Effects of trisodium phosphate treatment after harvest on storage quality and sucrose metabolism in jujube fruit

Transcriptome Analysis Reveals the Mechanism of Cold-Induced Sweetening in Chestnut during Cold Storage

Chestnuts become sweetened with better tastes for fried products after cold storage, but the possible mechanism is not clear. The dynamics of sugar components and related physiological responses, as well as the possible molecular mechanism in chestnuts during cold storage, were investigated. Sucrose accumulation and starch degradation contributed to taste improvement. Sucrose content reached the peak after two months of cold storage, along with the accumulation of reducing sugars of maltose, fructose and glucose to a much lesser extent. Meanwhile, alpha-amylase and beta-amylase maintained high levels, and the activities of acid invertase and sucrose synthase increased. Transcriptome data demonstrated that differentially expressed genes (DEGs) were significantly enriched in the process of starch and sucrose metabolism pathway, revealing the conversion promotion of starch to sucrose. Furthermore, DEGs involved in multiple phytohormone biosynthesis and signal transduction, as well as the transcription regulators, indicated that sucrose accumulation might be interconnected with the dormancy release of chestnuts, with over 90% germinated after two months of cold storage. Altogether, the results indicated that cold storage improved the taste of chestnuts mainly due to sucrose accumulation induced by DEGs of starch and sucrose metabolism pathway in this period, and the sweetening process was interconnected with dormancy release.

Eco-safe hot water dip alleviates antioxidant level and sensory quality of Indian jujube fruits

Indian jujube (Ber) is highly perishable climacteric fruit owing to high decay index limiting its marketability and demands interventions to prolong shelf life. Fungicides are normally used to control rot during postharvest storage, however, residues left necessitate eco-safe alternatives like hot water dipping. Mature, pre-climacteric jujubes were dipped in 45, 50 or 55 °C water for 8, 6 or 4 min, respectively and then stored at 5 °C for periodic quality evaluation. Dipping fruits in 55 °C water resulted in 32.69 and 35.27, 64.21 and 58.57, 30.41 and 30.42, 38.50 and 52.20 % lower weight loss, decay index, malondialdehyde (MDA) and electrolyte leakage, whereas 15.40 and 16.77, 19.51 and 20.48 % greater antioxidant activity and ascorbic acid respectively for Umran and Pakwhite compared to 25 °C water dip. The highest glucose, fructose, malic, citric, and tartaric acids were 23.44 ± 1.04 and 29.9 ± 0.95, 30.68 ± 1.72 and 41.17 ± 2.34 mg/100 g, 138.1 ± 6.45 and 112.97 ± 6.16, 57.49 ± 1.71 and 53.78 ± 1.90, 79.58 ± 5.1 and 65.3 ± 4.83 μg/100 g whereas lower sucrose 12.34 ± 0.94 and 16.33 ± 1.05 mg/100 g were respectively recorded in 55 °C water dipped Umran and Pakwhite fruits. High dip water temperature (55 °C) exhibited better quality with the lowest decay index and weight loss, greater membrane integrity, bioactives content and sensory acceptance scores. Hence, hot water dipping was shown to be an effective residue-free option to extend the marketable period of jujubes to capture distant markets.

Effect of poly(L-lactic acid)/poly(ethylene glycol)-poly(L-lactic acid) block copolymer blend film on preservation of Chinese winter jujube (Ziziphus Jujuba Mill. cv. Dongzao)

The effect of poly(L-lactic acid)/poly(ethylene glycol)-poly(L-lactic acid) block film on preservation of Chinese winter jujube (Ziziphus Jujuba Mill.cv.Dongzao) was investigated. Eight arm poly(ethylene glycol)-poly(L-lactic acid) block copolymer (8-PEG/PLLA) and net structure 8-PEG/PLLA (NET-PEL) were successfully synthetized by ring-opening polymerization, and different percentages (5, 10, and 20 %) of them were blended with PLLA to prepared blends films. Mechanical properties, modulated different scanning calorimetry (MDSC), gas and water vapor permeability results showed that 8-PEG/PLLA and NET-PEL block copolymer greatly increased the toughness of blend films, could be decrease PLLA segment glass transition temperature (Tg)from 59.5 °C to 41.6-46.7 °C and cold crystallization temperature(Tcc)from 89.4 °C to 73.5-77.7 °C, and increased the oxygen (O2), carbon dioxide (CO2), and water vapor transmission rate. The an appropriate gas concentration [O2 (2.56-3.51 %), CO2 (5.05-5.56 %)] was created inside the PLLA/NET-PEL20% (NEPEL20)group, which could restrain increase of total soluble solids (TSS), malonaldehyde content. The firmness, color luminosity (L*), total phenols, and ascorbic acid were maintained at higher level，and kept its commercial value after 40 days of storage. The present data indicated that treating post-harvest winter jujubes with NEPEL20 MAP packaging was an effective method for preservation of postharvest winter jujube.

l-Glutamate maintains the quality of apple fruit by mediating carotenoid, sorbitol and sucrose metabolisms

BACKGROUND

l-Glutamate is involved in many important chemical reactions in horticultural products and improves postharvest disease resistance. Quality decline of apple fruit caused by senescence and fungus invasion often leads to tremendous losses during logistics. This study was performed to evaluate the variations of quality attributes, carotenoid, sorbitol and sucrose metabolisms in apples (cv. Qiujin) after l-glutamate dipping treatment.

RESUITS

l-Glutamate immersion maintained high values of L*, a* and b*, flesh firmness, titratable acidity, as well as the total soluble solids, soluble sugar, reducing sugar and ascorbic acid contents in apples. l-Glutamate also decreased mass loss, respiratory rate and ethylene release, enhanced sucrose synthase-cleavage, acid invertase and neutral invertase activities, whereas reduced sorbitol dehydrogenase, sucrose phosphate synthase, sucrose synthase synthesis and sorbitol oxidase activities in apples. Moreover, l-glutamate inhibited lutein, β-carotene and lycopene accumulation, and down-regulated phytoene synthase, lycopene β-cyclase, ζ-carotene desaturase, phytoene desaturase, carotenoid isomerase, ζ-carotene isomerase and carotenoids cleavage dioxygenase gene expressions, but up-regulated 9-cis-epoxycarotenoid dioxygenase gene expression in apples.

CONCLUSION

Postharvest l-glutamate dipping treatment can keep apple quality by modulating key enzyme activity and gene expression in sorbitol, sucrose and carotenoid metabolisms. © 2023 Society of Chemical Industry.

Abnormal behavior of chilling injury in postharvest papaya fruit is associated with sugar metabolism

In the most chilling-sensitive fruits and vegetables, usually, the lower the storage temperature, the more serious the symptoms of chilling injury (CI). As one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. Such abnormal CI phenomenon has not received enough attention and its mechanism is not clear. The present study investigated the difference of CI severity and sugar metabolism in papaya fruits when stored between 1℃ and 6℃. The results showed that CI index in papaya fruits preserved at 1°C was markedly lower than that in fruit at 6°C, which was accompanied by higher content of glucose, fructose, and sucrose. In addition, compared to 6°C, 1°C promoted higher activities of sucrose synthase, sucrose-phosphate synthase, and neutral invertase, but lowered acid invertase activity. RT-qPCR analysis showed that 1°C upregulated the CpSPS expression and downregulated the CpAI expression when compared to 6°C. The present results indicate that higher chilling tolerance in papaya fruit at 1°C could be attributed to more accumulation of sucrose and reducing sugars in relation to more advantageous sugar metabolism. These results provided a basis for explaining the abnormal behavior of papaya fruits in response to varying low temperatures. PRACTICAL APPLICATION: For most chilling-sensitive fruits and vegetables, in the range of temperatures that induce chilling injury (CI), the lower storage temperature may lead to more severe CI. However, as one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. The reason for this abnormal CI symptom in papaya fruits is that 1°C storage can regulated enzyme activities and changes in gene expression related to sugar metabolism, which could result in more accumulation of sucrose and slower degradation of hexose and contribute to alleviation of CI. Our results provided a basis for explaining the abnormal behavior of papaya fruit in response to varying low temperatures.

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 quality and color of winter jujube fruits are easy to change after harvest. We studied the regulation mechanism of propyl gallate (PG) on post-harvest physiological quality of winter jujube, from the perspective of antioxidant metabolism and peel structure. In our research, winter jujube fruits were treated with 0.001 mol L⁻¹ PG solution for 20 min. Our results showed that PG delayed the development of peel color, and improved the firmness, total soluble solids (TSS), and titratable acid (TA) of winter jujube. Meanwhile, the PG treatment had higher content of total phenols, total flavonoids, ascorbic acid (AsA), and reduced glutathione (GSH), and kept the enzyme activity including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) at a higher level. PG treatment reduced membrane oxidative damage and maintained the integrity of pericarp structure by reducing electrolyte leakage (EL), lipoxygenase activity (LOX), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) content in the peel. Accordingly, PG improved the postharvest quality of jujube fruits by regulating antioxidant metabolism and maintaining the structure of peel. The appropriate concentration of PG has good application potential in the storage and preservation of fresh fruits such as winter jujube.

Heat shock treatment maintains the quality attributes of postharvest jujube fruits and delays their senescence process during cold storage

The effects of heat shock (HT), 1-methylcyclopropene (1-MCP), or their combination (HT + 1-MCP) on the quality of fresh jujube fruits during cold storage were studied. Among them, HT showed the best preservation effect on jujube fruits, which was more effective than others in inhibiting the increase of red index, decay incidence, and weight loss and delaying the decrease of firmness, soluble solids content (SSC), titratable acidity (TA), and ascorbic acid (AsA) content. Besides, it could delay the degradation rate of the cell wall to maintain the integrity of cell membrane, and keep the high activity of active oxygen scavenging enzymes. During cold storage, malondialdehyde (MDA) content and relative electrolyte leakage (REL) of the HT group were significantly lower than those of the control group, 1-MCP, and HT + 1-MCP group (p < .05), while superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were significantly higher than those of other groups (p < .05). It was concluded that the postharvest HT treatment could effectively delay the senescence and decay of jujube fruits. PRACTICAL APPLICATIONS: Jujube fruits have high nutritional value used for food and medicine. However, they are not tolerant to storage after harvest, resulting in high economic losses. Therefore, it is of great significance to find a suitable method to maintain the quality of jujube fruits. Our results revealed the effect of HT, 1-MCP, and their combination on the quality maintenance of jujube fruits, and found that HT could effectively maintain the quality of them, which could be used as an effective method for keeping jujube fruits fresh.

Gene expression profiling reveals the effects of light on adventitious root formation in lotus seedlings (Nelumbo nucifera Gaertn.)

BACKGROUND

Lotus is an aquatic horticultural crop that is widely cultivated in most regions of China and is used as an important off-season vegetable. The principal root of lotus is degenerated, and adventitious roots (ARs) are irreplaceable for plant growth. We found that no ARs formed under darkness and that exposure to high-intensity light significantly promoted the development of root primordia. Four differential expression libraries based on three light intensities were constructed to monitor metabolic changes, especially in indole-3-acetic acid (IAA) and sugar metabolism.

RESULTS

AR formation was significantly affected by light, and high light intensity accelerated AR development. Metabolic changes during AR formation under different light intensities were evaluated using gene expression profiling by high-throughput tag-sequencing. More than 2.2 × 104 genes were obtained in each library; the expression level of most genes was between 0.01 and 100 (FPKF value). Libraries constructed from plants grown under darkness (D/CK), under 5000 lx (E/CK), and under 20,000 lx (F/CK) contained 1739, 1683, and 1462 upregulated genes and 1533, 995, and 834 downregulated genes, respectively, when compared to those in the initial state (CK). Additionally, we found that 1454 and 478 genes had altered expression in a comparison of libraries D/CK and F/CK. Gene transcription between libraries D/F ranged from a 5-fold decrease to a 5-fold increase. Twenty differentially expressed genes (DEGs) were involved in the signal transduction pathway, 28 DEGs were related to the IAA response, and 35 DEGs were involved in sugar metabolism. We observed that the IAA content was enhanced after seed germination, even in darkness; this was responsible for AR formation. We also observed that sucrose could eliminate the negative effect of 150 μMol IAA during AR development.

CONCLUSIONS

AR formation was regulated by IAA, even in the dark, where induction and developmental processes could also be completed. In addition, 36 genes displayed altered expression in carbohydrate metabolism and ucrose metabolism was involved in AR development (expressed stage) according to gene expression and content change characteristics.