total antioxidant activity were also determined. Both processes promoted a partial degradation of the oligosaccharides in the juice. However, the juice maintained an enough amount of oligosaccharides to be classified as a prebiotic food. The phenolic content and antioxidant capacity of the treated samples was also well preserved as the pH and color. Thus, atmospheric cold plasma and ozone are suitable non-thermal alternatives for prebiotic orange juice treatment.Industrial relevanceConsumers are looking for safe food products with high quality. Thus, the food industry is currently considering non-thermal processes as an alternative to reduce the nutrient loss in processed foods. Despite atmospheric cold plasma and ozone are technologies already evaluated as an efficient non-thermal alternative for pathogens inactivation in orange juice, no previous studies on their effects on the oligosaccharides in functional fruit juice was published. This study is of industrial relevance because it demonstrates that after plasma and ozone treatment the overall quality of prebiotic orange juice was preserved and the product maintained its functional appeal.     

Impact of plasma processed air (PPA) on phenolic model systems: Suggested mechanisms and relevance for food applications

Cold plasma is considered to be a novel, non-thermal, chemical-free and eco-friendly disinfection and surface modification technology. Plasma treatment of air to generate the so called plasma processed air (PPA) induces the formation of reactive oxygen (ROS) and nitrogen species (RNS). As a result, PPA has a different chemical composition compared to untreated air and suits therefore as an alternative method for microbial disinfection. However, depending on the product properties of the food matrix and its composition, a number of plasma-induced reactions also need to be taken into consideration.This necessitates also the elucidation and understanding of the basic interactions of plasma species with bioactive compounds. The intention here is to avoid the degradation of these valuable substances and to prevent other undesirable effects in future food related applications.In the present study, the effects of PPA treatment on selected antioxidants such as pyrocatechol and derivatives of hydroxycinnimic acid were investigated in model systems to specify possible reactions induced. Antioxidant capacity, pH value, UV–Vis spectroscopy, RP-HPLC and LC-MS analysis were applied to identify reaction products providing information on possible changes induced in food matrices by PPA treatment.Exposure to PPA caused a perceptible color change towards yellow-brown accompanied by a strong reduction of the pH and the formation of insoluble sediments in the model solutions. The accumulation of nitrate, nitrite, but not of hydrogen peroxide was shown. LC-MS analysis demonstrated the formation of plasma-modified derivatives in all tested systems. The main reactions in liquid model solutions exposed to PPA were attributed to oxidation, nitration and polymerization of the phenolic compounds.     

Novel and emerging technologies used by the U.S. food processing industry

The main purpose of this research was to investigate the extent of novel non-thermal food processing technologies usage in the United States. A survey was conducted to food experts to study the major reasons for using novel technologies, the limitations for not implementing specific technologies, and the main drivers for innovation of non-thermal food processing technologies. The survey study focused on the high-pressure processing, pulsed electric field, pulsed light, irradiation, ultrasound, oscillating magnetic fields, and cold atmospheric plasma technologies. High pressure processing (35.6%) was the most commonly used non-thermal food processing technologies, followed by pulsed electric field (20%). Rapidly increasing novel technologies included cold atmospheric plasma (14.1%) and oscillating magnetic fields (14.1%). More than 70% of the respondents indicated that the main factor for choosing non-thermal food processing technology was better nutrient and sensory properties. High investment (41%) was the major limitation for implementing non-thermal food processing technologies. The results indicated the main drivers for innovation were equipment manufacturers (43.8%) and government research (42.3%). The results emphasized the need for new and improved innovative, non-thermal technologies to provide a balance between safety and minimal processing.Industrial relevanceThis research provides industry with an overview of perceptions food managers, scientists and technologists of novel non-thermal food processing technologies. This research investigated factors that food companies use to implement particular food processing technologies and the limitations prohibit them from using such technologies. There are technologies which are still under development and are currently being conducted to extend the shelf life of certain foods while preserving freshness and natural nutrients. This study investigated technologies currently being used, ones still under development, and the main drivers for innovation of these technologies within the United States.     

Effects of Nonthermal Plasma Technology on Functional Food Components

Understanding the impact of nonthermal plasma (NTP) technology on key nutritional and functional food components is of paramount importance for the successful adoption of the technology by industry. NTP technology (NTPT) has demonstrated marked antimicrobial efficacies with good retention of important physical, chemical, sensory, and nutritional parameters for an array of food products. This paper presents the influence of NTPT on selected functional food components with a focus on low‐molecular‐weight bioactive compounds and vitamins. We discuss the mechanisms of bioactive compound alteration by plasma‐reactive species and classify their influence on vitamins and their antioxidant capacities. The impact of NTP on specific bioactive compounds depends both on plasma properties and the food matrix. Induced changes are mainly associated with oxidative degradation and cleavage of double bonds in organic compounds. The effects reported to date are mainly time‐dependent increases in the concentrations of polyphenols, vitamin C, or increases in antioxidant activity. Also, improvement in the extraction efficiency of polyphenols is observed. The review highlights future research needs regarding the complex mechanisms of interaction with plasma species. NTP is a novel technology that can both negatively and positively affect the functional components in food.     

冷等离子体技术在蛋白质改性中的应用研究进展

蛋白质是人体必需的营养素之一,其营养价值和功能特性决定了加工食品的品质和稳定性。然而天然蛋白质的功能特性往往不能满足现代食品工业的需求,因此通过相应的科学技术改善蛋白质的功能特性显得十分必要。相比于传统改性方法,冷等离子体技术是一种新兴的非热物理改性方法,具有操作温度低、无需外源化学试剂、节约成本等优势,能够最大限度保留蛋白质营养价值的同时改善其功能特性。本文综述了冷等离子体不同产生方式的优缺点以及在食品领域的研究现状,并对冷等离子体技术改善蛋白质功能特性的应用研究进行了系统总结,以期为冷等离子体技术在蛋白质改性方面的应用提供理论支撑。     

Diagnostics of plasma reactive species and induced chemistry of plasma treated foods

Cold plasma is a promising technique that has been tested as a process technology for a range of food commodities, mainly to destroy microorganisms, but also aimed at toxin degradation, enzyme inactivation, residual pesticide degradation and functionalization of food properties. Plasma has already been employed by industry for food packaging material sterilization and surface modification. As most of the current literature on cold plasma in the field of food science is focused on microbial inactivation efficacy, the information about its chemical influences on food is sparse. To better understand the chemical interactions of with plasma, this review focuses on plasma chemistry diagnostics techniques available to characterize the plasma reactive species generated. Equally important is the detection of induced chemistry in the food and here we present approaches to analyze likely reactions with key food bio-molecules. Such analysis will support mechanistic insights involved in these complex chemical reactions (i.e., DNA, lipid and protein) along with potential physical modifications of the food structure. For successful adoption of plasma as a food processing aid it is critical to elucidate these interactions as they have an important role in demonstrating the technology’s safety as a food processing technique along with understanding any effect on food nutrients.     

Non-thermal technologies and its current and future application in the food industry: a review

In recent years, consumers have been demanding convenient and healthy foods which have ‘fresh-like’ characteristics while still being safe and a long shelf-life. These requirements are hard to achieve using existing traditional thermal food processing technologies and the innovative new food process and preservation technologies based on thermal processing systems are needed. However, non-thermal technologies in food processing do not generate high temperature and use short treatment times. This means that the nutritional components of foodstuffs are better retained, and the sensory properties of foods are less changed compared with traditional thermal processing. The aim of this review was to present non-thermal technologies applications and its mechanism in food industry in recently, and to explore the potential application prospects of combining non-thermal treatments applied in food industry because it not only could overcomes the drawback of single technology, but also can enhances the processing efficiency at lower treatment intensity.