•The quality of chestnuts was rapidly evaluated using NIR spectroscopy.•LDA model was successful for the discrimination of mildewed chestnuts.•Contents of water and water-soluble sugars were rapid analyzed using PLS.Near-infrared (NIR) diffuse reflectance spectroscopy was used to evaluate the quality of fresh chestnuts, which can be affected by mildew, water, and levels of water-soluble sugars. The NIR spectra were determined and then modeling was performed including principal component analysis – discriminant analysis (PCA-DA), soft independent modeling of class analogy (SIMCA), linear discriminant analysis (LDA), and partial least squares (PLS) methods. LDA model was better than PCA-DA model for the discrimination of normal and mildewed chestnuts, and the accuracy rates of calibration and validation were 100% and 96.37%, respectively. Normal and mildewed chestnuts were easily distinguished by the SIMCA classification and showed only 4.7% overlap. A PLS model was established to determine the water and water-soluble sugars in chestnuts. The R2 of calibration and validation were all higher than 0.9, while the root mean square errors (RMSE) were all lower than 0.05, indicating that the established models were successful.

•Roasting and frying had similar effects on the nutritional compositions of chestnut.•The main nutritional compounds decreased after cooking.•Asp, Glu and Arg were the main decreased free amino acids in cooked chestnut.•Furfural, ketones and furans formed in cooked chestnuts.This study aimed to evaluate the effects of different cooking methods on the content of important nutrients and volatiles in the fruit of Chinese chestnut. The nutritional compounds, including starch, water-soluble protein, free amino acids, reducing sugar, sucrose, organic acids and total flavonoids, of boiled, roasted and fried chestnuts were significantly (P < 0.05) lower than those of fresh chestnuts after cooking, while the amylose, fat, crude protein and total polyphenol content varied slightly (P > 0.05). l-Aspartic acid, l-glutamic acid and l-arginine were found to be the main reduced free amino acids in cooked chestnuts. The main aromatic compositions in fresh chestnuts were aldehydes and esters, while ketones, furfural and furan were formed in cooked chestnuts due to the Maillard reaction and degradation of saccharides, amino acids and lipids. Principle component analysis demonstrated that roasting and frying had a similar effect on the nutritional composition of chestnuts, which differed from that of the boiling process.

•The physicochemical properties of chestnut starch after cooking were evaluated.•The microstructure of starch was destroyed during thermal processing.•The starch in cooked chestnut still exhibited C-type XRD with weaker intensity.•Roasted chestnut exhibited better texture characterizations than boiled chestnut.•Roasting is an alternative industrial thermal processing method for chestnut kernel.The present study focused on the effect of thermal processing on the physicochemical properties of chestnut starch and textural profile of chestnut kernel. After thermal processing, the total starch content in both boiled and roasted chestnuts decreased significantly (P < 0.05), while the amylose content of boiled chestnut increased and that of roasted chestnut remained stable. The granular microstructure of the starch in cooked chestnut was gradually destroyed during the thermal processing. The starch in cooked chestnut still exhibited C-type X-ray diffraction patterns, but the intensity of diffraction peaks and the crystallinity were obviously declined compared with those of fresh chestnut. Textural profile analysis of chestnut starch gel and chestnut kernel showed that the main textural characterizations of roasted chestnut were higher than those of boiled chestnuts. These results are helpful for better understanding the texture change in fresh, boiled and roasted chestnuts, which indicated that roasting is an alternative industrial thermal processing method for chestnut kernel.

•Salicylic acid can inhibit enzymatic browning of fresh-cut Chinese chestnut.•Salicylic acid can decline the activity of polyphenol oxidase in chestnut.•We determine the inhibition modes by Lineweaver–Burk plots.•We build the binding modes by AUTODOCK.•Salicylic acid is a competitive inhibitor of polyphenol oxidase.The inhibitory effect and associated mechanisms of salicylic acid (SA) on the browning of fresh-cut Chinese chestnut were investigated. Shelled and sliced chestnuts were immersed in different concentrations of an SA solution, and the browning of the chestnut surface and interior were inhibited. The activities of polyphenol oxidase (PPO) and peroxidase (POD) extracted from chestnuts were measured in the presence and absence of SA. SA at concentrations higher than 0.3 g/L delayed chestnut browning by significantly inhibiting the PPO activity (P < 0.01), and the POD activity was not significantly affected (P > 0.05). The binding and inhibition modes of SA with PPO and POD, determined by AUTODOCK 4.2 and Lineweaver–Burk plots, respectively, established SA as a competitive inhibitor of PPO.

•FTIR and chemometrics were used to detect the authenticity of walnut oil.•FTIR and chemometrics were used to detect the adulteration of walnut oil.•The classification limit of soybean oil adulterated in walnut oil by FTIR was 10%.•Fluorescence spectroscopy was used to detect the adulteration of walnut oil.•The classification limit detected by fluorescence spectroscopy was less than 5%.Fourier transform infrared (FTIR) and fluorescence spectroscopy combined with soft independent modeling of class analogies (SIMCA) and partial least square (PLS) were used to detect the authenticity of walnut oil and adulteration amount of soybean oil in walnut oil. A SIMCA model of FTIR spectra could differentiate walnut oil and other oils into separate categories; the classification limit of soybean oil in walnut oil was 10%. Fluorescence spectroscopy could differentiate oil composition by the peak position and intensity of emission spectrum without multivariate analysis. The classification limit of soybean oil adulterated in walnut oil by fluorescence spectroscopy was below 5%. The deviation of the prediction model for fluorescence spectra was lower than that for FTIR spectra. Fluorescence spectroscopy was more applicable than FTIR in the adulteration detection of walnut oil, both from the determination limit and prediction deviation.

•A new bimodal micro-mesoporous Zr-metal organic framework was synthesized.•The force between the support and laccase relies on physical adsorption and aperturing.•The characteristics demonstrate good stability of the laccase-support and support.•The bimodal pores lead to high adsorption without inactivation.•The immobilized laccase shows better activity and a wider utilization range.A new bimodal micro-mesoporous Zr-metal organic framework (Zr-MOF, MMU) with a particle size of approximately 200 nm was synthesized. The Brunauer–Emmett–Teller (BET) surface area and pore diameter of the nanoscale MMU were 453.8 m2/g and 3.5–7 nm, respectively. Laccase was immobilized onto MMU via physical adsorption. This immobilized system exhibited a large adsorption capacity (221.83 mg/g), broad pH and temperature profiles, and better stability and repeatability than free laccase. Inactivation of the interaction between the overcrowded laccase at high concentration and pore plugging were not observed due to the secondary pore structure (3.5 nm). The immobilized laccase showed better stability under extreme conditions than free laccase. The activity of immobilized laccase after utilization 10 times remained at approximately 50%, and it remained at 55.4% of its initial activity at the end of 3 weeks of storage in an aqueous phase. The good stability and retention of enzymatic activity indicated that the bimodal mesoporous Zr-MOF is a good support for the immobilization of laccase.Download full-size image