The influence of gamma irradiation on the storage quality of bamboo shoots

Influence of flowering on the anatomical structure, chemical components and carbohydrate metabolism of Bambusa tuldoides culms at different ages

Bamboo forests, which have come to occupy large areas in recent years, naturally undergo the process of blooming. However, bamboo culms and rhizomes degenerate after the plants bloom, resulting in widespread loss of raw materials. Systematic research on the properties and physiology of bamboo culms after flowering is lacking, and whether flowering bamboo culms could be used as raw materials in industry is unclear. In this paper, we compared and measured the fiber morphology, chemical components, and sugar metabolism indexes of non-flowering and flowering Bambusa tuldoides culms at different ages. The results showed that the fibers in the middle internodes of both non-flowering and flowering B. tuldoides culms had the longest length. The fibers completed their elongation within 1 year, but the fiber walls were continually deposited with age. The levels of the chemical components in the nonflowering culms also continually increased with age. The nonstructural carbohydrate (NSC) content and sugar metabolism indexes showed the highest levels in the 2-year culms and then declined in the 3-year culms. Compared to young culms that had not yet flowered, the 3-month-old and 1-year-old flowering culms had a significant decrease in the fiber length and tangential diameter, and their holocellulose and lignin levels also decreased, while the levels of ash, SiO2, 1% NaOH extractives, and benzene-ethanol extractives increased. A correlation analysis showed that sugar catabolism was accelerated in the flowering cluster, which could lead to "starvation death" in bamboo and which had a significant negative impact on the anatomical and chemical properties of the bamboo culms. Generally, the flowering bamboo culms had shorter fibers, higher levels of extractives and ash, and lower holocellulose content, which indicated that bamboo flowering has an adverse effect on the application of such components in the production of pulp, in papermaking, and in other processing and utilization activities. This study revealed the physiological changes in flowering B. tuldoides culms and provided a theoretical basis to inform the utilization of culms in this species.

Multifaceted analyses reveal carbohydrate metabolism mainly affecting the quality of postharvest bamboo shoots

Bamboo shoot is one of nutritious vegetables in China. However, the edible quality of fresh bamboo shoots deteriorates easily after harvest. Here, morphological, physiological, transcriptomic and microRNA sequencing analyses were conducted to investigate the postharvest characteristics of moso bamboo (Phyllostachys edulis) shoots. Rapid decreases of soluble sugars, structural polysaccharides and hydrolyzed tannins, and increases of lignin and condensed tannins were observed in the postharvest bamboo shoots. Differentially expressed genes (DEGs) and miRNAs with opposite trends were mainly enriched in structural polysaccharide metabolism, starch and sucrose metabolism and glycolysis pathways, which were consistent with the changes of carbohydrates. A co-expression network of carbohydrate metabolism was constructed, which was verified by qPCR and yeast one-hybrid (Y1H) assay. Furthermore, the function of one hub glycosyltransferase gene was validated in Arabidopsis, which confirmed that it was involved in xylan biosynthesis. These results are of great significance for revealing the carbohydrate metabolism mechanisms of postharvest bamboo shoots and provide a potential candidate gene for molecular breeding related to xylan in the future.

Effects of modified atmosphere packaging on the postharvest quality of mulberry leaf vegetable

Fresh mulberry leaf vegetable is nutritive and becoming popular. However, available preservation technologies are deficient. In present work, the effects of two kinds of modified atmosphere packaging on postharvest quality of fresh mulberry leaf vegetable stored at 4 °C were evaluated. The respiration rate of samples in the modified polyethylene packages (MP20) was 12.88-22.65% lower than that in normal polyethylene packaging (CK). The content of total soluble solids, soluble protein, and total polyphenol in MP20 was less changed than that in CK, and the vitamin C retention was higher as well. Moreover, the lignin content in MP20 was lower than that in CK during storage (19.79% vs 13.38% at day 8), and that was significantly positively related to the polyphenol oxidase and peroxidase activities inhibition. Taken together, a packaging with moderate gas permeability (MP20) is suitable for nutrition maintenance and lignification inhibition of fresh mulberry leaf vegetable during cold storage.

Effect of High-Temperature Hydrothermal Treatment on Chemical, Mechanical, Physical, and Surface Properties of Moso Bamboo

Bamboo is an ideal material as it is green, fast-growing, and easy to process. However, the low dimensional stability may limit the application of bamboo due to its richness in hydrophilic groups. Thus, an effective and environment-friendly modification is needed to solve the aforementioned problems. This study employed high-temperature hydrothermal treatment for the modification of bamboo to offer technical support to further promote the application of bamboo materials. Bamboo was heated at various temperatures (120 °C–160 °C) for diverse durations (60–120 min), and the chemical composition, mechanical properties, dimensional stability, and surface color were studied. Results revealed that the parenchyma cells of bamboo were deformed and the parenchymal cell lumen without starch granules after treatment at 160 °C for 120 min. The cellulose and hemicellulose content of bamboo decreased, and the lignin content increased in relative terms as the temperature and time of high-temperature hydrothermal treatment continued to rise. The mechanical properties of bamboo declined after high temperature hydrothermal treatment, and the modulus of rupture (MOR) and modulus of elasticity (MOE) of bamboo at 160 °C for 120 min decreased by 47.11% and 16.14%, respectively, compared to untreated bamboo. The swelling test indicated that the dimensional stability of the bamboo was improved, and the swelling ratio of the bamboo was reduced through the high-temperature hydrothermal treatment. The tangential and radial swelling coefficients of bamboo were reduced by 53.28% and 53.59%, respectively, after treatment at 160 °C for 120 min compared to untreated bamboo. The bamboo surface color was darkened after heat treatment, which gives the bamboo better surface decorative properties.

Zizania latifolia Cell Wall Polysaccharide Metabolism and Changes of Related Enzyme Activities during Postharvest Storage

The metabolism of polysaccharides in the Zizania latifolia cell wall helps maintain the postharvest quality during storage. Fresh Z. latifolia was stored at 4 °C and 25 °C to evaluate the hardness, cell wall polysaccharide composition, cell wall structure, active ingredients, and cell wall metabolism-related enzyme activities. The results showed that hardness declined concomitantly with an increase in water-soluble pectin content during storage, as well as with a decrease in propectin and cellulose contents. Correlation analysis showed that lower activities of cell wall-degrading enzymes, such as polygalacturonase, cellulase, and β-galactosidase in Z. latifolia stored at 4 °C, were associated with lighter fiberization and greater hardness, compared with those stored at 25 °C. Additionally, the results of infrared spectroscopy showed that texture softening may be attributed to a decrease in the degree of esterification of water-soluble polysaccharides at 25 °C compared to that at 4 °C.

Extraction, isolation and identification of four phenolic compounds from Pleioblastus amarus shoots and their antioxidant and anti-inflammatory properties in vitro

Pleioblastus amarus (P. amarus) shoots, belong to the grass family Gramineae, a traditional green vegetable in China, are rich in nutritional properties, and can provide various health benefits. This study isolated four compounds, namely (1-4), 3-O-coumaroylquinic acid (1), 3-O-feruloylquinic acid (2), 4-O-feruloylquinic acid (3), and 5-O-feruloylquinic acid (4) from Pleioblastus amarus shoots for the first time. The structures of the extracted compounds were determined using detailed spectroscopic (1D/2D NMR), high resolution electrospray ionization mass spectrometry (HR-ESI-MS), and infrared (IR) spectroscopy. The antioxidant capacity of 3-O-feruloylquinic acid (2) was stronger than that of the other compounds, while it also exhibited anti-inflammatory activity, significantly restricting the release of nitric oxide (NO) by lipopolysaccharide (LPS)-induced RAW 264.7 cells, displaying an inhibitory rate of 60.92 percent at a concentration of 400 μg/mL. Furthermore, 3-O-feruloylquinic acid (2) inhibited interleukin-1β (IL-1β), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor-κB (NF-κB) expression and may be useful for developing novel antioxidant and anti-inflammatory substances.

Physiological Changes of Bamboo (Fargesia yunnanensis) Shoots During Storage and the Related Cold Storage Mechanisms

The mechanisms for physiological senescence in bamboo shoots after harvest remain unclear. This study investigated physiological changes in Fargesia yunnanensis shoots during storage at different temperatures. The relationship between morphological and physiological changes in bamboo shoots during storage was also analyzed. The results show that cold storage can reduce weight loss, browning, respiration rates, and sugar degradation in bamboo shoots; decrease related enzymatic activities; and inhibit the increase in lignin and cellulose content. The quality of bamboo shoots declines more during the first 3d after harvesting than it does during subsequent periods. The increase in the degree of lignification and fibrosis is the main reason for senescence and for the decline in quality of bamboo shoots after harvest. The bamboo shoots under RT conditions began browning during the third 3d of storage, with a browning rate of 688gkg^-1 even in the upper parts; the increase in shoot browning degrees significantly decreased the quality. Low temperatures had better inhibitory effects on browning than they did on lignification and fibrosis. Nonstructural carbohydrates in bamboo shoots are degraded and flow into sheath and shoot respiration, phenols, and shoot fibrosis and lignification at room temperature, but only flow into sheath respiration, shoot fibrosis, and lignification at cold temperature. Soluble protein and free amino acids are primarily distributed into shoot and sheath respiration and into phenols at room temperature, but that process is well inhibited at cold temperature. Bamboo shoots, once removed from cold storage, should be consumed rapidly because enzyme activity recovers quickly. This research provides new theoretical information on the preservation of bamboo shoots.

Nitric oxide alleviates lignification and softening of water bamboo (Zizania latifolia) shoots during postharvest storage

Water bamboo shoots quickly deteriorate after harvest as a result of rapid lignification and softening. Nitric oxide (NO) has been used to extend the postharvest life of several other vegetables. Here, we examined the effect of NO on the storage of water bamboo shoots at 4℃ for 28 days. Without NO, fresh weight and firmness decreased quickly, while the cellulose and lignin contents increased sharply during storage. NO treatment delayed softening by maintaining the integrity of the cell wall and inhibiting the degradation of protopectin and the expressions of pectin methylesterase and polygalacturonase. NO treatment also delayed cellulose synthesis by increasing cellulase activity. NO treatment decreased the synthesis of lignin by inhibiting the activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, laccase and peroxidase. These results indicate that NO treatment is effective at suppressing the softening and lignification of water bamboo shoots during postharvest storage.

Postharvest benzothiazole treatment enhances healing in mechanically damaged sweet potato by activating the phenylpropanoid metabolism

BACKGROUND

Sweet potato often suffers mechanical damage during harvest, handling, and transportation. Infections, water loss, and quality changes of sweet potato caused by mechanical damage pose great financial losses. Wound healing is an effective method to alleviate such problems. In this study, the effects of postharvest treatment with benzothiazole (BTH) on wound healing of sweet potato was investigated.

RESULTS

Postharvest BTH treatment of sweet potatoes promoted lignin accumulation in wounded tissues, and 100 mg L^-1 BTH exhibited better effects than 50 mg L^-1 or 150 mg L^-1 BTH. The biosynthesis of lignin in wounded tissues significantly decreased the weight loss of sweet potatoes. An increase in respiration intensity after BTH treatment was observed. The total phenolic and flavonoid contents and the activity of phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase were increased in BTH-treated sweet potatoes. This suggests that BTH increases phenylpropanoid metabolism.

CONCLUSION

Postharvest 100 mg L^-1 BTH treatment could promote wound healing in mechanically damaged sweet potatoes. The activation of the phenylpropanoid metabolism might be the mechanism of action of BTH in wound healing. © 2020 Society of Chemical Industry.