Physicochemical properties of pectin-Fe(III) gained by HG-type hawthorn with different esterification degree.

In this study, the complexation ability of HG-type hawthorn pectin with trivalent iron ions after de-esterification was investigated. The moderate esterification reaction could significantly increase the iron content in HG-type hawthorn pectin. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) experiments proved that -OH and -COOH in the pectin acted as a bridge connecting Fe3+ leading to the formation of ß-FeOOH structure, and the trivalent iron ions were successfully complexed into the HG-type hawthorn pectin. In addition, infrared and ultraviolet spectroscopic scans, particle size, and potentiometric measurements were carried out to demonstrate the complexation coordination mechanism of hawthorn pectin with Fe3+, and there were differences in the complexation effect of HG-type hawthorn pectin with different degrees of esterification. The gelling properties of HG-type hawthorn pectin were subsequently verified by in vitro gastrointestinal tract simulation experiments to aid the smooth passage of ferric ions through the gastric juices and reduce irritation. The success of the experiments demonstrated that HG-type hawthorn pectin is an excellent raw material for metal complexation, and the degree of esterification is one of the important factors affecting its complexation effect, which proves its potential application value as an iron supplement.

Extraction methods and compositions of polyphenols in Shanxi aged vinegar.

The extraction, purification, qualification, and quantification of polyphenols (PPs) in vinegar are challenging owing to the complex matrix of vinegar and the specific physicochemical and structural properties of PPs. This study aimed to develop a simple, efficient, low-cost method for enriching and purifying vinegar PPs. The enrichment and purification effects of five solid phase extraction (SPE) columns and five macroporous adsorption resins (MARs) for PPs were compared. The results show that SPE columns were more effective in purifying vinegar PPs than MARs. Among them, the Strata-XA column showed a higher recovery (78.469 ± 0.949%), yield (80.808 ± 2.146%), and purity (86.629 ± 0.978%) than other columns. In total, 48 PPs were identified and quantified using SPE and gas chromatography-mass spectrometry from the SPE column extracts; phenolic acids, such as 4-hydroxyphenyllactic acid, vanillic acid, 4-hydroxycinnamic acid, 4-hydroxybenzoic acid, protocatechuic acid, and 3-(4-Hydroxy-3-methoxyphenyl) propionic acid, occupy a major position in SAV. Furthermore, considering the potential applications of PPs, the concentrates were characterized based on their bioactive properties. They exhibited high total PP, flavonoid, and melanoidin contents and excellent anti-glycosylation and antioxidant activities. These results indicate that the established methodology is a high-efficiency, rapid-extraction, and environment-friendly method for separating and purifying PPs, with broad application prospects in the food, chemical, and cosmetic industries.

The effect of ultrasound on the properties and conformation of glucoamylase.

In this study, the effects of ultrasonic treatment on the enzyme activity of glucoamylase were investigated and the mechanism of the effect was explored by determining their conformational changes. The enzyme activity was increased by 21.07% over the control with ultrasound at 420W for 10min at 60°C, and Vmax and Km values of glucoamylase were also increased. After ultrasonic treatment at 420W, thermodynamic experiments of glucoamylase showed that Ea, ΔG, ΔH decreased but slight increase in ΔS was observed. In addition, after the treatment, the UV spectra showed that the number of tryptophan and tyrosine on glucoamylase surface increased, and the contents of α-helix and random coil increased by 17.8%, 12.41%, respectively, through the circular dichroism spectrum scanning. Besides, fluorescence spectra indicated that the absorption of tryptophan has a red shift. Furthermore, fourier transform infrared spectra suggested that the glucoamylase was significantly influenced by ultrasound. The results indicated that the activity of glucoamylase could be modified by ultrasonic treatment mainly in terms of the variation of their conformation.