Effect of pulsed light treatments on quality and antioxidant properties of fresh-cut strawberries

Microwave-assisted hydrodiffusion and gravity extraction: An efficient method to produce pomegranate juice

Green technologies based on microwaves have been developed by the food industry to produce organoleptically acceptable fruit juices without preliminary processing. Microwave irradiation coupled with hydrodiffusion and gravity (MHG) combines microwave heating with the earth's gravity, allowing the collection of hydrophilic substances released from the irradiated matrix. To the best of our knowledge, MHG extraction has never been experimented to produce pomegranate juice. In this work, we have evaluated it as a potential alternative to the conventional squeezing. A central composite design study (CCD) allowed the selection of the best extractive conditions (irradiation power and extraction time) to obtain a pomegranate juice with higher yield, polyphenol (e.g., catechin and delphinidin-3,5-glucoside) content, and related bioactivities (antioxidant and antidiabetic) than the one obtained by squeezing while maintaining the chemical-physical properties. Thus, this technique appears to be a functional alternative to producing high value pomegranate juice.

Pulsed light treatment of whole white button mushroom (Agaricus bisporus): Kinetics and mechanism of microbial inactivation and storage study

The whole white button mushrooms (WWBMs) are highly perishable due to susceptibility to microbial spoilage. This study explored the potential of pulsed light (PL) treatment for decontamination and shelf-life extension of WWBM. WWBM surface was inoculated with Escherichia coli, Listeria monocytogenes, and Aspergillus niger spores (8.1, 8.0, and 8.05 log10 CFU/g, respectively) and tested for inactivation against various PL intensities (fluence 0.13-0.75 J/cm2). The kinetics and mechanism of microbial inactivation were explored, and shelf life was determined at 4, 20, and 37°C. Microbial inactivation increased with increasing PL intensity. PL-induced microbial inactivation was well explained by Weibull model with shape parameters (β-value) for E. coli, L. monocytogenes, A. niger, aerobic mesophiles, and yeast and mold as 0.87, 0.92, 0.91, 0.89, and 0.94, respectively. PL-treatment at 0.75 J/cm2 resulted in >5-log cycle reduction in all inoculated and natural microorganisms. Exposure to PL led to collapse of cellular structure, ruptured cell wall, and leakage of cellular material in all microorganisms and spores along with alterations in nucleic acid and lipid bands. At 4°C, maximum shelf life of 5 days was achieved when WWBM was exposed at 0.75 J/cm2. The WWBM retained 83.3% phenolics, 83.9% antioxidant capacity, and 77.4% vitamin D2 at 4°C while reducing the polyphenol oxidase and peroxidase activity by 89% and 79%. The degradation rate for quality parameters increased with storage temperature. The activation energy of the browning index affirmed it as the most sensitive quality attribute during storage. The study concluded the potential of PL treatment to prolong the shelf life of WWBM.

Radical species generating technologies for decontamination of Listeria species in food: a recent review report

Foodborne illnesses occur due to the contamination of fresh, frozen, or processed food products by some pathogens. Among several pathogens responsible for the illnesses, Listeria monocytogenes is one of the lethal bacteria that endangers public health. Several preexisting and novel technologies, especially non-thermal technologies are being studied for their antimicrobial effects, particularly toward L. monocytogenes. Some noteworthy emerging technologies include ultraviolet (UV) or light-emitting diode (LED), pulsed light, cold plasma, and ozonation. These technologies are gaining popularity since no heat is employed and undesirable deterioration of food quality, especially texture, and taste is devoided. This review aims to summarize the most recent advances in non-thermal processing technologies and their effect on inactivating L. monocytogenes in food products and on sanitizing packaging materials. These technologies use varying mechanisms, such as photoinactivation, photosensitization, disruption of bacterial membrane and cytoplasm, etc. This review can help food processing industries select the appropriate processing techniques for optimal benefits, in which the structural integrity of food can be preserved while simultaneously destroying L. monocytogenes present in foods. To eliminate Listeria spp., different technologies possess varying mechanisms such as rupturing the cell wall, formation of pyrimidine dimers in the DNA through photochemical effect, excitation of endogenous porphyrins by photosensitizers, generating reactive species, causing leakage of cellular contents and oxidizing proteins and lipids. These technologies provide an alternative to heat-based sterilization technologies and further development is still required to minimize the drawbacks associated with some technologies.

Phytochemical Investigation of Sumac (Rhus coriaria L.) Fruits from Different Sicilian Accessions

Sumac, Rhus coriaria L., is employed as a natural preservative in the food sector, due to its rich content of antioxidant compounds, including hydrolysable tannins, phenolic acids, anthocyanins, and flavonoids. In this work, the phytochemical characterization of sumac fruits from five Sicilian accessions was performed to evaluate their potential as a food preservative for nutraceutical exploitation. Spectrophotometric tests and HPLC-MS/MS analyses were conducted to assess and compare the antioxidant power of the water extracts produced with the five sumac accessions. Principal component analysis was also carried out to better visualize the obtained results. Flavonoids and phenolic acids, namely isoquercitrin (20,342.82 mg/kg dry extract) and gallic acid (197,489.19 mg/kg dry extract), were more abundant in fruits from the population of San Biagio Platani, while the one from Giarratana was characterized by a higher content of anthocyanins such as cyanidin-3-glucoside (20,889.81 mg/kg dry extract). These two populations can be recognized as the most suitable settings for the implementation of sumac cultivation and the development of sumac-based products, especially for food and nutraceutical purposes.

Non-thermal technologies for the conservation of açai pulp and derived products: A comprehensive review

Açai (Euterpe oleracea) is one of the main sustainable extractive crops in the Amazon region, widely consumed by the local population and a significant export product. This review presents the current knowledge regarding nonthermal technologies employed in açai processing. This review aims to discuss and compare the main results attained by the application of HPP, ultrasound, ozone, UV light, cold plasma, and pulsed electric field on microbial inactivation, enzymatic inhibition, and the content of anthocyanin and other bioactive compounds after açai pulp processing. The discussion compares these technologies with pasteurization, the current main technology applied to açai sanitization. This review shows that there are still many gaps to be filled concerning açai processing in thermal and non-thermal technologies. Data analysis allowed the conclusion that pasteurization and HPP are, up to now, the only technologies that enable a 5-log CFU reduction of yeasts, molds, and some bacteria in açai. However, no study has reported the inactivation of Trypanosoma cruzi, which is the major gap found in current knowledge. Other technologies, such as pulsed electric field, cold plasma, and ultrasound, require further development and process intensification studies to be as successful as HPP and pasteurization.

Effect of pulsed light on myofibrillar protein of large yellow croaker (Pseudosciaena crocea) during refrigerated storage

This study mainly evaluated the effect of different energies of pulsed light (PL) treatment (100, 200, 300, 400, and 500 J/pulse) on myofibrillar protein (MP) of large yellow croaker during refrigerated storage. The results showed that PL treatment would cause a certain degree of oxidation to the MP of large yellow croaker at the initial stage, which showed that the total sulfhydryl content of the protein decreased, the carbonyl content and the average particle size increased, and the β-sheet to β-turn transformation, the tertiary structure of the protein unfolds, and the hydrophobic groups were exposed, causing the reduction of intrinsic fluorescence intensity. However, subsequent storage studies found that PL treatment could slow down the oxidation rate of MP. The decrease rate of total sulfhydryl content and the increase rate of carbonyl content in the 300 J/pulse group were both reduced by about 1.7 times compared with the control group. At the same time, the PL treatment with this intensity could also better protect the secondary structure, tertiary structure, and microstructure of MP. This study provided theoretical basis and reference for analyzing the quality change rule and mechanism of large yellow croaker during refrigerated storage after PL treatment. Studies have shown that PL treatment can reduce the adverse changes of MP in large yellow croaker during cold storage.

Effect of pulsed light on curcumin chemical stability and antioxidant capacity

Curcumin is the major bioactive component in turmeric with potent antioxidant activity. Little is known about how pulsed light (PL) technology (an emerging non-thermal food processing technology relying on high intensity short duration flashes of light) can affect the chemical stability and antioxidant capacity of curcumin. This study found that PL treatment of fluence levels from 0 to 12.75 J/cm2 produced a fluence-dependent reduction in curcumin content. These results paralleled the production of a tentative curcumin dimer, identified as a potential photochemical transformation product. PL-treated curcumin at relatively higher fluence levels decreased chemical-based ORAC and ABTS antioxidant capacity, relative to control (P < 0.05). This contrasted the effect observed to increase coincidently both intracellular antioxidant capacity (e.g., DCFH-DA (P < 0.05)) and GSH/GSSG ratio (P < 0.05), respectively, in cultured differentiated Caco-2 cells. In conclusion, the application of PL on curcumin results in photochemical transformation reactions, such as dimerization, which in turn, can enhance biological antioxidant capacity in differentiated Caco-2 cells.

Microwave Hydrodiffusion and Gravity Extraction of Vitamin C and Antioxidant Compounds from Rosehips (Rosa canina L.)

Rosehips, Rosa canina L. (Rosaceae family), have been used for a long time for their beneficial effects on health, and they are largely exploited in the food and nutraceutical supplement sectors. The aim of this work was to apply and optimize for the first time the microwave hydrodiffusion and gravity (MHG) extraction of rosehips, as a novel application of solvent-free microwave extraction, previously conducted in a similar way only on mulberry, strawberry, and onion. The optimization was performed through a central composite design (CCD) by evaluating the effect of the experimental parameters on the yield; total polyphenol, flavonoid, and anthocyanin contents; radical scavenging activity; and content of vitamin C in the obtained extracts. As a result, the water moistening pretreatment was clearly revealed to possess a pivotal role in the quality of the rosehip extracts. Among the evaluated responses, the yield, the anthocyanin content, and the antioxidant activity were well described by the statistical model. Notably, the optimized MHG extract was compared with the ones obtained by conventional solvent extraction showing higher amounts of vitamin C, polyphenols, flavonoids, and anthocyanins, while the traditional extracts performed better in terms of yield. In conclusion, MHG represents a promising alternative to standard extraction methods for obtaining rosehip extracts rich in vitamin C and antioxidant compounds. In this respect, the results of our research support the employment of MHG on an industrial level for the production of rosehip-based food supplements enriched in vitamin C.

Phototreatment (below 1100 nm) improving quality attributes of fresh-cut fruits and vegetables: A review

The emerging area of phototreatment technology has shown a significant potential to enhance the quality of fresh-cut fruit and vegetable products (FFVP). This review critically evaluates relevant literatures to address the potential for phototreatment technology (Red, blue, green, ultraviolet and pulsed light) applied to FFVP, outline the key to the success of phototreatment processing, and discuss the corresponding problems for phototreatment processing along with research and development needs. Base on photothermal, photophysical and photochemical process, phototreatment displays a great potential to maintain quality attributes of FFVP. The operating parameters of light, the surface properties and matrix components of the targeted material and the equipment design affect the quality of the fresh-cut products. To adapt current phototreatment technology to industrial FFVP processing, it is necessary to offset some limitations, especially control of harmful substances (For example, nitrite and furan) produced by phototreatment, comparison between different phototreatment technologies, and establishment of mathematical models/databases.

Optimization of Solvent-Free Microwave-Assisted Hydrodiffusion and Gravity Extraction of Morus nigra L. Fruits Maximizing Polyphenols, Sugar Content, and Biological Activities Using Central Composite Design

Black mulberry, Morus nigra L. (family: Moraceae), is a healthy food and medicinal plant. Microwave hydrodiffusion and gravity (MHG) is one of the most innovative applications of solvent-free microwave extraction. The aim of this study was to optimize for the first time the MHG solvent-free extraction of polyphenols and sugars from M. nigra fruits. Optimization was carried out using a central composite design (CCD) with selected responses such as extraction yield, total polyphenol (TPC), flavonoid (TFC), anthocyanin (TAC), and sugar (TSC) contents, in addition to DPPH radical scavenging, and α-glucosidase (AGHi), lipase (Li), and xanthine oxidase (XOi) inhibition as tools to evaluate the best parameters for efficient and rapid extraction of black mulberry. The optimized extract was characterized in terms of the aforementioned parameters to validate the models, and was further analyzed for 36 individual polyphenols using HPLC-MS/MS. The optimized MHG extract was finally compared with traditional extracts, and demonstrated much better performance in terms of TPC, TAC, and Li, while the traditional extracts showed better XOi and AGHi. In conclusion, MHG is a valuable green technique for the production of non-degraded black mulberry polyphenol-rich extract and we suggest its larger use in the pharmaceutical and food industries.

Effects of konjac glucomannan/pomegranate peel extract composite coating on the quality and nutritional properties of fresh-cut kiwifruit and green bell pepper

The effects of an edible coating, based on konjac glucomannan (KG) incorporated with pomegranate peel extracts (PE), on the physicochemical and nutritional properties of fresh-cut kiwifruit and green bell pepper during storage were investigated. The optimal extract time (40.6 min), temperature (54.5 °C), and ultrasound power (255.5 W) with response surface method, provided a high total antioxidant activity (TAA) of (92.31 ± 1.43)%. Fresh-cut kiwifruit and green bell pepper were coated by dipping using five treatments (distilled water, ascorbic acid, KG, PE, KG + PE), packed into polymeric film and stored for 8 days at 10 °C. Distilled water treatment was used as control. KG + PE treatment resulted in the highest total soluble solid and titratable acidity in fresh-cut kiwifruit, while the maximum firmness in fresh-cut green bell pepper. The weight loss was both effectively decreased in samples treated with KG or KG + PE. All samples treated with KG + PE had significantly higher contents of chlorophyll, ascorbic acid, total phenolic and TAA than others. Moreover, the KG + PE group had the lowest counts of microorganisms in all samples. KG coating incorporated with PE was proved to be efficient in maintaining the physico-chemical and nutritional properties of fresh-cut kiwifruit and green bell pepper during low temperature storage compared with control.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05006-7.

Application of pulsed light technology for fruits and vegetables disinfection: A review

Non-thermal technologies can maintain fruit and vegetable products quality better than traditional thermal processing. Pulsed light (PL) is a non-thermal method for microbial inactivation (vegetative cells and spores) in fruits and vegetables. The PL treatment involves the application of intense and short-duration pulses of broad spectrum wavelengths ranging from UV to near-infrared (100-1100 nm). This review summarized application of PL technology to control microbial contamination and increasing shelf-life of some fruits and vegetables including apple, blueberries, grape, orange, strawberries, carrot, lettuce, spinach, and tomato. The microbial inactivation in very short treatment times, low energy used by this system, flexibility for solid or liquid samples, few residual compounds and no synthetic chemicals that cause environmental pollution or harm humans, is benefits of PL technique. The efficiency of PL disinfection is closely associated with the input voltage, fluence (energy dose), composition of the emitted light spectrum, number of lamps, the distance between samples and light source, and frequency and number of applied pulses. The PL treatments control pathogenic and spoilage microorganisms, so it facilitates the growth and development of the starter microorganisms affecting product quality.

Emerging Non-Thermal Technologies for the Extraction of Grape Anthocyanins

Anthocyanins are flavonoid pigments broadly distributed in plants with great potential to be used as food colorants due to their range of colors, innocuous nature, and positive impact on human health. However, these molecules are unstable and affected by pH changes, oxidation and high temperatures, making it very important to extract them using gentle non-thermal technologies. The use of emerging non-thermal techniques such as High Hydrostatic Pressure (HHP), Ultra High Pressure Homogenization (UHPH), Pulsed Electric Fields (PEFs), Ultrasound (US), irradiation, and Pulsed Light (PL) is currently increasing for many applications in food technology. This article reviews their application, features, advantages and drawbacks in the extraction of anthocyanins from grapes. It shows how extraction can be significantly increased with many of these techniques, while decreasing extraction times and maintaining antioxidant capacity.

Intensive pulsed light pretreatment combined with controlled temperature and humidity for convection drying to reduce browning and improve quality of dried shiitake mushrooms

BACKGROUND

The change of surface color caused by browning during the drying process of shiitake mushrooms seriously affects its market circulation. Intensive pulsed light (IPL) as a non-heat-treatment method can reduce enzyme activity by changing the enzyme structure. Therefore, in this study, the use of IPL pretreatment before drying was aimed to reduce the adverse reactions caused by the browning reaction during the drying processing of shiitake mushrooms.

RESULTS

Shiitake mushrooms pretreated with 25 pulses of IPL energy of 400 J reduced the initial polyphenol oxidase enzyme activity, the browning index, and browning degree values by 42.83%, 43.02%, and 47.54% respectively. The IPL pretreatment enhanced the polysaccharides and reducing sugars contents and it reduced 5-hydroxymethylfurfural generation in the dried shiitake mushrooms. The pretreatment also improved the surface color, the antioxidant activity, and retained the umami taste characteristics in the dried shiitake mushroom.

CONCLUSION

The IPL pretreatment combined with controlled temperature and humidity for convection drying could be a suitable method to improve the quality of dried shiitake mushrooms. Therefore, this study provides a new pretreatment method for materials that are prone to browning during drying. © 2021 Society of Chemical Industry.

Composite Films of Thermoplastic Starch and CaCl2 Extracted from Eggshells for Extending Food Shelf-Life

Calcium chloride (CaCl2) has been widely used to maintain the quality of fresh-cut fruits and vegetables because it stabilizes and strengthens the membrane system against fungal attacks. It is mainly applied via spray coating and dip coating techniques. This study explored a method of incorporating calcium chloride extracted from eggshells in a packaging material, thermoplastic starch (TPS), via a hot-melt extrusion process. The composites were characterized by FTIR, DSC, SEM-EDX and tensile testing. FTIR confirmed the chemical reactions between CaCl2 and TPS. DSC results showed a significant decrease in the heat of fusion by adding 20 wt% of CaCl2 content in TPS, indicating a drop in the degree of crystallinity. The Young’s modulus of TPS was not significantly affected by the incorporation of 10 wt% CaCl2 (P = 0.968), but reduced notably with the addition of 20 wt% CaCl2 (P = 0.05), indicating the plasticizer effect of the CaCl2. Physiochemical analysis of fresh-cut apple slices was assessed. Samples placed on the surface of the TPS/CaCl2 composites displayed less pH reduction, reduced antioxidant activity, more weight loss and increased reducing sugar compared to the samples placed on the surface of virgin TPS films. CaCl2 released from the TPS/CaCl2 films was measured and their antimicrobial activity was confirmed by bacterial inhibitory growth assessment. Fungal growth was observed on apple slices placed on virgin TPS film by day 21 while apple slices placed on TPS/CaCl2 20 wt% composites did not support any fungal growth for 28 days. In summary, TPS and eggshell-extracted CaCl2 showed the ability to maintain the quality of fresh-cut apples, and TPS/CaCl2 10 wt% composite could be a good option as a packaging material for fresh-cut fruits due to active antimicrobial activity and maintained Young’s modulus.

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.

Improvement of Must Fermentation from Late Harvest cv. Tempranillo Grapes Treated with Pulsed Light

Pulsed light irradiation is a nonthermal technology currently used for the elimination of pathogens from a diverse range of food products. In the last two decades, the results obtained using PL at laboratory scale are encouraging wine experts to use it in the winemaking industry. PL can reduce native yeast counts significantly, which facilitates the use of starter cultures, reducing SO2 requirements at the same time. In this experimental set up, Tempranillo grapes were subjected to pulsed light treatment, and the fermentative performance of non-Saccharomyces yeasts belonging to the species Schizosaccharomyces pombe, Lachancea thermotolerans, Torulaspora delbrueckii, Metschnikowia pulcherrima and Hanseniaspora vineae was monitored in sequential fermentations against spontaneous fermentation and pure culture fermentation with the species Saccharomyces cerevisiae. The experimental analyses comprised the determination of anthocyanin (High performance liquid chromatography with photodiode array detector-HPLC-DAD), polyphenol index and colour (Ultraviolet-visible spectroscopy-UV-Vis spectrophotometer), fermentation-derived volatiles (Gas chromatography with flame ionization detector-GC-FID), oenological parameters (Fourier transform Infrared spectroscopy-FT-IR) and structural damage of the skin (atomic force microscopy-AFM). The results showed a decrease of 1.2 log CFU/mL yeast counts after pulsed light treatment and more rapid and controlled fermentation kinetics in musts from treated grapes than in untreated samples. The fermentations done with treated grapes allowed starter cultures to better implant in the must, although a larger anthocyanin loss (up to 93%) and an increase in hue values (1 unit) towards more yellow hues were observed for treated grapes. The development of biomass was larger in musts from treated grapes. The profile of volatile compounds and oenological parameters reveals that fermentations carried out with untreated grapes are prone to deviations from native microbiota (e.g., production of lactic acid). Finally, no severe damage on the skin was observed with the AFM on treated grapes.

Improvement in storage quality of postharvest tomato fruits by nitroxyl liposomes treatment

Nitroxyl (HNO) has attracted much attention due to its unique biological activity. To investigate the preservation effect of HNO on fruits, a nitroxyl liposome based on 1-nitrosocyclohexyl acetate was prepared and characterized by infrared spectroscopy and transmission electron microscopy. The optimal preparation conditions were explored, and then HNO liposomes were prepared under the optimal conditions to study the effect of HNO liposomes on postharvest quality of tomatoes. The tomato fruits were treated with different concentrations (0, 5, 10, 15 and 20 μmol L^-1) of HNO liposomes and stored at room temperature. The results indicated that treatment with HNO liposomes can more effectively delay the browning and slow down the decrease in lightness of tomatoes. Additionally, HNO liposomes can reduce the activity of PPO and POD, inhibit the increase of MDA and total phenol content. These results suggest that treatment with HNO liposomes can effectively preserve the quality of tomatoes.

Effect of light on sensory quality, health-promoting phytochemicals and antioxidant capacity in post-harvest baby mustard

The effect of light exposure on sensory quality, health-promoting phytochemical contents, and antioxidant capacity in the lateral buds of baby mustard plants was investigated at ambient storage temperature (20 °C). The results showed that light exposure (36 μmol m^-2 s^-1) during post-harvest storage significantly prolonged shelf life (more than 1.75-fold), delayed the weight loss and the decrease of firmness. Light treatments also enhanced chlorophyll and carotenoid contents, and retarded declines in contents of soluble sugars, ascorbic acid, flavonoids and glucosinolates, as well as antioxidant capacity. The quality of baby mustard plants receiving 24 h daily light treatment was superior to those in plants receiving 12 h treatment and constant darkness at 20 °C. These findings indicate that light exposure, especially 24 h treatment, is an effective method of prolonging shelf life and maintaining sensory and nutritional qualities in baby mustard plants stored at ambient temperature.

Application of citronella and rose hydrosols reduced enzymatic browning of fresh-cut taro

Hydrosols are byproducts produced by steam distillation of aromatic plant materials. Previous studies reported hydrosols owned effectively inhibitory effects on microbials, but few focused on the effects in reducing enzymatic browning of fresh-cut products. Here, application of citronella hydrosol (CH) and rose hydrosol (RH) obviously reduced values of L*, a* and b* in surfaces of fresh-cut taros, suggesting these hydrosols could reduce browning severity. About 500 ml/L of RH and CH reduced total phenol contents, and activities of phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), suggesting hydrosols suppressed browning development by reducing PAL, POD and PPO activities. Studies reported terpenoids had potential inhibition on PPO activity. Chemical composition analysis showed that RH and CH extracts contained abundant terpenoids. These imply that terpenoids contained in two hydrosols might have contributed to the reduction of enzyme activity. This study indicates that hydrosols might be promising natural anti-browning agents for fresh-cut foods. PRACTICAL APPLICATIONS: Hydrosols are the byproducts of essential oil from steam distillation. The work described here shows that application of citronella and rose hydrosols significantly reduced the browning of fresh-cut taros. Moreover, aromatic hydrosols also present inhibitory activity against microorganisms and are generally considered safe for human health. These suggested that aromatic hydrosols are the natural and useful anti-browning agents to preserve the quality of fresh cut foods, and can be well integrated into industrial procedures.

Developments and applications of nanomaterial-based carbon paste electrodes

This review summarizes the progress that has been made in the past ten years in the field of electrochemical sensing using nanomaterial-based carbon paste electrodes. Following an introduction into the field, a first large section covers sensors for biological species and pharmaceutical compounds (with subsections on sensors for antioxidants, catecholamines and amino acids). The next section covers sensors for environmental pollutants (with subsections on sensors for pesticides and heavy metal ions). Several tables are presented that give an overview on the wealth of methods (differential pulse voltammetry, square wave voltammetry, amperometry, etc.) and different nanomaterials available. A concluding section summarizes the status, addresses future challenges, and gives an outlook on potential trends.

Postharvest application of pectic-oligosaccharides on quality attributes, activities of defense-related enzymes, and anthocyanin accumulation in strawberry

BACKGROUND

The postharvest application of pectic-oligosaccharides (POS) as an elicitor to improve the postharvest shelf-life and nutritional quality by stimulating natural defense mechanisms in strawberries was studied. Strawberries (cv. Festival) were treated with POS (at 0, 2, 5, and 9 g L^-1 ) and evaluated for firmness, weight loss, color, soluble solids, titratable acidity (TA), total phenolic and anthocyanin content, antioxidant capacity, decay, and some defense-related enzyme activity during storage at 2 ± 0.5 °C for 14 days.

RESULTS

Treatment with POS significantly delayed (P < 0.05) strawberry decay, and reduced the water loss and softening of fruit during storage. Strawberries treated with POS showed a significant increase in total phenolic and anthocyanin content, and antioxidant capacity when compared with controls. Interestingly, POS induced higher activity of phenylalanine ammonia-lyase (PAL), chitinase, and β-1,3-glucanase in strawberries. Compared to the control, the activity of enzymes was markedly increased in fruit treated with all tested POS concentrations, particularly chitinase, and β-1,3-glucanase activities, but 5 and 9 g L^-1 POS were the most effective treatments for maintaining the quality attributes and improving anthocyanin accumulation and antioxidant capacity of strawberries.

CONCLUSION

These findings suggest that POS treatment could potentially be applied to maintain quality attributes, reduce decay, and further enrich the anthocyanin content and antioxidant capacity of strawberries during postharvest storage. The results also suggest that the positive effects of POS on strawberries could be associated with the rapid accumulation of chitinase and β-1,3-glucanase activities, and the increase of PAL enzyme activity leading to the synthesis and accumulation of anthocyanins. © 2019 Society of Chemical Industry.

Efficacy of pulsed-ultraviolet light for inactivation of Salmonella spp on black peppercorns

Efficacy of pulsed ultraviolet (PUV) to inactivate Salmonella pure culture and on inoculated black peppercorns was evaluated. Black peppercorns inoculated with Salmonella were subjected to PUV treatment (0.28 J/cm² /pulse) using two different sample holders, on a traditional flat surface or on a wave-shaped surface to increase surface exposure of peppercorns to PUV through light reflection. The temperature change on black peppercorns surface during treatment was recorded, and the effect of cooling period during PUV treatment was studied. PUV treatment of two pulses reduced Salmonella population by more than 6 log CFU/mL in phosphate-buffered saline. Continuous PUV treatment (80 pulses on each side) using a wave-shaped surface was able to reduce Salmonella by 1.9 log CFU/g; same treatment using flat surface reduced Salmonella by less than 1.5 log CFU/g. The temperature on peppercorns surface increased to 65 °C after 80 pulses continuous PUV treatment. Adding 280 s cooling time after every 20 pulses reduced the temperature from 65 to 40 °C and achieved similar Salmonella inactivation (P > 0.05) as the continuous PUV treatment. Results from this study showcase the effectiveness of PUV treatment for reducing Salmonella level on black peppercorns surface and provided insights on the potential implementation of PUV treatment at the industrial level. PRACTICAL APPLICATION: Results from this study showcased the effectiveness of PUV treatment for reducing Salmonella level on black peppercorns surface and provided insights on the potential implementation of PUV treatment at the industrial level.

Formation of patulin-glutathione conjugates induced by pulsed light: A tentative strategy for patulin degradation in apple juices

Patulin is a toxic mycotoxin usually associated with apple products. Due to its unhealthy effects for humans, its content is regulated by the food safety authorities. The removal or degradation of this mycotoxin in contaminated apple juices has been studied with different approaches with uneven effectiveness. However, a strategy based on the chemical reaction between patulin and glutathione (GSH), in order to generate the conjugates that are formed during cell detoxification process, is an innovative approach yet to be evaluated. In this work, the formation of patulin-GSH conjugates activated by the application of pulsed light treatments and catalyzed by Fe²⁺ ions was evaluated. The study of patulin degradation and effect of the GSH/Fe²⁺ molar ratio showed that a molar ratio of 5 allows an adequate catalytic effect of the metal ions. In addition, mono-substituted patulin-glutathione adducts were identified as the main type of generated conjugates.

Synergistic effects of ascorbic acid and plant-derived ceramide to enhance storability and boost antioxidant systems of postharvest strawberries

BACKGROUND

Excessive reactive oxygen species (ROS) may attack biological macromolecules and induce oxidative stress. The inhibition by ascorbic acid (AsA) on oxidative damage has been reported in fruits, while the barrier effect of ceramide has also been proven. However, there are few reports about the effects of ceramide-AsA interactions to enhance storability and boost antioxidant systems in fruits during storage. This study was conducted to study the synergistic effects of AsA in combination with ceramide on the quality of postharvest strawberry (Fragaria anannasa cv. Tianbao).

RESULTS

Treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide significantly delayed the rot of strawberries, reduced the water loss and the contents of ROS, malonaldehyde (MDA), and proline, however, increased the contents of total flavonoids, total phenols, and anthocyanins compared with other treatments. Also, treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide significantly increased the activities of peroxidase (POD) and superoxide dismutase (SOD) but inhibited the activity of polyphenol oxidase (PPO).

CONCLUSION

It is suggested that treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide could significantly reduce the oxidative damage and maintain the storage quality of strawberries during storage by enhancing the antioxidant systems. © 2019 Society of Chemical Industry.

Physiological and Metabolomic Analysis of Cold Plasma Treated Fresh-Cut Strawberries

Cold plasma technology offers new opportunities to the decontamination and preservation of fruits and vegetables. In the present research, strawberries were cut into four wedges and then treated with dielectric barrier discharge plasma at 45 kV for 1 min and stored for 1 week (4 °C). Metabolomic analysis suggested that plasma treatment improved the biosynthesis of the metabolites in the "flavones and flavonol biosynthesis" pathway and "biosynthesis of phenylpropanoids" pathway in fresh-cut strawberries. Physiological assay demonstrated that plasma treatment maintained the texture properties and inhibited microbial growth of fresh-cut strawberries. In addition, plasma treatment also promoted the accumulation of total phenolics, total flavonoid, and anthocyanin by enhancing the critical enzyme activities and activating related gene expression in phenylpropanoid as well as reactive oxygen species metabolism, which contributed greatly to the enhancement of antioxidant capacity of strawberry wedges. Our investigation provided a new perspective of the effect of plasma treatment on the safety and quality of strawberry wedges and suggested that cold plasma treatment holds promise as an emerging processing technology for improving the quality and antioxidant activity of postharvest fruits and vegetables.