Propyl Gallate Treatment Improves the Postharvest Quality of Winter Jujube (Zizyphus jujuba Mill. cv. Dongzao) by Regulating Antioxidant Metabolism and Maintaining the Structure of Peel

The effect of cold plasma treatment on the fruit quality and aroma components of winter jujubes (Ziziphus jujuba Mill. 'Dongzao')

Cold plasma (CP) is a novel environmental-friendly preservation technology that causes minimal damage to fruits. The flavor and quality of winter jujubes have decreased with the extended storage time. Currently, the research on the use of CP on winter jujubes (Ziziphus jujuba Mill. 'Dongzao') mainly focuses on the effect of the treatment on storage quality. There is limited research on the effect of CP treatment on the flavor of winter jujubes. This study used different CP (80 kV) treatment durations (0, 5, and 10 min) to treat winter jujubes. The appropriate treatment time was selected by observing the changes in color, respiratory intensity, soluble sugar content, total acid content, and vitamin C (VC) content of winter jujubes. Amino acid analyzer and headspace solid-phase microextraction in combination with gas chromatography coupled with mass spectrometric detection were used to analyze the effect of CP treatment on the flavor compounds of winter jujubes. The results showed that the 5-min CP treatment could significantly slow down the red coloration of winter jujube while maintaining high soluble sugar, total acid, and VC content. At the respiration peak, the respiratory intensity of the 5-min CP treatment group was 0.74 mg CO2·kg-1·h-1 lower than that of the control group (p < 0.05). CP treatment slowed down the decrease in the content of amino acids and volatile organic compounds (such as 2-methyl-4-pentenal, 2-hexenal, and 3-hexenal) in winter jujubes. This study will provide basic data for applying CP preservation technology in postharvest winter jujubes.

Hot water mobilizes the metabolism of energy, soluble sugar, cell wall, and phenolics to cope with chilling injury in postharvest snap beans

BACKGROUND

Snap beans (Phaseoulus vulgaris L.) are very sensitive to low temperature during postharvest storage. Pitting, rusting, and water-soaked patches are typical chilling injury (CI) symptoms of snap beans. The appearance of these symptoms reduces the storage quality of snap beans. The energy, soluble carbohydrates, cell wall, and phenolic metabolisms of refrigerated snap beans and their relationship to CI treated with 35 °C hot water (HW) were investigated.

RESULTS

HW treatment reduced CI index and electrolyte leakage and increased the contents of soluble solids, titratable acidity, and chlorophyll. HW treatment maintained higher activities of proton ATPase, calcium ATPase, and cytochrome c oxidase, which resulted in the accumulation of more adenosine triphosphate, adenosine diphosphate, and energy charge. The accumulation of soluble sugar induced by HW treatment was correlated with the stimulation of sucrose phosphate synthase and sucrose synthase. The prevention effect of HW treatment on the degradation of cell wall components was related to the inhibition of pectin methylesterase and cellulase. HW-induced phenol accumulation is associated with an increase in shikimate dehydrogenase, phenylalanine ammonia lyase, cinnamate-4-hydroxylase, and 4-coumarine-coenzyme A ligase, as well as a decrease in polyphenol oxidase.

CONCLUSION

The alleviating effect of HW on CI is due to its regulation of energy, soluble sugar, cell wall, and phenolic metabolism. Therefore, HW treatment may be an effective means to reduce CI of snap beans. © 2024 Society of Chemical Industry.

Quality Changes and Fungal Microbiota Dynamics in Stored Jujube Fruits: Insights from High-Throughput Sequencing for Food Preservation

Postharvest rot is an urgent problem affecting the storage of winter jujube. Therefore, the development of new technologies for efficient and safe preservation is very important. This study aimed to elucidate the fungal microbiota found on the epidermis of jujube during the storage period using high-throughput sequencing, as well as to monitor the changes in quality indexes throughout this period. Through internal transcribed spacer (ITS) sequencing, we identified two phyla (Basidiomycota and Ascomycota) and six genera (Cryptococcus, Bulleromyces, Sporidiobolus, Alternaria, Pseudozyma, and Sporobolomyces), which potentially contribute to the spoilage and deterioration of jujube, referred to as "core fungal taxa". A high correlation was further found between preservation indices (including decay rate, firmness, and total soluble solids) and the growth of multiple core fungi over time. These findings will provide insights and a theoretical basis for further research on preservation techniques related to biological control during date fruit storage.

Nisin and ε-polylysine combined treatment enhances quality of fresh-cut jackfruit at refrigerated storage

This study investigated the effects of nisin combined with ε-polylysine on microorganisms and the refrigerated quality of fresh-cut jackfruit. After being treated with distilled water (control), nisin (0.5 g/L), ε-polylysine (0.5 g/L), and the combination of nisin (0.1 g/L) and ε-polylysine (0.4 g/L), microporous modified atmosphere packaging (MMAP) was carried out and stored at 10 ± 1°C for 8 days. The microorganisms and physicochemical indexes were measured every 2 days during storage. The results indicated that combined treatment (0.1 g/L nisin, 0.4 g/L ε-polylysine) had the best preservation on fresh-cut jackfruit. Compared with the control, combined treatment inhibited microbial growth (total bacterial count, mold and yeast), reduced the weight loss rate, respiratory intensity, polyphenol oxidase and peroxidase activities, and maintained higher sugar acid content, firmness, and color. Furthermore, it preserved higher levels of antioxidant compounds, reduced the accumulation of malondialdehyde and hydrogen peroxide, thereby reducing oxidative damage and maintaining high nutritional and sensory qualities. As a safe application of natural preservatives, nisin combined with ε-polylysine treatment has great application potential in the fresh-cut jackfruit industry.

Biochemistry behind firmness retention of jujube fruit by combined treatment of acidic electrolyzed water and high-voltage electrostatic field

Harvested jujube (Zizyphus jujuba Mill) is prone to softening due to active metabolism. This study investigated the effects of acidic electrolyzed water (AEW), high-voltage electrostatic field (HVEF) and their combination (AEW + HVEF) on softening and associated cell wall degrading enzymes (CWDEs), cell membrane integrity and antioxidant system of 'Huping' jujube during storage at 0 ± 1 °C. The results indicated that fruit subjected to AEW + HVEF, AEW or HVEF treatments maintained firmness 15.7%, 10.7%, and 5.3% higher than that of untreated control fruit at the end of 90 days cool storage. Fruit treated with AEW + HVEF could better maintain cell membrane integrity and exhibit lower activities of CWDEs and higher antioxidant capacity than that treated with either AEW or HVEF. Correlation analysis suggested that inhibition of softening was associated with reduction of CWDEs activities, and maintenance of membrane integrity and antioxidant system.

1-Methylcyclopropene Alleviates Postharvest Chilling Injury of Snap Beans by Enhancing Antioxidant Defense System

Research background

Chilling injury is a major disorder affecting the quality of tropical and subtropical vegetables during low temperature storage. Snap bean (Phaseolus vulgaris L.) is sensitive to chilling injury. The main purpose of the present study is to investigate the alleviating effects of 1-methylcyclopropene (1-MCP) on chilling injury of snap bean. In addition, the related mechanisms were also detected from the perspective of the changes of antioxidant defense system.

Experimental approach

Snap beans were exposed to different volume fractions of 1-MCP. After 24 h of treatment, snap beans were stored at 4 °C for up to 14 days. Chilling injury index, electrolyte leakage, titratable acidity and total soluble solids were determined. Contents of chlorophyll, ascorbic acid and malondialdehyde were assessed. The total antioxidant capacity, Fe(II) ion chelating capacity, scavenging capacities on free radicals and activities of antioxidant enzymes were detected. Total phenol content and activities of related metabolic enzymes were also determined.

Results and conclusions

1-MCP treatment reduced chilling injury index, electrolyte leakage rate and malondialdehyde content of snap beans. The amounts of total soluble solids, titratable acid, ascorbic acid and total chlorophyll in 1-MCP-treated snap beans were significantly higher than those of control. The snap beans treated with 1-MCP showed stronger total antioxidant capacity and metal chelating activity. The 1-MCP treatment enhanced scavenging effects of snap beans on superoxide, hydroxyl and 1,1-diphenyl-2-trinitrophenylhydrazine radicals. The activities of peroxidase, ascorbate peroxidase, superoxide dismutase and catalase in 1-MCP-treated group were higher than of control. The treatment also enhanced the accumulation of phenolic compounds in snap beans by regulating the activities of phenol-metabolizing enzymes such as shikimate dehydrogenase, phenylalanine ammonia lyase enzyme, cinnamic acid 4-hydroxylase and polyphenol oxidase. In conclusion, with the mechanism that involves the activation of enzymatic and non-enzymatic antioxidant systems, 1-MCP has the ability to avoid chilling injury of snap bean.

Novelty and scientific contribution

This study gives insights into whether 1-MCP can regulate postharvest cold resistance in vegetables by enhancing the enzymatic antioxidant system and inducing the accumulation of non-enzymatic antioxidants. Considering the results, 1-MCP treatment could be an effective method to alleviate postharvest chilling injury of snap beans during low temperature storage.

Combined Treatment of Acidic Electrolyzed Water and High-Voltage Electrostatic Field Improves the Storage Quality of Huping Jujube (Ziziphus jujuba Mill. cv. Huping)

Fresh jujube is prone to rapid deterioration after harvest due to its active metabolism and rich nutrients. This study aimed to investigate the effects of acidic electrolyzed water (AEW), a high-voltage electrostatic field (HVEF) and a combination of AEW and HVEF (AEW + HVEF) treatments on the storage quality of Huping jujube (Ziziphus jujuba Mill. cv. Huping) stored at 0 ± 1 °C for 90 days. The results showed that the fruits treated with AEW + HVEF exhibited better storage quality than those treated with either AEW or HVEF alone. Specifically, the fruits treated with AEW + HVEF maintained higher levels of nutrients and taste compounds, including total soluble solid (TSS), total soluble sugar, reducing sugar and titratable acidity (TA), as well as lower respiration rate, weight loss, decay index and TSS/TA ratio. Additionally, the AEW + HVEF treatment could delay the increase in reddening index, a* and color change (ΔE) values, and the decrease in L* and b* values, by retarding the degradation of chlorophyll and accumulation of carotenoids and flavonoids, thereby preserving the more desirable appearance color. Furthermore, the combined treatment could enhance the glutathione reductase (GR) activity and 2,2'-azino-bis-(3-ethylbenzothizoline)-6-sulfonic acid (ABTS) +-scavenging ability. Thus, the AEW + HVEF treatment is a potential method for Huping jujube preservation.

CRISPR/Cas9-mediated SNAC9 mutants reveal the positive regulation of tomato ripening by SNAC9 and the mechanism of carotenoid metabolism regulation

NAC transcriptional regulators are crucial for tomato ripening. Virus-induced gene silencing (VIGS) of SNAC9 (SlNAC19, Gene ID: 101248665) affects tomato ripening, and SNAC9 is involved in ethylene and abscisic acid (ABA) metabolic pathways. However, the function of SNAC9 in pigment metabolism in tomatoes remains unclear. This work seeks to discover the mechanism of SNAC9 involvement in pigment metabolism during tomato ripening by establishing a SNAC9 knockout model using CRISPR/Cas9 technology. The results indicated that fruit ripening was delayed in knockout (KO) mutants, and SNAC9 mutation significantly affected carotenoid metabolism. The chlorophyll (Chl) degradation rate, total carotenoid content, and lycopene content decreased significantly in the mutants. The transformation rate of chloroplasts to chromoplasts in mutants was slower, which was related to the carotenoid content. Furthermore, SNAC9 changed the expression of critical genes (PSY1, PDS, CRTISO, Z-ISO, SGR1, DXS2, LCYE, LCYB, and CrtR-b2) involved in pigment metabolism in tomato ripening. SNAC9 knockout also altered the expression levels of critical genes involved in the biosynthesis of ethylene and ABA. Accordingly, SNAC9 regulated carotenoid metabolism by directly regulating PSY1, DXS2, SGR1, and CrtR-b2. This research provides a foundation for developing the tomato ripening network and precise tomato ripening regulation.