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

UV-B exposure reduces the activity of several cell wall-dismantling enzymes and affects the expression of their biosynthetic genes in peach fruit (Prunus persica L., cv. Fairtime, melting phenotype)

Softening processes after ripening are a major factor contributing to the perishability of fleshy fruit and, together with mechanical damage, represent the onset of physiological decay. Softening involves multiple co-ordinated events leading to modifications of the cell wall architecture. Several studies described that UV-B radiation positively affects both the nutraceutical and aesthetical qualities of fruit. However, very few studies investigated the effect of UV-B irradiation on the activity of cell wall-related enzymes. This research aimed at studying how different UV-B treatments (10 min and 60 min) affect the activity of cell wall-modifying enzymes (pectin methylesterase, polygalacturonase and β-galactosidase) together with the expression of some of their isoforms up to 36 h after UV-B treatment of peach (cv. Fairtime, melting phenotype) fruit. Results revealed that UV-B radiation did not affect the soluble solid content and the titratable acidity, two important parameters influencing consumers' choice and taste. In contrast, UV-B was effective at reducing the loss of firmness 24 h after the 60 min irradiation. Generally, a lower activity of the hydrolytic enzymes compared to untreated fruit was observed, regardless of the UV-B dose. However, gene expression did not reflect the corresponding enzymatic activity. Based on these results, UV-B irradiation might be a successful tool in reducing the loss of firmness of peach fruit during post-harvest, thus improving their quality and shelf-life.

Effects of high hydrostatic pressure on physico-chemical and structural properties of two pumpkin species

The effects of high pressure treatments (200, 400, 600 MPa for 5 min) and a thermal treatment (85 °C for 5 min) were evaluated on cubes of two pumpkin species (Cucurbita maxima L. var. Delica and Cucurbita moschata Duchesne var. Butternut) up to 2 months of refrigerated storage. Increasing the pressure, small parenchyma cells from the pumpkin tissue exhibited collapses and separations, especially for Butternut. This species showed a lower hardness than Delica at time 0. For both species, 400 MPa and thermal treatment were the most effective in the inactivation of pectinmethylesterase, which reactivated after 2 months, especially for Butternut. Colorimetric parameters decreased after all treatments. Antioxidant activity resulted affected by pressure, showing a significant increase during storage especially for the samples treated at 200 MPa after 2 months, comparable to the thermal treated ones. Among the tested treatments, 400 MPa may be considered as the best option for the quality retention during storage.

Effects of Multihollow Surface Dielectric Barrier Discharge Plasma on Chemical and Antioxidant Properties of Peanut

An experiment was conducted to investigate the effects of atmospheric pressure plasma generated by multihollow surface dielectric barrier discharge on chemical and antioxidant properties of peanut. Multihollow surface dielectric barrier discharge is a novel plasma device applicable in food industry applications due to the capacity of the generated plasma to treat the surface of food without changing the quality. Peanut seeds were exposed to the multihollow plasma for different plasma power (10–40 W), air flow rate (0.5–20 l/min), and time (1–15 min). The fatty acid profile, peroxide value, acid value, moisture content, total polyphenols, and antioxidant activity were evaluated during cold plasma treatment. The result revealed that, due to the variation plasma power, treatment time and air flow rate caused a decrease in unsaturated fatty acid and moisture content and increased saturated fatty acids, peroxide value, acid value, and total polyphenols of the peanut.

Opinion on the Hurdles and Potential Health Benefits in Value-Added Use of Plant Food Processing By-Products as Sources of Phenolic Compounds

Plant foods, their products and processing by-products are well recognized as important sources of phenolic compounds. Recent studies in this field have demonstrated that food processing by-products are often richer sources of bioactive compounds as compared with their original feedstock. However, their final application as a source of nutraceuticals and bioactives requires addressing certain hurdles and challenges. This review discusses recent knowledge advances in the use of plant food processing by-products as sources of phenolic compounds with special attention to the role of genetics on the distribution and biosynthesis of plant phenolics, as well as their profiling and screening, potential health benefits, and safety issues. The potentialities in health improvement from food phenolics in animal models and in humans is well substantiated, however, considering the emerging market of plant food by-products as potential sources of phenolic bioactives, more research in humans is deemed necessary.

Ultrasound-Induced Escherichia coli O157:H7 Cell Death Exhibits Physical Disruption and Biochemical Apoptosis

Ultrasound has attracted great interest of both industry and scientific communities for its potential use as a physical processing and preservation tool. In this study, Escherichia coli O157:H7 was selected as the model microbe to investigate the ultrasound-induced cell death. Slight variations in membrane potential and ion exchanges across membrane induced by low-intensity ultrasound increased the membrane permeability of E. coli O157:H7, and this reversible sublethal effect can preserve the viability of E. coli O157:H7 and meanwhile be beneficial for bioprocessing application. In comparison, high-intensity ultrasound resulted in irreversible lethal effect on E. coli O157:H7, which can be applied in the field of microbial inactivation. In addition, both low- and high-intensity ultrasound induced either physical destruction or trigger genetically encoded apoptosis of E. coli O157:H7. Accumulation of reactive oxygen species and decrease of adenosine tri-phosphate might be related to the physiological and biochemical hallmarks of apoptosis, including exposed phosphatidylserine and activated caspases in E. coli O157:H7. The result provides novel insight into the mechanisms of non-thermal physical treatment on the inactivation of bacteria and lays foundation for the further research on the cell signaling and metabolic pathway in apoptotic bacteria.

Effects of Instant Controlled Pressure Drop (DIC) Drying on the Texture and Tissue Morphology of Fruits and Vegetables

The effects of instant controlled pressure drop (DIC) drying, and blanching-assisted DIC (B + DIC) on texture, volume ratio (VR), colour, microstructures of different tissues, and cell-morphology of fruit and vegetable chips was examined. Results revealed that B + DIC had a significant effect on fruits and vegetable chips as compared with DIC treated. The DIC dried mango chips were observed to have low hardness (26.12 N) and maximum crispness (10.43) that were also observed in mango chips under B + DIC treated (14.66), exhibiting a puffy structure and crispy texture. Well expanded structure which reflected by VR was found in the mango (0.46 mL) and king oyster mushroom (KOM) (0.36 mL) chips under both treatments. The maximum total colour changes (∆E) were also obtained in the mango (30.40) and carrot (42.87) chips under B + DIC. The microstructures of the apple, carrot, KOM and potato chips products, which corresponded to its well expanded appearances, showed a honeycomb-like pores structure, observed for DIC treated apple, fresh potato, B + DIC dried KOM as well as in sweet potato. In addition, the B + DIC-treated carrot chips, pores size, increased the cell wall and expanded. Moreover, the mushroom chips mostly were shrunken after hot water blanching.

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.

Three Pillars of Novel Nonthermal Food Technologies: Food Safety, Quality, and Environment

This review gives an overview of the impact of novel nonthermal food technologies on food safety, on quality, and on the environment. It confirms that research in this field is mainly focused on analyzing microbial and/or chemical aspects of food safety. However, recent research shows that in spite of various food safety benefits, some negative (quality oriented) features occur. Finally, this paper shows the necessity of analyzing the environmental dimension of using these technologies.

Chemical Modifications of Lipids and Proteins by Nonthermal Food Processing Technologies

A range of nonthermal techniques have demonstrated process efficacy in ensuring product safety, extension of shelf life, and in general a retention of key quality attributes. However, various physical, chemical and biochemical effects of nonthermal techniques on macro and micro nutrients are evident, leading to both desirable and undesirable changes in food products. The objective of this review is to outline the effects of nonthermal techniques on food chemistry and the associated degradation mechanisms with the treatment of foods. Oxidation is one of the key mechanisms responsible for undesirable effects induced by nonthermal techniques. Degradation of key macromolecules largely depends on the processing conditions employed. Various extrinsic and intrinsic control parameters of high-pressure processing, pulsed electric field, ultrasound processing, and cold atmospheric plasma on chemistry of processed food are outlined. Proposed mechanisms and associated degradation of macromolecules, i.e., proteins, lipids, and bioactive molecules resulting in food quality changes are also discussed.

Frequency of Enteroparasites and Bacteria in the Leafy Vegetables Sold in Brazilian Public Wholesale Markets

The consumption of raw vegetables is related to health benefits. However, these foods might be source of foodborne diseases. The objective of the present study was to perform a microbiological and parasitological evaluation of the leafy vegetables commercially sold in five regions of Brazil at public wholesale markets. The 12 types of leafy vegetables (144 samples) were curly lettuce, looseleaf lettuce, red lettuce, chives, coriander, kale, basil, arugula, parsley, iceberg lettuce, chicory, and bean sprouts. The prevalences of total coliforms (88 to 100%) and thermotolerant coliforms (37 to 100%) were high, but Salmonella was not detected in any of the analyzed samples. All open markets sold vegetables contaminated with enteroparasites, mainly Entamoeba sp., Balantidium coli, Strongyloides sp., Ascaris sp., Enterobius vermicularis, and Ancylostomidae. Contamination was detected in all the regions (north, northeast, central west, southeast, and south) and types of vegetables, with higher prevalences in the northeast region, mainly in basil, lettuce, and chives. Contamination of vegetables by potentially pathogenic microorganisms is a national problem, and the distribution centers should improve quality control of these commercial vegetables. Considering the high frequency of enteroparasites and bacteria and the potential risk of disease transmitted by vegetables, we suggest greater enforcement of the sanitary surveillance of food offered to the public.

Effects of dielectric barrier discharge plasma on the inactivation of Zygosaccharomyces rouxii and quality of apple juice

This work aimed to evaluate the effects of dielectric barrier discharge (DBD) plasma on inactivation of spoilage yeast Zygosaccharomyces rouxii (Z. rouxii), in apple juice. Results showed that DBD plasma treatment at 90 W for 140 s resulted in about 5-log reduction of Z. rouxii in apple juice. The levels of extracellular nucleic acids and proteins as well as contents of H₂O₂ and NO₂^- in yeast extract-peptone-dextrose (YPD) medium increased significantly after DBD plasma treatment at 90 W for 40-200 s. The increases in membrane permeability and generation of reactive species would likely contribute to DBD plasma-mediated inactivation of Z. rouxii. DBD plasma caused significant changes in pH, titratable acidity, and certain color parameters of apple juice, but had no effect on the contents of total soluble solids, reducing sugar, and total phenolics. This study provides key implications for the application of DBD plasma in fruit juice processing.

Cold atmospheric plasma manipulation of proteins in food systems

Plasma processing has been getting a lot of attention in recent applications as a novel, eco-friendly, and highly efficient approach. Cold plasma has mostly been used to reduce microbial counts in foodstuff and biological materials, as well as in different levels of packaging, particularly in cases where there is thermal sensitivity. As it is a very recent application, the impact of cold plasma treatment has been studied on the protein structures of food and pharmaceutical systems, as well as in the packaging industry. Proteins, as a food constituent, play a remarkable role in the techno-functional characteristics of processed foods and/or the physico-chemical properties of protein-based films. At the same time, some proteins are responsible for reduction in quality and nutritional value, and/or causing allergic reactions in the human body. This study is a review of the influences of different types of plasma on the conformation and function of proteins with food origin, especially enzymes and allergens, as well as protein-made packaging films. In enzyme manipulation with plasma, deactivation has been reported to be either partial or complete. In addition, an activity increase has been observed in some cases. These variations are caused by the effect of different active species of plasma on the enzyme structure and its function. The level and type of variations in the functional properties of food proteins, purified proteins in food, and plasma-treated protein films are affected by a number of control factors, including treatment power, time, and gas type, as well as the nature of the substance and the treatment environment.

A review on microbiological decontamination of fresh produce with nonthermal plasma

Food safety is a critical public health issue for consumers and the food industry because microbiological contamination of food causes considerable social and economic burdens on health care. Most foodborne illness comes from animal production, but as of the mid-1990s in the United States and more recently in the European Union, the contribution of fresh produce to foodborne outbreaks has rapidly increased. Recent studies have suggested that sterilization with nonthermal plasma could be a viable alternative to the traditional methods for the decontamination of heat-sensitive materials or food because this technique proves capable of eliminating micro-organisms on surfaces without altering the substrate. In the last 10 years, researchers have used nonthermal plasma in a variety of food inoculated with many bacterial species. All of these experiments were conducted exclusively in a laboratory and, to our knowledge, this technique has not been used in an industrial setting. Thus, the purpose of this review is to understand whether this technology could be used at the industrial level. The latest researches using nonthermal plasma on fresh produce were analysed. These evaluations have focused on the log reduction of micro-organisms and the treatment time.

Bacteriocins from lactic acid bacteria and their potential in the preservation of fruit products

Bacteriocins produced by lactic acid bacteria (LAB) are well-recognized for their potential as natural food preservatives. These antimicrobial peptides usually do not change the sensorial properties of food products and can be used in combination with traditional preservation methods to ensure microbial stability. In recent years, fruit products are increasingly being associated with food-borne pathogens and spoilage microorganisms, and bacteriocins are important candidates to preserve these products. Bacteriocins have been extensively studied to preserve foods of animal origin. However, little information is available for their use in vegetable products, especially in minimally processed ready-to-eat fruits. Although, many bacteriocins possess useful characteristics that can be used to preserve fruit products, to date, only nisin, enterocin AS-48, bovicin HC5, enterocin 416K1, pediocin and bificin C6165 have been tested for their activity against spoilage and pathogenic microorganisms in these products. Among these, only nisin and pediocin are approved to be commercially used as food additives, and their use in fruit products is still limited to certain countries. Considering the increasing demand for fresh-tasting fruit products and concern for public safety, the study of other bacteriocins with biochemical characteristics that make them candidates for the preservation of these products are of great interest. Efforts for their approval as food additives are also important. In this review, we discuss why the study of bacteriocins as an alternative method to preserve fruit products is important; we detail the biotechnological approaches for the use of bacteriocins in fruit products; and describe some bacteriocins that have been tested and have potential to be tested for the preservation of fruit products.

Ellagitannin-rich bioactive extracts of Tuberaria lignosa: insights into the radiation-induced effects in the recovery of high added-value compounds

Functional extracts with the highest concentration of ellagitannins were obtained from samples irradiated at 5 kGy, extracted for 10 min.

Modified atmosphere packaging and post-packaging irradiation of Rumex induratus leaves: a comparative study of postharvest quality changes

The effects of conventional and inert-gas enriched atmospheres, as well as those caused by different γ-irradiation doses, on buckler sorrel (Rumex induratus) leaves quality were evaluated and compared after 12 days of storage at 4 °C. The green colour of the abaxial surface of the leaves was relatively stable, as well as the carbohydrates content and the calorific value. The storage time decreased the amounts of fructose, glucose, trehalose, α-tocopherol, and β-tocopherol and increased the levels of total organic acids and δ-tocopherol. The total tocopherols content was higher in air-packaged non-irradiated leaves, antioxidant compounds that may have contributed to the preservation of polyunsaturated fatty acids (PUFA). Some antioxidant properties were also favoured during storage. It was found that the overall postharvest quality of buckler sorrel leaves is better maintained with the argon-enriched atmospheres, while the 6 kGy dose was a suitable option to preserve PUF+A during cold storage. This study highlights the suitability of the applied postharvest treatments and the interest to include buckler sorrel leaves in contemporary diets.