Combining nonthermal technologies to control foodborne microorganisms

Novel nonthermal processes, such as high hydrostatic pressure (HHP), pulsed electric fields (PEFs), ionizing radiation and ultrasonication, are able to inactivate microorganisms at ambient or sublethal temperatures. Many of these processes require very high treatment intensities, however, to achieve adequate microbial destruction in low-acid foods. Combining nonthermal processes with conventional preservation methods enhances their antimicrobial effect so that lower process intensities can be used. Combining two or more nonthermal processes can also enhance microbial inactivation and allow the use of lower individual treatment intensities. For conventional preservation treatments, optimal microbial control is achieved through the hurdle concept, with synergistic effects resulting from different components of the microbial cell being targeted simultaneously. The mechanisms of inactivation by nonthermal processes are still unclear; thus, the bases of synergistic combinations remain speculative. This paper reviews literature on the antimicrobial efficiencies of nonthermal processes combined with conventional and novel nonthermal technologies. Where possible, the proposed mechanisms of synergy is mentioned.     

Inactivation of foodborne pathogens by the synergistic combinations of food processing technologies and food‐grade compounds

There is a need to develop food processing technologies with enhanced antimicrobial capacity against foodborne pathogens. While considering the challenges of adequate inactivation of pathogenic microorganisms in different food matrices, the emerging technologies are also expected to be sustainable and have a minimum impact on food quality and nutrients. Synergistic combinations of food processing technologies and food‐grade compounds have a great potential to address these needs. During these combined treatments, food processes directly or indirectly interact with added chemicals, intensifying the overall antimicrobial effect. This review provides an overview of the combinations of different thermal or nonthermal processes with a variety of food‐grade compounds that show synergistic antimicrobial effect against pathogenic microorganisms in foods and model systems. Further, we summarize the underlying mechanisms for representative combined treatments that are responsible for the enhanced microbial inactivation. Finally, regulatory issues and challenges for further development and technical transfer of these new approaches at the industrial level are also discussed.     

Advances in innovative processing technologies for microbial inactivation and enhancement of food safety – pulsed electric field and low-temperature plasma

The need for enhancing microbial food safety and quality, without compromising the nutritional, functional and sensory characteristics of foods, has created an increasing world-wide interest in low-temperature innovative processes for food preservation. In contrast, to the traditional thermal processes, these emerging technologies are predominantly reliant on physical processes, including high hydrostatic pressures, pulsed electric fields and low-temperature plasmas that inactivate microorganisms at ambient or moderately elevated temperatures and short treatment times. The current review presents the latest developments in the two most recent of these technologies, pulsed electric field and low-temperature plasma treatments for food preservation and disinfection of food contact surfaces.     

Intervention Technologies for Ensuring Microbiological Safety of Meat: Current and Future Trends

Abstract: This article reviews current and future techniques that are applied in the meat industry to ensure product safety. Consumer demand for high‐quality food and raised economic standards have triggered the development of emergent technologies to replace traditional well‐established preservation processes. Some promising nonthermal and thermal technologies, such as chemical and biological interventions, high hydrostatic pressure (HHP), irradiation, active packaging, natural antimicrobials and microwave, radiofrequency, and steam pasteurization, are under consideration for the preservation of meat products. All these alternative technologies are designed to be mild, energy‐conserving, environmentally friendly, and maintaining natural appearance and flavor, while eliminating pathogens and spoilage microorganisms. Their combination, as in the hurdle theory, may improve their effectiveness for decontamination. The objective of this article is to reflect on the possibilities and especially the limitations of the previously mentioned technologies.     

The inactivation of Salmonella by cold atmospheric plasma treatment

The need to fulfill consumer demand for fresh products without compromising microbial food safety and quality has increased the interest of the food industry in low-temperature innovative processes for food preservation. Compared to thermal processing, these emerging technologies rely on physical processes, such as high hydrostatic pressure, ionizing radiation, ultrasonication, pulsed electric fields, ultraviolet radiation and cold plasmas that are able to inactivate microorganisms at ambient or sublethal temperatures. This latter treatment is one of the more promising food preservation technologies. In this review we survey the main factors affecting the sensitivity and resistance of Salmonella to cold atmospheric gas plasmas. A more complete understanding of the factors involved in inactivation by this emerging technology will enhance its implementation in food preservation.     

Effect of nonthermal treatments on selected natural food pigments and color changes in plant material

In recent years, traditional high-temperature food processing is continuously being replaced by nonthermal processes. Nonthermal processes have a positive effect on food quality, including color and maintaining natural food pigments. Thus, this article describes the influence of nonthermal, new, and traditional treatments on natural food pigments and color changes in plant materials. Characteristics of natural pigments, such as anthocyanins, betalains, carotenoids, chlorophylls, and so forth available in the plant tissue, are shortly presented. Also, the characteristics and mechanism of nonthermal processes such as pulsed electric field, ultrasound, high hydrostatic pressure, pulsed light, cold plasma, supercritical fluid extraction, and lactic acid fermentation are described. Furthermore, the disadvantages of these processes are mentioned. Each treatment is evaluated in terms of its effects on all types of natural food pigments, and the possible applications are discussed. Analysis of the latest literature showed that the use of nonthermal technologies resulted in better preservation of pigments contained in the plant tissue and improved yield of extraction. However, it is important to select the appropriate processing parameters and to optimize this process in relation to a specific type of raw material.     

Quality-Related Enzymes in Plant-Based Products: Effects of Novel Food-Processing Technologies Part 3: Ultrasonic Processing

High-power ultrasound is a versatile technology which can potentially be used in many food processing applications including food preservation. This is part 2 of a series of review articles dealing with the effectiveness of nonthermal food processing technologies in food preservation focusing on their effect on enzymes. Typically, ultrasound treatment alone does not efficiently cause microbial or enzyme inactivation sufficient for food preservation. However, combined with mild heat with or without elevated pressure (P ≤ 500 kPa), ultrasound can effectively inactivate enzymes and microorganisms. Synergistic effects between ultrasound and mild heat have been reported for the inactivation of both enzymes and microorganisms. The application of ultrasound has been shown to enhance the rate of inactivation of quality degrading enzymes including pectin methylesterase (PME), polygalacturonase (PG), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) at mild temperature by up to 400 times. Moreover, ultrasound enables the inactivation of relatively heat-resistant enzymes such as tomato PG1 and thermostable orange PME at mild temperature conditions. The extent to which ultrasound enhances the inactivation rate depends on the type of enzyme, the medium in which the enzyme is suspended, and the processing condition including frequency, ultrasonic intensity, temperature, and pressure. The physical and chemical effects of cavitation are considered to be responsible for the ultrasound-induced inactivation of enzymes, although the dominant mechanism depends on the structure of the enzyme.     

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.     

Nonthermal physical technologies to decontaminate and extend the shelf-life of fruits and vegetables: Trends aiming at quality and safety

Minimally processed fruits and vegetables are one of the major growing sectors in food industry. This growing demand for healthy and convenient foods with fresh-like properties is accompanied by concerns surrounding efficacy of the available sanitizing methods to appropriately deal with food-borne diseases. In fact, chemical sanitizers do not provide an efficient microbial reduction, besides being perceived negatively by the consumers, dangerous for human health, and harmful to the environment, and the conventional thermal treatments may negatively affect physical, nutritional, or bioactive properties of these perishable foods. For these reasons, the industry is investigating alternative nonthermal physical technologies, namely innovative packaging systems, ionizing and ultraviolet radiation, pulsed light, high-power ultrasound, cold plasma, high hydrostatic pressure, and dense phase carbon dioxide, as well as possible combinations between them or with other preservation factors (hurdles). This review discusses the potential of these novel or emerging technologies for decontamination and shelf-life extension of fresh and minimally processed fruits and vegetables. Advantages, limitations, and challenges related to its use in this sector are also highlighted.     

Food processing by high hydrostatic pressure

The use of high hydrostatic pressures (HHP) for food processing is finding increased application within the food industry. One of the advantages of this technology is that because it does not use heat, sensory, and nutritional attributes of the product remain virtually unaffected, thus yielding products with better quality than those processed traditional methods. HHP have the ability to inactivate microorganisms as well as enzymes responsible for shortening the life of a product. In addition to lengthening the shelf-life of food products, HHP can modify functional properties of components such as proteins, which in turn can lead to the development of new products. Equipment for large-scale production of HHP processed products are commercially available nowadays. Guacamole, sliced ham, oysters, and fruit juices are some of the products currently available on the market. HHP technology is one of the most promising nonthermal processes.     

Application of nonthermal processing technologies in extracting and modifying polysaccharides: A critical review

Polysaccharides are natural polymer compounds widely distributed in plants, animals, and microorganisms, most of which have a broad spectrum of biological activities to promote human health. They could also be used as texture modifiers in food industry due to their excellent rheological and mechanical properties. Many researchers have shown that nonthermal processing technologies have numerous advantages, such as high extraction efficiency, short extraction time, and environmental friendliness, in the extraction of polysaccharides compared with the traditional extraction methods. Moreover, nonthermal technologies could effectively change the physicochemical properties and structural characteristics of polysaccharides to improve their biological activities or processing properties. Therefore, a comprehensive summary about the extraction and modification of polysaccharides by nonthermal technologies, including ultrasound, high hydrostatic pressure, pulsed electric fields, and cold plasma, was provided in this review. In particular, the underlying mechanisms, processing operations, and current application status of these technologies were discussed. In addition, the applications of combining nonthermal techniques with other technological methods in polysaccharide extraction and modification were briefly introduced.     

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.     

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.     

Combination of Pulsed Electric Fields with Other Preservation Techniques

Pulsed electric field (PEF) is a promising nonthermal treatment for liquid foods with antimicrobial activity at ambient temperature. According to the hurdle concept, the combination of PEF with other preservation methods may enhance cell death. The joint effect of PEF with the addition of antimicrobial compounds of natural origin, such as nisin, has received special attention, although other emerging nonthermal techniques, such as the use of high-pressure carbon dioxide, have also been considered. Moreover, the bactericidal action resulting from the simultaneous application of PEF and conventional thermal treatments suggests the possibility of lowering the intensity of heating while maintaining microbial acceptance. This review analyses the literature on antimicrobial strategies that combine PEF with nonthermal and traditional preservation methods. The variables affecting cell death produced by those combined treatments and their mechanisms of synergy are considered. Commercialization of PEF in combination with other technologies may be possible due to its improved antimicrobial effect.     

Principles and recent applications of novel non-thermal processing technologies for the fish industry—a review

Thermal treatment is a traditional method for food processing, which can kill microorganisms but also lead to physicochemical and sensory quality damage, especially to temperature-sensitive foods. Nowadays consumers’ increasing interest in microbial safety products with premium appearance, flavor, great nutritional value and extended shelf-life has promoted the development of emerging non-thermal food processing technologies as alternative or substitution to traditional thermal methods. Fish is an important and world-favored food but has a short shelf-life due to its extremely perishable characteristic, and the microbial spoilage and oxidative process happen rapidly just from the moment of capture, making it dependent heavily on post-harvest preservation. The applications of novel non-thermal food processing technologies, including high pressure processing (HPP), ultrasound (US), pulsed electric fields (PEF), pulsed light (PL), cold plasma (CP) and ozone can extend the shelf-life by microbial inactivation and also keep good sensory quality attributes of fish, which is of high interest for the fish industry. This review presents the principles, developments of emerging non-thermal food processing technologies, and also their applications in fish industry, with the main focus on microbial inactivation and sensory quality. The promising results showed great potential to keep microbial safety while maintaining organoleptic attributes of fish products. What’s more, the strengths and weaknesses of these technologies are also discussed. The combination of different food processing technologies or with advanced packaging methods can improve antimicrobial efficacy while not significantly affect other quality properties under optimized treatment.     

Nonthermal Processes for Shelf‐Life Extension of Seafoods: A Revisit

For the past two decades, consumer demand for minimally processed seafoods with good sensory acceptability and nutritive properties has been increasing. Nonthermal food processing and preservation technologies have drawn the attention of food scientists and manufacturers because nutritional and sensory properties of such treated foods are minimally affected. More importantly, shelf‐life is extended as nonthermal treatments are capable of inhibiting or killing both spoilage and pathogenic organisms. They are also considered to be more energy‐efficient and to yield better quality when compared with conventional thermal processes. This review provides insight into the nonthermal processing technologies currently used for shelf‐life extension of seafoods. Both pretreatments such as acidic electrolyte water and ozonification and processing technologies, including high hydrostatic pressurization, ionizing radiation, cold plasma, ultraviolet light, and pulsed electric fields, as well as packaging technology, particularly modified atmosphere packaging, have been implemented to lower the microbial load in seafood. Thus, those technologies may be the ideal approach for the seafood industry, in which prime quality is maintained and safety is assured for consumers.     

Application of High-Intensity Pulsed Electrical Fields in Food Processing

High-intensity pulsed electric fields (HIPEF) treatment is gaining popularity as a nonthermal processing technology due to its instant penetration characteristics and short processing time. It is evolving as a potential alternative to other thermal and chemical unit operations in food processing. In recent years, numerous research groups have demonstrated the possibility of inactivation of a range of microorganisms and food quality-related enzymes. This article focuses on the potential to use the HIPEF treatment as a preservation technology and as an adjunct to other processing steps, such as extraction, osmotic dehydration, air dehydration, and rehydration.     

Application of High-Intensity Pulsed Electrical Fields in Food Processing

High-intensity pulsed electric fields (HIPEF) treatment is gaining popularity as a nonthermal processing technology due to its instant penetration characteristics and short processing time. It is evolving as a potential alternative to other thermal and chemical unit operations in food processing. In recent years, numerous research groups have demonstrated the possibility of inactivation of a range of microorganisms and food quality-related enzymes. This article focuses on the potential to use the HIPEF treatment as a preservation technology and as an adjunct to other processing steps, such as extraction, osmotic dehydration, air dehydration, and rehydration.     

Molecular Dynamics Simulation for Mechanism Elucidation of Food Processing and Safety: State of the Art

Molecular dynamics (MD) simulation is a useful technique to study the interaction between molecules and how they are affected by various processes and processing conditions. This review summarizes the application of MD simulations in food processing and safety, with an emphasis on the effects that emerging nonthermal technologies (for example, high hydrostatic pressure, pulsed electric field) have on the molecular and structural characteristics of foods and biomaterials. The advances and potential projection of MD simulations in the science and engineering aspects of food materials are discussed and focused on research work conducted to study the effects of emerging technologies on food components. It is expected by showing key case studies that it will stir novel developments as a valuable tool to study the effects of emerging food technologies on biomaterials. This review is useful to food researchers and the food industry, as well as researchers and practitioners working on flavor and nutraceutical encapsulations, dietary carbohydrate product developments, modified starches, protein engineering, and other novel food applications.