Abstract The green-flesh (gf) mutant of the tomato fruit ripen to a muddy brown color and has been demonstrated previously to be a loss-of-function mutant. Here, we provide more evidence to support this view that SlSGR1 is involved in color change in ripening tomato fruits. Knocking out SlSGR1 expression using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 genome editing strategy showed obviously a muddy brown color with significantly higher chlorophyll and carotenoid content compared with wild-type (WT) fruits. To further verify the role of SlSGR1 in fruit color change, we performed transcriptome deep sequencing (RNA-seq) analysis, where a total of 354 differentially expressed genes (124/230 downregulated/upregulated) were identified between WT and slsgr1. Additionally, the expression of numerous genes associated with photosynthesis and chloroplast function changed significantly when SlSGR1 was knocked out. Taken together, these results indicate that SlSGR1 is involved in color change in ripening fruit via chlorophyll degradation and carotenoid biosynthesis.

Objectives The work intended to reveal the effect of cold shock (CS) treatment on chilling injury (CI), antioxidant capacity, and membrane fatty acid of peach fruit. Materials and methods Peaches were soaked in ice water (0 °C) for 10 min and stored at 5 °C for 28 days for determination, except CI, and then stored for 3 days at 20 °C, only CI was measured. The electrolyte leakage (EL) was measured by conductivity meter. The activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase) and key enzymes of membrane lipid metabolism (phospholipase D, lipase, and lipoxygenase) as well as reactive oxygen species (ROS; O2·– and H2O2) were measured with a spectrophotometer. An ELISA kit and gas chromatography were used to determine membrane lipids and membrane fatty acids. The relative gene expression was measured by real-time polymerase chain reaction analysis. Results The results showed that CS treatment effectively delayed CI, suppressed the increase of EL and malondialdehyde content. Meanwhile, CS-treated fruit exhibited lower level of ROS and higher activities of antioxidant enzymes. Furthermore, CS treatment inhibited the activities as well as the relative gene expression of key enzymes in membrane lipid metabolism. CS-treated fruits maintained higher membrane fatty acid unsaturation and lower phosphatidic acid content. Conclusions These results indicated that CS treatment effectively alleviated CI and maintained the integrity of cell membranes by inducing antioxidant-related enzyme activity and maintaining a higher ratio of unsaturated fatty acids to saturated fatty acids.

Background Acacia seyal gum (ASG) is an abundant source of natural polyphenolic compounds (NPPCs) and antioxidant activity with numerous benefits and is often used in cancer treatment. The type of extraction technique can significantly impact the yield and isolation of NPPCs from ASG. The traditional use of maceration extraction reportedly yields fewer NPPCs. Objectives This study investigated five extraction techniques for NPPCs and ASG antioxidant activity, namely: homogenisation, shaking, ultrasonication, magnetic stirring, and maceration. Materials and methods The evaluation of the antioxidant activity (AoA) of the extracted NPPCs from ASG used five assays, namely: total flavonoids content, Folin–Ciocalteu index, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric reducing antioxidant power, and cupric reducing antioxidant capacity. Results To minimise the data set dimensionality requires principal component analysis. The ultrasonic and maceration techniques were the best techniques to extract NPPCs and examine the AoA of ASG, with a high correlation between the NPPCs and AoA. However, the maceration process was slow (12 h) compared to ultrasonication (1 h). Slow extraction can result in a decline of the NPPCs due to polyphenol oxidase–enzyme and impact productivity. Conclusions These findings provide an essential guide for the choice of extraction techniques for the effective extraction of NPPCs from ASG and other plant materials.

Microbes on fresh apples are closely associated with fruit disease, preservation, and quality control. Investigation into the microbial communities on apples from different producing regions could reveal the microbial specificity and help disease prevention and quality control. In this paper, the apple surface microbes of 44 samples from two main Chinese apple-producing regions, Bohai Bay (BHB) and the Loess Plateau (LP), were investigated by sequencing fungal internal transcribed spacer and bacterial 16S rRNA hypervariable sequences. BHB and LP apples contained significantly different bacterial and fungal communities. BHB apples had a higher fungal diversity than LP apples. A total of 102 different fungal and bacterial taxonomies were obtained between apples from the two regions, in which 24 genera were predominant. BHB apples had higher phytopathogenic fungal genera, such as Tilletiopsis, Acremonium, Candida, and Phoma, indicating the higher phytopathogenic risks of apples from the humid climate of the BHB region. LP apples contained more bacterial genera identified as gut microbes, indicating the potential risks of contaminating apples with foodborne pathogens in the arid environment of the LP. This study highlighted the environment-oriented microbial specificity on apples from two main apple-producing regions, and provided a basis for further investigation.

A microelectrode glucose biosensor based on a three-dimensional hybrid nanoporous platinum/graphene oxide nanostructure was developed for rapid glucose detection of tomato and cucumber fruits. The nanostructure was fabricated by a two-step modification method on a microelectrode for loading a larger amount of glucose oxidase. The nanoporous structure was prepared on the surface of the platinum microelectrode by electrochemical etching, and then graphene oxide was deposited on the prepared nanoporous electrode by electrochemical deposition. The nanoporous platinum/graphene oxide nanostructure had the advantage of improving the effective surface area of the electrode and the loading quantity of glucose oxidase. As a result, the biosensor achieved a wide range of 0.1–20.0 mmol/L in glucose detection, which had the ability to accurately detect the glucose content. It was found that the three-dimensional hybrid nanostructure on the electrode surface realized the rapid direct electrochemistry of glucose oxidase. Therefore, the biosensor achieved high glucose detection sensitivity (11.64 μA·L/(mmol·cm2), low detection limit (13 μmol/L) and rapid response time (reaching 95% steady-state response within 3 s), when calibrating in glucose standard solution. In agricultural application, the as-prepared biosensor was employed to detect the glucose concentration of tomato and cucumber samples. The results showed that the relative deviation of this method was less than 5% when compared with that of high-performance liquid chromatography, implying high accuracy of the presented biosensor in glucose detection in plants.

Objectives Chilling injury is a prominent physiological disorder in longkong fruit pericarp when stored under 13 °C for a prolonged period. This study aimed to investigate the effects of individual salicylic acid (SA) and ultrasonication (US) treatments and of the combination salicylic acid and ultrasonication (SA-US) on alleviating the chilling injury symptoms in longkong fruit pericarp when in prolonged cold storage. Materials and methods SA (1 mmol/L) and US (40 kHz, 10 min at 90% amplitude, 350 W) were used as individual and combined (SA-US) treatments to control the chilling injury in longkong pericarp. The various quality measures were checked every 2 days in longkong for up to 18 days of cold storage (13 °C, 90% relative humidity). Results The results revealed that the control fruits treated with water exhibited severe chilling injury symptoms followed in rank order by US, SA, and SA-US cases. Treatments such as US and SA alone were more effective in controlling chilling injuries than control, while only minimal significant differences were noticed between them. On the other hand, the longkong pericarp treated with the SA-US combination had significantly increased antioxidant enzyme (superoxide dismutase and catalase) activities and decreased levels of membrane lytic (phospholipase D and lipoxygenase) enzymes and browning-inducing enzymes (phenylalanine ammonia lyase and polyphenol oxidase). Consequently, in the longkong pericarp, the chilling injury index, electrolytic leakage, respiration rate, weight loss, firmness, malondialdehyde content, changes in unsaturated and saturated fatty acid contents, and reactive oxygen species were significantly controlled by this treatment. Conclusions The present study concludes that longkong fruit treatment with a combination of US and SA is an excellent alternative for controlling the chilling injury symptoms and extending the shelf-life.

In the present study, the bactericidal efficacy of slightly acidic electrolyzed water (SAEW) against Listeria monocytogenes (L. monocytogenes) planktonic cells and biofilm on food-contact surfaces including stainless steel and glass was systematically evaluated. The results showed that SAEW (pH 5.09 and available chlorine concentration (ACC) of 60.33 mg/L) could kill L. monocytogenes on food-contact surfaces completely in 30 s, a disinfection efficacy equal to that of NaClO solutions (pH 9.23 and ACC of 253.53 mg/L). The results showed that long exposure time and high ACC contributed to the enhancement of the disinfection efficacy of SAEW on L. monocytogenes on food-contact surfaces. Moreover, the log reduction of SAEW treatment presented an increasing tendency within the prolonging of treatment time when SAEW was used to remove the L. monocytogenes biofilm formed on stainless steel and glass surfaces, which suggested that SAEW could remove L. monocytogenes biofilm effectively and its disinfection efficacy is equal to (in the case of stainless steel) or higher than (in the case of glass) that of high-ACC NaClO solutions. In addition, the results of the crystal violet staining and scanning electron microscopy also demonstrated that SAEW treatment could remove the L. monocytogenes biofilm on food-contact surfaces.

Dietary fiber (DF) is one of the major classes of nutrients for humans. It is widely distributed in the edible parts of natural plants, with the cell wall being the main DF-containing structure. DF content varies significantly in different plant species and organs, and the processing procedure can have a dramatic effect on the DF composition of plant-based foods. Given the considerable nutritional value of DF, a deeper understanding of DF in food plants, including its composition and biosynthesis, is fundamental to the establishment of a daily intake reference of DF and is also critical to molecular breeding programs for modifying DF content. In the past decades, plant cell wall biology has seen dramatic progress, and such knowledge is of great potential to be translated into DF-related food science research and may provide future research directions for improving the health benefits of food crops. In this review, to spark interdisciplinary discussions between food science researchers and plant cell wall biologists, we focus on a specific category of DF—cell wall carbohydrates. We first summarize the content and composition of carbohydrate DF in various plant-based foods, and then discuss the structure and biosynthesis mechanism of each carbohydrate DF category, in particular the respective biosynthetic enzymes. Health impacts of DF are highlighted, and finally, future directions of DF research are also briefly outlined.

In the present study, the bactericidal efficacy of slightly acidic electrolyzed water (SAEW) against Listeria monocytogenes (L. monocytogenes) planktonic cells and biofilm on food-contact surfaces including stainless steel and glass was systematically evaluated. The results showed that SAEW (pH 5.09 and available chlorine concentration (ACC) of 60.33 mg/L) could kill L. monocytogenes on food-contact surfaces completely in 30 s, a disinfection efficacy equal to that of NaClO solutions (pH 9.23 and ACC of 253.53 mg/L). The results showed that long exposure time and high ACC contributed to the enhancement of the disinfection efficacy of SAEW on L. monocytogenes on food-contact surfaces. Moreover, the log reduction of SAEW treatment presented an increasing tendency within the prolonging of treatment time when SAEW was used to remove the L. monocytogenes biofilm formed on stainless steel and glass surfaces, which suggested that SAEW could remove L. monocytogenes biofilm effectively and its disinfection efficacy is equal to (in the case of stainless steel) or higher than (in the case of glass) that of high-ACC NaClO solutions. In addition, the results of the crystal violet staining and scanning electron microscopy also demonstrated that SAEW treatment could remove the L. monocytogenes biofilm on food-contact surfaces.

Perchlorate concentrations in 387 unhusked rice samples from 15 main producing provinces/municipality in China were investigated by high-performance liquid chromatography–tanden mass spectrometry. The results indicated that perchlorate displays a mean level of 17.17 μg/kg in unhusked rice samples. Intriguingly, we also found that perchlorate is mainly observed in rice husk among these collected unhusked rice samples, while less observed in rice bran and milled rice. Specifically, the perchlorate levels in rice were found in the husks (73.61%), bran (10.09%), and milled rice (19.52%), respectively. Our results indicated that there is no significantly perchlorate exposure risk in edible milled rice.

Carotenoids are the main pigments responsible for the coloration and account for the major antioxidant activity of tomato (Solanum lycopersicum L.) fruit. Significant increments in total carotenoids and lycopene levels were observed in tomato fruit illuminated by red light relative to white light in previous studies, but the mechanism of carotenoid biosynthesis regulated by red light is still unclear. In the present study, the influence of red light on carotenoid biosynthesis in postharvest tomato fruit was conducted using targeted metabolomics and transcriptomic methods. A total of 25 differentially accumulated carotenoids and 1939 differentially expressed genes were isolated and identified. The results illustrated that the contents of phytoene and lycopene were considerably higher in fruit treated with red light than those with white light at 12 h. These differentially expressed genes are mainly enriched in plant hormone signal transduction, photosynthesis, secondary metabolite biosynthesis, and plant circadian rhythm. Moreover, from the results of coexpression network analysis, 15 transcription factors from red light-treated fruit were screened; among these, transcription factors of SlERF4, SlbHLH93 and SlIAA29, which are involved in signal transduction of light and hormones, respectively, may also play important roles in carotenoid biosynthesis regulated by red light in tomato fruit. It is concluded that red light enhanced carotenoid biosynthesis in postharvest tomato fruit and the mechanisms of enhanced carotenoid biosynthesis were not only associated with the direct regulation by red light signalling, but also with the indirect regulation by hormonal signalling.

Objectives Peach (Prunus persica L.) is an ancient fruit tree that originated from China. It is the climacteric fruit belonging to genus Prunus in family Rosaceae. Ethylene, which is produced during ripening, accelerates fruit softening, and therefore peaches cannot be stored for a long time. Materials and Methods To study the mechanism of fruit late ripening, transcriptome analysis of the fruit of a late-ripening mutant of ‘Jinghong’ peach was performed to identify genes and pathways involved in fruit late ripening. Results A total of 1805, 1511, and 2309 genes were found to be differentially expressed in W2_vs_M1, W3_vs_M2, and W3_vs_M3, respectively. Functional enrichment analysis of the differentially expressed genes showed they were related to carotenoid biosynthesis, starch and sucrose metabolism plant hormone signal transduction, flavonoid biosynthesis, and photosynthesis. The expression trends of ripening-related genes that encode transcription factors and plant hormone signal transduction-related genes that encode enzymes were similar. Conclusions It will help to elucidate the transcriptional regulatory network of fruit development in the spontaneous late-ripening mutant of ‘Jinghong’ peach and provide a theoretical basis for understanding the molecular regulatory mechanism of fruit ripening.