•Establishing the rejection sequence spectrum of six commercial available monosaccharides.•The differences of Robs were mainly due to the differences of molecular structures.•A novel method was used to characterize the effective sizes of monosaccharides molecules.•The Donnan steric pore model was used to calculate Rcal by the computational molecular size.•Concentration polarization was taken into account to calculate Rreal and the Rcal agreed well with Rreal.To evaluate the feasibility of mixed monosaccharide separation by nanofiltration (NF), a commercial membrane, Desal-5 DK1812, was selected to filter six monosaccharides, including glucose, fructose, mannose, sorbose, arabinose, and xylose. The experiments were performed under the same conditions in single batch of full cycle mode, and the sequence of monosaccharide nanofiltration rejections was obtained. Differences in NF rejections (Robs) were analyzed by comparing the molecular structures of the monosaccharides, after which computational molecular sizes (rs) were calculated by a mathematical formula correlated with the 3D structures of the molecules. The Donnan steric pore model was used to obtain the rejections (Rcal) of the monosaccharides as a function of rs. Concentration polarization was also taken into account to calculate Rreal. The results showed that the rs values of fructose, glucose, mannose, sorbose, arabinose, and xylose were 0.3235, 0.3156, 0.3113, 0.3012, 0.2748, and 0.2677 nm, respectively, and that their Rcal agreed well with their Rreal. Therefore, differences in Robs were mainly due to differences in the molecular structures of the monosaccharides, and calculating rs using molecular structural parameters is reasonable. The results indicated the extreme importance of amplifying rejection differences by regulating computational molecular sizes when separating mixed monosaccharides by NF.

The potential interactions between milk proteins (whey proteins and caseins) and γ-aminobutyric acid (GABA), alone and in combination, and the physiochemical properties of GABA-fortified milk were investigated in the present study. After mixing 0.05–1.0% (w/w, based on the solution) GABA with 0.6% (w/v) whey proteins and with 2.6% (w/v) caseins, sequential preheating (60 °C), homogenization (20 MPa), and pasteurization (72 °C for 15 s and 138 °C for 2 s) processes were used to simulate practical processing conditions for GABA-fortified milk production. GABA mainly cross-linked β-lactoglobulin (but had no remarkable cross-linking effect on caseins), adducted with α-lactalbumin and αs1-casein fractions (not excluding other fractions in whey proteins/caseins) via the amide linkage under the sequential processing conditions, which was confirmed by electrophoresis, mass spectroscopy, and amino acid composition analysis. Characterization of the physiochemical properties (protein solubility, relative surface hydrophobicity, ζ-potential, particle size, and fluorescence intensity) of the GABA-fortified protein solutions substantiated the presence of the cross-links and adduction reactions. In addition, GABA tended to form its dimer, trimer (line-like structure) and 3–8 membered ring structure oligomers. The interaction between GABA and whey proteins/caseins provides insight into the evaluation of the food quality and chemical safety (due to protein/GABA derivatives) of GABA-fortified milk.

Characterization of physical properties of fruits represents the first vital step to ensure optimal performance of fruit processing operations and is also a prerequisite in the development of new processing equipment. In this study, physical properties of engineering significance to processing of three popular cultivars of clingstone peaches were evaluated, including dimensional parameters, mass, dimensional ratios, aspect ratio, elongation index, sphericity, bulk density, texture, color, and flavor. Based on these physical properties, multivariate analysis of variance (MANOVA), canonical variate analysis (CVA), principal component analysis (PCA), and partial least squares and linear discriminate analysis (PLS-LDA) were applied to qualitatively and quantitatively discriminate the cultivar difference. Results showed that the studied peach cultivars had significantly different (p < 0.05) geometric characteristics. The peaches can be classified based on the cheek diameter (Dc) into three different size categories, including small- (Dc less than 60 mm), medium- (Dc between 60 mm and 70 mm), and large- (Dc higher than 70 mm) sized peaches. The peach flesh firmness significantly (p < 0.05) decreased with the increase of peach size, while the pit dimensions were independent of peach size. There were no apparent distinctions in color characteristics, bulk density, and sugar content among the three cultivars. The measurements and quantitative discrimination of peach properties in this study would benefit equipment design and process innovation to enhance the processing efficiency and quality of processed peaches.

Zijuan tea is a new cultivar produced in Yunnan province of China. Unlike most tea cultivars, Zijuan tea is anthocyanin-rich. The composition and antioxidant activities of anthocyanins of Zijuan tea were studied for the first time in this paper. Anthocyanins were extracted with acidified methanol and quantified as 707 ± 28 μg/g of dry weight (cyanidin-3-O-β-d-glucoside equivalent) by high-performance liquid chromatography (HPLC) analysis. Four anthocyanins were successfully identified after Amberlite XAD-7HP adsorption column chromatography and octadecyl silane (ODS) flash chromatography. Among the four, delphinidin-3-O-β-d-galactoside (1) and cyanidin-3-O-β-d-galactoside (2) were confirmed by liquid chromatography–electrospray ionization mass spectrometry (LC-ESI-MS) and HPLC. Delphinidin-3-O-β-d-(6-(E)-p-coumaroyl) galactopyranoside (3) and cyanidin-3-O-β-d-(6-(E)-p-coumaroyl) galactopyranoside (4) were characterized by the high-resolution time-of-flight-mass spectrometry (HRTOF-MS) and nuclear magnetic resonance (NMR) spectrometry. The antioxidant activities of compounds 3 and 4, which composed approximately 75% of the total anthocyanins content in HPLC analysis, were evaluated by DPPH and FRAP assays. Results showed that both had higher antioxidant activities than commercial antioxidants butylated hydroxytoluene (BHT) used as one of controls in these assays.

•A model was built to predict total retention in multi-components solution during diafiltration.•A simplified binary system with membranes of different pore size was well verified the model.•Commercial multi-component solution, soybean molasses, was well employed to verify the theory.•The increment of total retentions was observed, and was testified by the model.•The retention curve predicted by the model agreed well with the experimental data.To investigate the membrane separation performance of multi-components solution throughout continuous volumetric diafiltration (CVD), sucrose and glucose were implemented as model solute. Two commercial nanofiltration (NF) membranes (QY-NF-1-SW with molecular weight cut-off [MWCO] of 150 Da and QY-NF-3-D with MWCO of 250 Da) were operated in batch recycling mode. Flux (Jv), trans-membrane pressure (ΔP), concentrations in feed (Cf) and permeate (Cp) were collected, and the retentions (R) were calculated. Based on the Spiegler and Kedem (S–K) equation, a theoretical R model was established. The model was employed to establish the mass balance equations in a feed tank during CVD. A novel revised retention equation was established to simulate CVD of sucrose and glucose mixture solution. Further, the model was popularly applied in ultrafiltration (UF) of the multi-components solution-soybean molasses by a commercial membrane (QY-UF-1-G with MWCO of 1 kDa). It was predicted in theory the total retention of multi-components increased, since the concentration of low retention solute declined with diafiltration process time when the flux was insignificantly changed which was then demonstrated by the experiment. The results showed that the retention curve predicted by the model agreed well with the experiment, and the revised retention equation was well designed for industrial food fluids.