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Chestnut is widely cultivated and has high nutritional value due to its richness in polysaccharides. In order to improve the antioxidant activity of chestnut polysaccharide, chestnut polysaccharide (CP) was extracted by ultrasonic-assisted water extraction and alcohol precipitation and purified by cellulose DEAE-52 exchange and Sephadex G-100 chromatography in this study. CP isolates were characterized by I2-KI reaction, three-strand helical structure analysis, infrared spectrum analysis, and nuclear magnetic resonance detection. The results showed that CP is a pyrylan sugar with triple helical structure and connected by α-glycosidic bonds, with sugar residues 1,4-α-D-Glcp, 1,6-α-D-Galp, 1,5-α-L-Araf, 1,4-α-L-Rhap, and 1,4-β-D-Glcp in the CP backbone. After purification, the branching structure, rod, and spherical structure were significantly increased, with reduced lamellar structure. The in vitro scavenging rates of CP at 10 mg·mL−1 against DPPH, hydroxyl radicals, and ABTS were 88.95, 41.38, and 48.16%, respectively. The DPPH free radical scavenging rate of purified polysaccharide fraction CP-1a was slightly enhanced, and the other rates showed a small decrease. Selenized chestnut polysaccharide (CP-Se) was prepared using nano-selenium method. The selenization method was optimized and stable Se-CP was obtained. When the concentration was 5 mg·mL−1, Se-CP had significantly higher scavenging abilities 89.81 ± 2.33, 58.50 ± 1.60, and 40.66 ± 1.91% for DPPH, hydroxyl radical, and ABTS radicals, respectively, than those of CP. The results of this study provide insight into the effects purification and selenization of chestnut polysaccharide on antioxidant activity, and also provide a theoretical basis for the development of chestnut polysaccharide for use in functional foods or health products.

In order to identify more suitable thawing method to preserve aroma, taste, and other sensory quality of raspberry, five thawing methods were used to treat frozen raspberry, namely water bath thawing, microwave thawing, ultrasonic thawing, room temperature thawing, and refrigeration thawing. Gas chromatography‐mass spectrometry was employed to study the quantitative and qualitative analysis of the volatile compounds, and the characteristic flavor components of raspberry were compared by relative odor activity value (ROAV). Electronic tongue technique and fuzzy comprehensive evaluation were used to ensure the changes in sensory qualities of raspberry. The results showed that the time of microwave thawing was 0.57 minutes, and drip loss was 4.40%. Both of them were the lowest among the five thawing methods. The volatile components of raspberry included aldehydes, esters, ketones, alcohols, fatty acids, terpenes, and other compounds. Among them, there were 19 kinds of volatile components in quick‐frozen raspberries, 18 volatile components in raspberries after treated by microwave thawing and refrigeration thawing, 16 volatile components after room temperature thawing, 12 volatile components after ultrasonic thawing, and 10 volatile components after water bath thawing. The characteristic flavor compounds of raspberry were identified as acetaldehyde, alpha‐ionone, beta‐ionone, raspberry ketone, alpha‐terpene, and alpha‐pinene. Microwave thawing was the most suitable way to preserve the characteristic flavor components of raspberry, but water bath thawing could destroy the most of compounds. After microwave thawing, raspberry tasted best and was most acceptable to consumers. Therefore, microwave thawing was the most appropriate method to preserve raspberry flavor and sensory quality among the five thawing methods.

Background: Cucumber target leaf spot (TLS), caused by Corynespora cassiicola (C. Cassiicola), is a serious disease in cucumber (Cucumis sativus) production worldwide. Therefore, cultivating new varieties of TLS resistance of C. sativus is an important goal of cucumber breeding. Previous studies have shown that subtilisin-like protease (SUBP) plays an important role in response to C. Cassiicola infection in resistant plants. Objective: In this study, the full-length cDNA of the CsSUBP gene was cloned, and the prokaryotic expression vector was successfully constructed in order to study the effects of subtilisin. Futhermore, vital clues regarding CsSUBP gene involved in TLS resistance of C. sativus are gained from the bioinformatics assay. Method: The CsSUBP gene was identified by sequencing with the intermediate vector pMD18 by designing specific primers and PCR amplification techniques. The prokaryotic expression vector pET30a-CsSUBP was further constructed and identified by colony PCR and EcoR V and SalⅠ double digestion. Result: The primary structure of CsSUBP was predicted and analyzed by bioinformatics analysis. The results showed that CsSUBP was weakly acidic protein, N-terminal signal peptide region, including a Inhibitor_I9 domain domain. Conclusion: The pET30a-CsSUBP prokaryotic expression vector was constructed successfully. This study is convenient for the study of prokaryotic expression and its kinase activity.

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