•RS and ATR-IR were firstly applied to determine TAC and TPC in Chinese rice wine.•Models based on RS and ATR-IR were systemically compared and discussed.•Combination of RS and ATR-IR were firstly used to predict TAC and TPC in wine.The application of attenuated total reflectance infrared spectroscopy (ATR-IR), Raman spectroscopy (RS) and combination of ATR-IR and RS for measurements of total antioxidant capacity (TAC) and total phenolic content (TPC) of Chinese rice wine (CRW) were investigated in this study. Synergy interval partial least-squares (SiPLS), support vector machine (SVM) and principal component analysis (PCA) were applied to process the merged data from two individual instruments. It was observed that the performances of models based on the RS spectra were better than those based on the ATR-IR spectra. In addition, SVM models based on the efficient information extracted from ATR-IR and RS spectra were superior to PLS models based on the same information and PLS models based on ATR-IR or RS spectra. The overall results demonstrated that integrating ATR-IR and RS was possible and could improve the prediction accuracy of TAC and TPC in CRWs.

•The enzyme increased BD and WSI, while decreased WAI and viscosity of R/S mixture.•Antioxidant activity was improved by the combined addition of soybean and enzyme.•The highest TPC/TFC retention was achieved with soybean added up to 30%.In order to determine the effect of enzymatic extrusion on the physicochemical and antioxidant properties of rice/soybean mixture, different mass ratios (100/0, 95/5, 85/15, 70/30, 50/50 and 25/75%, w/w) were treated with thermostable α-amylase. The reduced special mechanical energy and the enhanced product temperature were closely and regularly linked with the increase of soybean content. The bulk density and water solubility index increased, and the water absorption index and viscosities decreased remarkably after enzymatic extrusion, however, the modification caused by α-amylase were dramatically eliminated with the increase of soybean content to ∼50%. Moreover, the addition of enzyme exhibited an improvement of the total phenolic/flavonoid content (TPC/TFC) and antioxidant capacities compared to traditional extrusion. The TPC/TFC retention of extrudate (ratios of 85/15 and 70/30%) attained over 90%, but dramatically decreased (72.91 and 67.81%, respectively) with soybean added to 75%, probably due to the great reduction of starch substrate for enzymatic hydrolysis.

•Complexation of chitosan and pullulanase was affected by chitosan molecular weight.•Pullulanase was immobilized onto Fe3O4–κ-carrageenan nanoparticles by complexation.•Interrelationship exists between chitosan Mw and binding characteristic.•The high binding affinity induces more alterations of protein secondary structure.•Changes in secondary structures impact enzymatic properties of immobilized enzyme.The interactions between pullulanase and chitosans of different molecular weights (Mw) were comprehensively studied, and their applications in pullulanase immobilization onto Fe3O4–κ-carrageenan nanoparticles upon chitosan–pullulanase complexation were also evaluated. Chitosan (CS) complexation with pullulanase was found to be dependent on pH and chitosan Mw. The critical pH of structure-forming events during complexation shifted significantly (p < 0.05) to a lower pH with a low Mw chitosan (50 kDa) compared to other chitosan types. Binding constants for the chitosan–pullulanase interaction increased in the following order: CS-500 < CS-400 < CS-50 < CS-200. The binding induced alterations in the protein secondary structure, which may affect the enzymatic properties of immobilized pullulanase. Pullulanase immobilized upon CS-50 complexation exhibited the most desirable enzymatic properties. These results indicated that the complexation behavior was mainly dependent on chitosan Mw. This study presents a technique for the production of immobilized pullulanase upon complexation that exhibits potential for applications in continuous syrup production.

•RSM was used to evaluate and optimize the operating conditions of enzymatic extrusion for rice flour.•Severe extrusion conditions resulted in low SME but high starch gelatinization and antioxidant activity.•The retention ratio of total phenolic content in rice significantly increased with increasing moisture and enzyme levels.For the purpose of investigating the effect of enzyme concentration (EC), barrel temperature (BT), moisture content (MC), and screw speed (SS) on processing parameters (product temperature, die pressure and special mechanical energy (SME)) and product responses (extent of gelatinization (GE), retention rate of total phenolic content (TPC-RR)), rice flour extruded with thermostable α-amylase was analyzed by response surface methodology. Stepwise regression models were computed to generate response surface and contour plots, revealing that both TPC-RR and GE increased as increasing MC while expressed different sensitivities to BT during enzymatic extrusion. Phenolics preservation was benefited from low SME. According to multiple-factor optimization, the conditions required to obtain the target SME (10 kJ/kg), GE (100%) and TPC-RR (85%) were: EC = 1.37‰, BT = 93.01 °C, MC = 44.30%, and SS = 171.66 rpm, with the actual values (9.49 kJ/kg, 99.96% and 87.10%, respectively) showing a good fit to the predicted values.

Rapid analysis of Chinese rice wine (CRW) is an important activity for quality assurance and control investigations. In recent years, due to its insensitivity to water and fewer overlapped bands, Raman spectroscopy (RS) may provide more useful qualitative and quantitative information on functional groups of various chemical compounds in CRWs than the conventional spectroscopic technique (e.g., infrared spectroscopy); there has been a growing interest in the application of RS in the qualitative and quantitative analysis in food industry. In this study, the applicability of RS hyphenated with chemometrics using different pretreated spectra was examined to develop rapid, low-cost, and non-destructive method for quantification of four enological parameters involved in CRW quality control. Partial least square (PLS) was used for building the calibration models for the four chemical parameters based on the full RS spectrum. The model was also optimized by using efficient wavelength selection algorithm, i.e., synergy interval partial least square (SiPLS) algorithm. In addition, soft independent modeling of class analogy (SIMCA) and linear discriminant analysis (LDA) were used as classification techniques to predict the brands (wineries) of CRW samples. The results demonstrated that compared with the PLS model using all wavelengths of RS spectra, the prediction precision of model based on the spectral variables selected by SiPLS was significantly improved with high values of the coefficient of determination (>0.90), residual predictive deviation (>3.0), and range error ratio (>10) for all of the four quality parameters. The SIMCA and LDA results, characterized by high percentages of correct classification (96.67 and 100.00 % as average value in prediction for SIMCA and LDA, respectively), showed that samples belonging to a particular brand could be correctly classified. The overall results indicated the suitability of RS combined with efficient variable selection algorithm to rapidly control the quality of CRW.

•Magnetite chitosan/carrageenan nanocomposites were prepared by in situ method.•Magnetic response of nanocomposites to an applied magnetic field was enhanced.•Magnetite nanocomposites with excellent BSA adsorption capacity were obtained.•BSA loaded magnetite nanocomposites released in simulated intestinal medium.We present a simple method to develop magnetite chitosan/carrageenan nanocomposites by in situ synthesis under mild conditions, and then their potential for controlled release of macromolecules was also evaluated. The structural, morphological and magnetic properties of the as-prepared materials were studied by vibrating sample magnetometer, X-ray diffractometer, Fourier transform infrared spectroscopy, thermogravimetric analyzer and transmission electron microscopy. With the varying mass ratio (chitosan to Fe3O4-carrageenan nanocomposite), the developed nanocarriers presented sizes within 73–355 nm and zeta potentials of −42–32 mV. Using bovine serum albumin as model protein, the adsorption and release behaviors were investigated. Nanocarriers evidenced excellent loading capacity of 181 mg g−1 at protein concentration of 0.2 mg mL−1, and demonstrated capacity to provide a sustained release up to 85% of adsorbed protein in 30 min in intestinal medium rather than acidic medium. These results suggest that the developed magnetite chitosan/carrageenan nanocomposites are promising in the application of magnetically targeted delivery of therapeutic macromolecules.

•We treated glutinous rice for Chinese rice wine fermentation using different pretreatments including enzymatic extrusion.•Changes to TPC, free/bound phenolic acids and antioxidant activities were measured by UV–Vis and HPLC methods.•We investigated the physicochemical properties of extruded rice related to the improved TPC and antioxidant activity.The effect of simultaneous extrusion and enzymatic hydrolysis on the phenolics and antioxidant activities of glutinous rice and further fermented Chinese rice wine was investigated. Great modification on rice properties (water absorption/solubility index) related to higher total phenolic content (TPC) retention (87.73%) was determined in enzymatically extruded rice compared to traditionally cooked or extruded rice (37.61–50.85% TPC retention). A total of ten phenolic acids (in free/bound forms) with great loss rates were identified in different treated rice, except the enzymatically extruded rice showing effective inhibition of phenolics loss (only 2.66, 2.04, 22.49, 1.89 and 6.37% loss for total gallic, chlorogenic, vanillic, syringic, and ferulic acids, respectively). After fermentation, the level of p-hydroxybenzoic and p-coumaric acids increased predominantly, while chlorogenic acid dramatically decreased to an extremely low level, indicating a changed chemical proportion of phenolics in Chinese rice wine. Compared with raw rice, enzymatically extruded rice achieved a higher antioxidant activity (DPPH, ABTS, reducing capacity and FRAP), probably due to the synergy of phenolic retention and Maillard-derived products formation. Moreover, this advantage of simultaneous extrusion and enzymatic hydrolysis could be further exhibited in Chinese rice wine products via fermentation processing.

We present a simple method to immobilize pullulanase onto hybrid magnetic (Fe3O4–κ-carrageenan) nanoparticles, involving the in situ synthesis of magnetic carrageenan nanoparticles and the formation of pullulanase/chitosan complex. The complex behavior of pullulanase with chitosan as a function of pH and protein–polysaccharide ratio was studied by turbidimetric titration. Then, the as-prepared immobilized enzymes were characterized by vibrating-sample magnetometer, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer, and thermogravimetric analysis. It was found that the activity retention of immobilized pullulanase and amount of enzyme loaded reached 95.5% and 96.3 mg/g, respectively, under optimal conditions. The immobilized enzyme exhibited great operational stability (retaining approximately 61% residual activity after ten consecutive reuses), demonstrating that enzyme leakage during the catalysis reaction was efficiently reduced. Furthermore, the activity of immobilized pullulanase was significantly (p < 0.01) higher than that of free pullulanase in a low pH range (pH < 3.0) and temperature over 60 °C, and the immobilized enzymes retained 45% of their initial activity after 5 h at 60 °C, compared to 21% for the free enzyme. These results indicated that immobilized pullulanase was efficient in terms of catalytic activity and can be applied to continuous starch processing applications in the food industry.

Effective fermentation monitoring is a growing need during the production of wine due to the rapid pace of change in the industry. Total reducing sugar, pH and amino acid nitrogen (AAN) are the three most important process variables indicating the status of the Chinese rice wine (CRW) fermentation process. In this study, the potential of near-infrared (NIR) spectroscopy and mid-infrared (MIR) spectroscopy as rapid tools to monitor the evolutions of these three chemical parameters involved in the CRW fermentation process was investigated and compared. The results demonstrated that compared with the partial least-squares (PLS) model based on the full spectrum, the model based on the spectra intervals selected by the synergy interval partial least-squares (SiPLS) algorithm had higher prediction accuracy. In addition, nonlinear models outperformed linear models in predicting fermentation parameters. After systemic comparison and discussion, it was found that for either models developed based on NIR spectra or models developed based on MIR spectra, SiPLS-support vector machine (SiSVM) models obtained the best result with the highest prediction precision. The overall results indicated that it was feasible to monitor the fermentation process of Chinese rice wine using NIR and MIR spectroscopy.

In this study, Fourier-transform near infrared (FT-NIR) spectroscopy in combination with chemometrics was utilized to determine the antioxidant capacity and γ-aminobutyric acid (GABA) content of Chinese rice wine (CRW). Interval partial least-squares (iPLS) and extreme learning machine (ELM) were used to improve the performances of partial least-squares (PLS) models. In total, four different calibration models, namely PLS, iPLS, ELM, and ELM models based on the subintervals selected by iPLS (iELM), were developed in this study. It was observed that the performances of models based on the efficient spectra intervals selected by iPLS were much better than those based on the full spectrum. In addition, nonlinear models were superior to linear models. After systemically comparison and discussion, it was found that for all of the four parameters determined, iELM model achieved the best result with excellent prediction precision. The coefficient of determination for the prediction set (R2 (pre)), and the residual predictive deviation for the prediction set were 0.932 and 4.07 for 1,1-diphenyl-2-picrylhydrazyl assay, 0.970 and 6.21 for 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt assay, 0.974 and 6.29 for total reducing antioxidant power assay and 0.952 and 4.75 for GABA, respectively. The overall results demonstrated that FT-NIR combined with efficient variable selection algorithm and nonlinear regression tool could be used as a rapid alternative method for the prediction of the antioxidant capacity and GABA content of Chinese rice wine.

There is a growing need for the effective fermentation monitoring during the manufacture of wine due to the rapid pace of change in the wine industry. In this study, Fourier transform near-infrared (FT-NIR) spectroscopy combined with chemometrics was applied to monitor time-related changes during Chinese rice wine (CRW) fermentation. Various wavelength selection methods and support vector machine (SVM) algorithm were used to improve the performances of partial least squares (PLS) models. In total, ten different calibration models were established. It was observed that the performances of models based on wavelength variables selected by variable selection methods were much better than those based on the full spectrum. In addition, nonlinear models outperformed linear models in prediction of fermentation parameters. After systemically comparing and discussing, it was found that for both ethanol and total acid, genetic algorithm-support vector machine (GA-SVM) models obtained the best result with excellent prediction accuracy. The correlation coefficients (R2 (pre)), root mean square error of prediction (RMSEP), and the residual predictive deviation (RPD) for the prediction set were 0.94, 3.02 g/L, and 8.7 for ethanol and 0.97, 0.10 g/L, and 6.1 for total acid, respectively. The results of this study demonstrated that FT-NIR could monitor and control CRW fermentation process rapidly and efficiently with efficient variable selection algorithms and nonlinear regression tool.

•Pullulanase was immobilized on magnetic nanoparticles prepared by in situ method.•Density of surface amino groups of support was controlled.•Magnetic nanoparticles were activated by monomer or dimmer of glutaraldehyde.•Immobilized pullulanase with good stability were obtained.Magnetic chitosan/Fe3O4 nanoparticles prepared by in situ mineralization of Fe3O4 in chitosan hydrogel were first modified by 3-aminopropyltriethoxysilane (3-APTES) and then tested for the possibility of being used as carriers for the immobilization of pullulanase. It was found that the immobilized enzyme showed high activity retention (>70%) and the affinity between enzyme and substrate was improved. However, compared to the enzyme immobilized by electrostatic adsorption (87% of its initial activity lost after 10 consecutive reuses), the enzyme immobilized by crosslinking was more stable and there was less loss of activity. The improvement of activity retention and stability was further studied from the view of surface amino concentration of nanoparticles at the function of the amount of 3-APTES added, and crosslinker concentration in the activation process. The highest activity retention (89%) and operation stability (61% residual activity after 10 consecutive reuses) were obtained under the condition of 1.6 amino groups per nm2 and 15% glutaraldehyde (v/v, dimmer of glutaraldehyde). Therefore, the magnetic chitosan/Fe3O4 nanoparticle prepared by in situ mineralization was proved to be a suitable carrier. In addition, immobilized pullulanase exhibited good resistance to metal ions and detergents.

To better understand how high-shear extrusion combined with enzymatic hydrolysis affects the rice properties and subsequent fermentation, a twin screw extruder incorporated with rice treatment with thermostable α-amylase was used for simultaneous saccharification and fermentation (SSF) of Chinese rice wine. Seven pretreatment methods for rice were compared, and their impacts on rice properties and quality indices of final wine were studied. Enzymatic extruded rice had higher water solubility index (WSI), extent of gelatinization (GE), but lower water absorption index (WAI) and viscosity than those of other treated rice due to a strong synergy of shear action and enzymatic hydrolysis on the degradation and gelatinization of starch. The modification of enzymatic autoclaved rice was smaller than that of enzymatic extruded rice mainly for the lack of mechanical shearing force. Although extrusion with smaller particle size tended to have higher susceptibility to enzyme, the effect was not dramatic. This implied that manipulating particle size had limited effect on the modification of rice properties. Correlation analysis showed that the ethanol yield (EY), fermentation efficiency (FE), amino acid (AA), and soluble solid content (SSC) of finished rice wine increased as rice properties improved by enzymatic extrusion. Overall, simultaneous high-shear extrusion and enzymatic hydrolysis can be an attractive alternative to obtain modified rice with desirable properties for manufacturing Chinese rice wine or other fermentation products.

In order to investigate the effect of thermostable α-amylase on the rice physicochemical properties, free/bound phenolics, and antioxidant capacities during extrusion, seven different gradients of enzyme concentration from 0 to 6 ‰ (db of starch) were used for both hulled and whole rice. For rice treated with the same extrusion conditions, special mechanical energy (SME) input changed slightly in the presence of fiber fraction (bran/husk), while decreased greatly with increasing α-amylase levels due to the reduced viscosity and friction between mechanical elements and materials. Huge physicochemical modifications were achieved in expansion ratio (ER), bulk density (BD), water absorption/solubility indices (WAI/WSI), and viscosity via enzymatic liquefaction. The total phenolic content (TPC) retention increased dramatically (93.06 and 86.33 % for hulled and whole rice, respectively) with increasing enzyme concentrations to 6 ‰, indicating that a milder reaction environment was created with less thermal-mechanical impact on phenolics. By linear analysis, the TPC of extruded rice hulled or not was strongly and positively related with BD (R = 0.9185 or 0.9719) and WSI (R = 0.9719 or 0.8857), whereas negatively related with SME (R = −0.9460 or −0.8906). Besides, the free/bound phenolics combined with antioxidant activities (1,1-diphenyl-2-picryl-hydrazyl (DPPH), 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and ferric reducing antioxidant power (FRAP)) were all improved significantly by the separate/synergetic addition of enzyme and bran/husk used as, respectively, the “special protective agent” and rich source of bioactive compounds. In summary, thermostable α-amylase could achieve many beneficial effects on both physicochemical properties and antioxidant activities of rice extruded with/without fiber for promoting the development of cake making, wine brewing, infant food industries, or animal husbandry.

•Pullulanase was immobilized on magnetic nanoparticles prepared by in situ method.•High activity retention was obtained via optimizing process condition.•Immobilized pullulanase with good thermal and operational stability were obtained.•Immobilized enzyme exhibited a broadened and more acidic pH profiles.A novel immobilization of pullulanase has been developed by using magnetic chitosan/Fe3O4 nanoparticles (CS-MNPs). The CS-MNPs were synthesized by in situ mineralization of Fe3O4 in chitosan hydrogel and characterized by transmission electron microscopy, vibrating sample magnetometer, Fourier transform infrared spectroscopy, thermogravimetric analyzer and X-ray diffractometer. The resultant material (CS-MNPs) was used as support for the covalent immobilization of pullulanase with glutaraldehyde as cross-linker. In the process of pullulanase immobilization, both the amount (g) of immobilized pullulanase and the activity retention(%) increased with enzyme concentration increasing (15–60 μg/ml), and the optimum activity retention (93.5%) was obtained at pH 3.5. In enzymatic properties, the immobilized enzyme exhibited a broadened pH profiles and higher thermal stability than the free enzyme. The optimum pH of immobilized pullulanase (3.5) was lower than that of the free enzyme (4.4), and the immobilized enzymes could retain about 84% of their initial activity after incubated for 5 h at 60 °C in contrast with 58% of free enzyme. Furthermore, the immobilized pullulanase retained more than 56% of its initial activity after eight consecutive reuses. These results prove that the CS-MNPs are an effective support for the immobilization of pullulanase.Download full-size image