Cold Plasma‐Mediated Treatments for Shelf Life Extension of Fresh Produce: A Review of Recent Research Developments

Fresh produce, like fruits and vegetables, are important sources of nutrients and health‐promoting compounds. However, incidences of foodborne outbreaks associated with fresh produce often occur; it is thus important to develop and expand decay‐control technologies that can not only maintain the quality but can also control the biological hazards in postharvest, processing, and storage to extend their shelf life. It is under such a situation that plasma‐mediated treatments have been developed as a novel nonthermal processing tool, offering many advantages and attracting much interest from researchers and the food industry. This review summarizes recent developments of cold plasma technology and associated activated water for shelf life extension of fresh produce. An overview of plasma generation and its physical–chemical properties as well as methods for improving plasma efficiency are first presented. Details of using the technology as a nonthermal agent in inhibiting spoilage and pathogenic microorganisms, inactivating enzymes, and modifying the barrier properties or imparting specific functionalities of packaging materials to extend shelf life of food produce are then reviewed, and the effects of cold plasma‐mediated treatment on microstructure and quality attributes of fresh produce are discussed. Future prospects and research gaps of cold plasma are finally elucidated. The review shows that atmospheric plasma‐mediated treatments in various gas mixtures can significantly inhibit microorganisms, inactive enzyme, and modify packaging materials, leading to shelf life extension of fresh produce. The quality attributes of treated produce are not compromised but improved. Therefore, plasma‐mediated treatment has great potential and values for its application in the food industry.     

Mild processing of seafood—A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.     

Nonthermal Technologies for Fruit and Vegetable Juices and Beverages: Overview and Advances

In recent years, there has been a growing interest in the design of novel nonthermal processing systems that minimally modify sensory, nutritional, and functional properties of fruit and vegetable juices and beverages. The benefits of nonthermal treatments are strongly dependent on the food matrix. Thus, an understanding of the effects that these technologies exert on the properties of juices and beverages is important to design and optimize technological parameters to produce value‐added products. This review covers research on nonthermal electrical treatments, high pressure processing, ultrasound, radiation processing, inert gas treatments, cold plasma, and membrane processing. Advances towards optimization of processing conditions, and combined technologies approaches have been also extensively reviewed. This information could be useful to: (1) manage processing systems and optimize resources; (2) preserve nutritional value and organoleptic properties, and (3) provide processing conditions for validation of these technologies at the industrial scale.     

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.     

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.     

Radiation processing to improve the quality of fishery products.

Extensive investigations, worldwide, in the last 4 decades have shown the benefits of radiation processing for the preservation and microbial quality improvement of seafoods. In the present review, the various factors determining the quality of seafoods are first presented. The basic principles underlying the effects of ionizing radiation and specific effects on food constituents such as proteins, amino acids, lipids, vitamins, and tissue enzymes are discussed. Data on radiation processing of seafoods are reported and discussed with respect to shelf life enhancement under refrigeration by control of bacteria causing spoilage, radiation sensitivity of pathogenic microorganisms and parasites of public health significance and their elimination in fresh and frozen fishery products, control of insect disinfestation in dried fishery products, influence of irradiation on nutritional and sensory quality attributes, detection of irradiation treatment, economics, and international status.     

Trends in microbial control techniques for poultry products

Fresh poultry meat and poultry products are highly perishable foods and high potential sources of human infection due to the presence of several foodborne pathogens. Focusing on the microbial control of poultry products, the food industry generally implements numerous preventive measures based on the Hazard Analysis and Critical Control Points (HACCP) food safety management system certification together with technological steps, such as refrigeration coupled to modified atmosphere packaging that are able to control identified potential microbial hazards during food processing. However, in recent years, to meet the demand of consumers for minimally processed, high-quality, and additive-free foods, technologies are emerging associated with nonthermal microbial inactivation, such as high hydrostatic pressure, irradiation, and natural alternatives, such as biopreservation or the incorporation of natural preservatives in packaging materials. These technologies are discussed throughout this article, emphasizing their pros and cons regarding the control of poultry microbiota and their effects on poultry sensory properties. The discussion for each of the preservation techniques mentioned will be provided with as much detail as the data and studies provided in the literature for poultry meat and products allow. These new approaches, on their own, have proved to be effective against a wide range of microorganisms in poultry meat. However, since some of these emergent technologies still do not have full consumer's acceptability and, taking into consideration the hurdle technology concept for poultry processing, it is suggested that they will be used as combined treatments or, more frequently, in combination with modified atmosphere packaging.     

Food Packaging: A Comprehensive Review and Future Trends

Innovations in food packaging systems will help meet the evolving needs of the market, such as consumer preference for “healthy” and high‐quality food products and reduction of the negative environmental impacts of food packaging. Emerging concepts of active and intelligent packaging technologies provide numerous innovative solutions for prolonging shelf‐life and improving the quality and safety of food products. There are also new approaches to improving the passive characteristics of food packaging, such as mechanical strength, barrier performance, and thermal stability. The development of sustainable or green packaging has the potential to reduce the environmental impacts of food packaging through the use of edible or biodegradable materials, plant extracts, and nanomaterials. Active, intelligent, and green packaging technologies can work synergistically to yield a multipurpose food‐packaging system with no negative interactions between components, and this aim can be seen as the ultimate future goal for food packaging technology. This article reviews the principles of food packaging and recent developments in different types of food packaging technologies. Global patents and future research trends are also discussed.     

Evaluation of different varieties of cauliflower for minimal processing

The impact of minimal processing technology on the sensory quality and the growth of micro‐organisms in eight varieties of cauliflower packaged in four different films (one PVC and three P‐Plus) was measured and quantified during more than 25 days of storage at 4 °C. Other important parameters such as weight loss and gas concentration in the packages were also determined. The composition of the atmosphere in the packages of minimally processed cauliflower depended on both the permeability of the film used for the packaging and the variety of cauliflower. When establishing shelf‐life, loss of sensory quality was the deciding factor rather than loss of microbiological quality. The initial microbial load proved more important than the composition of the atmosphere inside the packages. In sensory evaluation the most important aspect was colour. In instrumental evaluation, coordinate b* was the main means of estimating shelf‐life. The combination of P‐Plus 120 film and varieties of cauliflower of large size and great vigour allowed the atmosphere inside the packages to have an O₂ level below 10% and a CO₂ level above 10%. That atmosphere composition proved essential for maintaining the sensory quality of minimally processed cauliflower. In these conditions, samples attained a shelf‐life of more than 25 days. However, the different behaviours of the cauliflower varieties make it necessary to establish particular packaging conditions. The use of less permeable films than those used in this study, or the use of actively modified atmospheres, could be an alternative for those varieties that require special packaging conditions when processed using this technology. Copyright © 2006 Society of Chemical Industry     

Physiochemical and Microbiological Quality of Lightly Processed Salmon (Salmo salar L.) Stored Under Modified Atmosphere

Low‐temperature cooking, such as sous vide, has become a favored method for processing seafood. For this method to be applicable for retail products, combinations with other processing steps are needed to keep the products safe and durable while maintaining high quality. The present experiments were designed to investigate the influence of low‐temperature treatment (40, 50, or 60 °C) in combination with various packaging technologies (modified atmosphere [MA] or soluble gas stabilization [SGS]) on both the microbial growth and the physiochemical quality. Salmon loins were either kept natural or inoculated with Listeria innocua prior to drying (16 to 18 hr) in either 100% CO₂ (SGS) or atmospheric air (MA packaging). All samples were sous vide treated, repackaged in MA, and stored at 4 °C for 24 days. The results showed shelf life to be significantly improved with the implementation of SGS, by prolonging the lag‐phase and slowing the growth rate of both naturally occurring and inoculated bacteria. Variations in packaging technology did not significantly influence any of the tested quality parameters, including drip loss, surface color, and texture. Growing consumer demand for lightly processed seafood products makes Listeria spp. an increasing problem. The present experiment, however, has shown that it is possible to lower processing temperatures to as little as 40 or 50 °C and still obtain inhibition of Listeria, but with improved chemical quality compared to traditional processing.     

Nonthermal Food Processing Alternatives and Their Effects on Taste and Flavor Compounds of Beverages

Food drinks are normally processed to increase their shelf-life and facilitate distribution before consumption. Thermal pasteurization is quite efficient in preventing microbial spoilage of many types of beverages, but the applied heat may also cause undesirable biochemical and nutritious changes that may affect sensory attributes of the final product. Alternative methods of pasteurization that do not include direct heat have been investigated in order to obtain products safe for consumption, but with sensory attributes maintained as unchanged as possible. Food scientists interested in nonthermal food preservation technologies have claimed that such methods of preserving foods are equally efficient in microbial inactivation as compared with conventional thermal means of food processing. Researchers in the nonthermal food preservation area also affirm that alternative preservation technologies will not affect, as much as thermal processes, nutritional and sensory attributes of processed foods. This article reviews research in nonthermal food preservation, focusing on effects of processing of food drinks such as fruit juices and dairy products. Analytical techniques used to identify volatile flavor-aroma compounds will be reviewed and comparative effects for both thermal and nonthermal preservation technologies will be discussed.     

New strategies for minimally processed cactus pear packaging

This work presents a preliminary study on the packaging procedures to prolong the shelf life of minimally processed cactus pears. In particular, different packaging strategies were tested by combining coating and hydro-gels to different polymeric materials. Monitoring headspace gas concentrations, viable cell load of main spoilage microorganisms, sensory characteristics and weight loss, the quality decay in each packaging system was assessed. Results showed that the immersion of fresh-cut fruit into both hydro-gels strongly reduced the shelf life, most probably due to water migration from the surrounding hydro-gel to the crop. On the contrary, the coating prolonged the shelf life of the minimally processed fruit to about 13 days, corresponding to an increase of about 40%, compared to the control sample. Results also suggested that the barrier properties of the selected films did not affect greatly the quality of the coated fresh-cut produce.Industrial relevanceThe market of ready-to-eat fruit has grown rapidly in recent years. As a consequence, there is an emergent call for finding new preservation strategies to prolong the shelf life of minimally processed food, without compromising human and environmental safety. The results of this work dealing with minimally processed cactus pears represented an interesting goal with potential industrial applications. In fact, this paper combined the effectiveness of a natural coating applied to fresh-cut fruit to the performance of a bio-based polymeric packaging film.     

The Potential of the Incorporation of Essential Oils and Their Individual Constituents to Improve Microbial Safety in Juices: A Review

The juice sector is one of the fastest growing sectors in the food industry. Although juices are important because of their nutritional value and convenience, their composition and physicochemical properties affect their microbiological safety and overall quality during their shelf‐life. Furthermore, the thermal process classically applied in juices partially reduces the occurring microflora, and the use of chemical additives is perceived negatively by consumers. For these reasons, researchers have proposed the use of nonthermal technologies as antimicrobial preservatives in juices. This paper covers the recent literature on the use of essential oils (EOs) and the individual constituents (ICs) found therein, used alone or in combination with other emerging technologies, for the preservation of juices. From this perspective, this paper discusses the growing importance of the use of EOs and their ICs, either alone or in association with other emerging technologies, in juices and their effects on the safety and physicochemical and sensory quality attributes of these products. The results of papers currently available in the literature reveal that EOs and their ICs are promising alternatives to achieve microbial safety and stability in juices. However, extensive studies considering the effects of each EO or IC on sensory characteristics, primarily taste and aroma, are still needed to establish each of these substances/compounds as feasible preservatives for use in juices. Finally, further studies could focus on the combination of low amounts of EOs or ICs with other nonthermal technologies to achieve a balance between the microbial safety and sensory acceptability of juices.     

Suitability,efficiency and microbiological safety of novel physical technologies for the processing of ready‐to‐eat meals,meats and pumpable products

Consumer studies and market reports show an increase in consumption of ready‐to‐eat (RTE) foods. Although conventional processing technologies can in most cases produce safe products, they can also lead to the degradation of nutritional compounds and negatively affect quality characteristics. Consumers strongly prefer food that is minimally processed with the maximum amount of health‐promoting substances. Novel processing technologies as pre‐ or post‐treatment decontamination methods or as substitutes of conventional technologies have the potential to produce foods that are safe, rich in nutrient content and with superior organoleptic properties. Combining novel with conventional processes can eliminate potential drawbacks of novel technologies. This review examines available scientific information and critically evaluates the suitability and efficiency of various novel thermal and nonthermal technologies in terms of microbial safety, quality as well as nutrient content on the production of RTE meals, meats and pumpable products.     

Flavonoids in fruits and vegetables after thermal and nonthermal processing: A review

ABSTRACT

Consumers currently demand more nutritious food, which is minimally processed and naturally produced. Flavonoids are one of the major plant metabolites found throughout the plant kingdom, especially in fruits and vegetables. Flavonoids exert tremendous positive effects on health and protect against various diseases. Fruits and vegetables are difficult to store for a long period, owing to their perishable nature even at low temperatures. Therefore, processing is necessary to prolong their shelf lives and increase nutritional values. Thermal processing has been used in the food sector since ancient times. However, nonthermal processing has become more attractive to consumers and product developers recently, owing to the retention of beneficial health properties after nonthermal processing. The present review will address the effects of thermal and nonthermal processing methods such as blanching, drying, high-pressure processing, ultrasound, pulsed electric field, and ultraviolet irradiation on total and individual flavonoid content in fruits and vegetables. In addition, this text will elucidate the stability characteristics as well as bioavailability, cytotoxicity, and transformations of flavonoids during thermal and nonthermal treatments.     

Impact of irradiation on fish and seafood shelf life: a comprehensive review of applications and irradiation detection

Irradiation is one of the most important and effective methods towards food preservation despite the consumer lack of trust and aversion towards this method. Irradiation effectiveness greatly depends on the dose provided to food. This review aims at summarizing all available information regarding the impact of irradiation dose on the shelf life and microflora and sensory and physical properties of fish, shellfish, molluscs, and crustaceans. The synergistic effect of irradiation in conjunction with other techniques such as salting, smoking, freezing, and vacuum packaging was also reported. Another issue covered within the frame of this review is the detection (comparison of methods in terms of their effectiveness and validity) of irradiated fish and seafood. The information related to fish and seafood irradiation and its detection is presented by means of 11 comprehensive tables and 9 figures.     

Microbiological and Sensorial Quality Assessment of Ready-to-Cook Seafood Products Packaged under Modified Atmosphere

ABSTRACT:  The effects of modified atmosphere packaging (MAP) (30:40:30 O₂:CO₂:N₂ and 5:95 O₂:CO₂) on the quality of 4 ready-to-cook seafood products were studied. In particular, the investigation was carried out on hake fillets, yellow gurnard fillets, chub mackerel fillets, and entire eviscerated cuttlefish. Quality assessment was based on microbiological and sensorial indices determination. Both packaging gas mixtures contributed to a considerable slowing down of the microbial and sensorial quality loss of the investigated seafood products. Results showed that sensorial quality was the subindex that limited their shelf life. In fact, based primarily on microbiological results, samples under MAP remained acceptable up to the end of storage (that is, 14 d), regardless of fish specie. On the other hand, results from sensory analyses showed that chub mackerel fillets in MAP were acceptable up to the 6th storage d, whilst hake fillets, yellow gurnard fillets, and entire cuttlefish became unacceptable after 10 to 11 d. However, compared to control samples, an increase in the sensorial shelf life of MAP samples (ranging from about 95% to 250%) was always recorded.
Practical Application: Modified atmosphere packaging (MAP) is an inexpensive and uncomplicated method of extending shelf life of packed seafood. It could gain great attention from the fish industrial sector due to the fact that MAP is a practical and economic technique, realizable by small technical expedients. Moreover, there is great attention from the food industry and retailers to react to the growing demand for convenience food, thus promoting an increase in the assortments of ready-to-cook seafood products.     

Microbiological aspects and shelf life of processed seafood products

BACKGROUND: Fresh fish and seafoods are very perishable products mainly owing to microbial activity of specific spoilage micro‐organisms. Application of hurdle technology leads to a variety of processed products with extended shelf life. In this study, sensory evaluation and microbiological analysis were carried out on 17 processed seafood products stored at 4 °C to determine their shelf life and the predominant spoilage micro‐organisms. RESULTS: Shelf life determined by sensory analysis varied from 66 to 180 days depending on the product. The cause of spoilage for most of the products was the development of off‐flavours/off‐odours, while two products were rejected owing to oil discolouration. Pseudomonads were in most cases below detection limit. H₂S‐producing bacteria, Brochothrix thermosphacta and Enterobacteriaceae were below detection limit throughout the experiment. The predominant spoilage micro‐organisms were lactic acid bacteria and yeasts. Hygiene indicators such as Staphylococcus spp. and total coliforms were also below detection limit in all samples. CONCLUSION: Primarily the initial pH and secondarily the NaCl content determined shelf life duration. Under the applied conditions, lactic acid bacteria and yeasts predominated. The contribution of chemical oxidation and/or autolysis to spoilage and shelf life might be important for most of the products. © 2012 Society of Chemical Industry     

Effects of Ultraviolet Light and High‐Pressure Processing on Quality and Health‐Related Constituents of Fresh Juice Products

Fresh juices are highly popular beverages in the global food market. They are perceived as wholesome, nutritious, all‐day beverages. For a fast growing category of premium juice products such as cold‐pressed juices, minimal‐processing nonthermal techniques such as ultraviolet (UV) light and high‐pressure processing (HPP) are expected to be used to extend shelf‐life while retaining physicochemical, nutritional, and sensory characteristics with reduced microbial loads. Also, UV light and HPP are approved by regulatory agencies and recognized as one of the simplest and very environmentally friendly ways to destroy pathogenic organisms. One of the limitations to their more extensive commercial application lies in the lack of comparative effects on nutritional and quality‐related compounds in juice products. This review provides a comparative analysis using 92 studies (UV light: 42, HPP: 50) mostly published between 2004 and 2015 to evaluate the effects of reported UV light and HPP processing conditions on the residual content or activity of bioactive compounds such as vitamins, polyphenols, antioxidants, and oxidative enzymes in 45 different fresh fruit and vegetable juices (low‐acid, acid, and high‐acid categories). Also, the effects of UV light and HPP on color and sensory characteristics of juices are summarized and discussed.     

Current topics in active and intelligent food packaging for preservation of fresh foods

The purpose of this review is to provide an overview of current packaging systems, e.g. active packaging and intelligent packaging, for various foods. Active packaging, such as modified atmosphere packaging (MAP), extends the shelf life of fresh produce, provides a high‐quality product, reduces economic losses, including those caused by delay of ripening, and improves appearance. However, in active packaging, several variables must be considered, such as temperature control and different gas formulations with different product types and microorganisms. Active packaging refers to the incorporation of additive agents into packaging materials with the purpose of maintaining or extending food product quality and shelf life. Intelligent packaging is emerging as a potential advantage in food processing and is an especially useful tool for tracking product information and monitoring product conditions. Moreover, intelligent packaging facilitates data access and information exchange by altering conditions inside or outside the packaging and product. In spite of these advantages, few of these packaging systems are commercialized because of high cost, strict safety and hygiene regulations or limited consumer acceptance. Therefore more research is needed to develop cheaper, more easily applicable and effective packaging systems for various foods. © 2015 Society of Chemical Industry