Hui-Ming Zhou

Impact of the Soak and the Malt on the Physicochemical Properties of the Sorghum Starches

Starches were isolated from soaked and malted sorghum and studied to understand their physicochemical and functional properties. The swelling power (SP) and the water solubility index (WSI) of both starches were nearly similar at temperatures below 50 °C, but at more than 50 °C, the starch isolated from malted sorghum showed lower SP and high WSI than those isolated from raw and soaked sorghum. The pasting properties of starches determined by rapid visco-analyzer (RVA) showed that malted sorghum starch had a lower viscosity peak value (86 BU/RVU) than raw sorghum starch (454 BU/RVU). For both sorghum, X-ray diffractograms exhibited an A-type diffraction pattern, typical of cereal starches and the relative degrees of crystallinity ranged from 9.62 to 15.50%. Differential scanning calorimetry (DSC) revealed that raw sorghum starch showed an endotherm with a peak temperature (Tp) at 78.06 °C and gelatinization enthalpies of 2.83 J/g whereas five-day malted sorghum starch had a Tp at 47.22 °C and gelatinization enthalpies of 2.06 J/g. Storage modulus (G′) and loss modulus (G″) of all starch suspensions increased steeply to a maximum at 70 °C and then decreased with continuous heating. The structural analysis of malted sorghum starch showed porosity on the granule’s surface susceptible to the amylolysis. The results showed that physicochemical and functional properties of sorghum starches are influenced by soaking and malting methods.

Evaluation the quality characteristics of wheat flour and shelf-life of fresh noodles as affected by ozone treatment.

In this study, the effects of ozone treatment on the microorganism mortality in wheat flour and shelf-life of fresh noodles were investigated, as well as the physicochemical properties of wheat flour and textural qualities of cooked noodles. Results showed that the total plate count (TPC) can be largely reduced in wheat flour exposed to ozone gas for 30 min and 60 min. Whiteness of flour and noodle sheet, dough stability, and peak viscosity of wheat starch were all increased by ozone treatment. Free cysteine content in wheat flour was shown to decrease significantly (P<0.05) as the treatment time increased and remarkable protein aggregates were observed in both reduced and non-reduced SDS-PAGE patterns. In addition, ozone treated noodles were generally higher in firmness, springiness, and chewiness, while lower in adhesiveness. Microbial growth and darkening rate of fresh noodles made from ozone treated flour were delayed significantly.

Immobilization of Glucose Oxidase in Alginate-Chitosan Microcapsules

In order to improve its stability and catalytic rate in flour, the immobilization of glucose oxidase (GOX) was investigated in this work. The enzyme was encapsulated in calcium alginate-chitosan microspheres (CACM) using an emulsification-internal gelation-GOX adsorption-chitosan coating method. The interaction between alginate and chitosan was confirmed by infrared spectroscopy (IR). The resultant CACM in wet state, whose morphology was investigated by scanning electron microscopy (SEM), was spherical with a mean diameter of about 26 μm. The GOX load, encapsulation efficiency and activity of the CACM-GOX were influenced by concentration of chitosan, encapsulation time and encapsulation pH. The highest total enzymatic activity and encapsulation efficiency was achieved when the pH of the adsorption medium was near the isoelectric point (pI) of GOX, approximately pH 4.0. In addition, the molecular weight of chitosan also evidently influenced the encapsulation efficiency. Storage stabilities of GOX samples were investigated continuously over two months and the retained activity of CACM-GOX was 70.4%, markedly higher than the 7.5% of free enzyme. The results reveal the great potential of CACM-GOX as a flour improver.

Effects of High Hydrostatic Pressure on Some Functional and Nutritional Properties of Soy Protein Isolate for Infant Formula

The effects and mechanism of high hydrostatic pressure (HHP) on some functional and nutritional properties of soy protein isolate (SPI) for infant formula were investigated. Results indicated that solubility, water holding capacity, emulsification activity index, and foaming capacity were improved at lower pressure and time levels, whereas these properties declined at higher levels. However, the emulsification stability index dropped when the pressure increased and the foaming stability decreased with pressure and time levels rising. HHP-treated SPI gave better swallowing properties and in vitro digestibility than control. The hardness, adhesive force, and springiness of SPI gels increased with increaded pressure and elongated time, being lower than those of the control. Near UV circular dichroism spectra confirmed the alteration of tertiary and/or quaternary conformations caused by HHP. Sodiumdoecyl sulfate polyacrylamide gel electrophoresis results indicated that β-conglycinin was more pressure labile than glycinin, and high molecular weight subunits formed via disulfide linkage at higher treatment levels.

Delineating the protein changes in Asian noodles induced by vacuum mixing.

In this study, the effect of vacuum mixing on Asian noodle qualities was investigated based on protein components changes and gluten formation. The results showed that the proportion of salt-soluble proteins decreased in vacuum mixed noodles while alcohol and alkali soluble proteins increased. The free sulfyhydryl content decreased significantly (P<0.05) in low protein (LP) noodles while slight and not significant (P>0.05) decrease was detected in high protein (HP) samples. Remarkable protein aggregates were observed in non-reduced SDS-PAGE patterns for LP noodles. The changes in secondary structure were reflected by the increase in α-helix and β-sheet as well as the decrease in β-turns. Furthermore, vacuum mixing conferred a more continuous and compact microstructure to both HP and LP noodle sheets as well as an increased breaking force and extensibility. In addition, less deterioration in noodle structure and water migration was observed by magnetic resonance imaging (MRI) for vacuum mixed samples during storage.

The Effect of Ultrasound on the Functional Properties of Wheat Gluten

In this study, the effect of ultrasound on the foaming and emulsifying properties of wheat gluten as well as its electrophoretic and rheology properties were investigated. The foam capacity and foam stability of ultrasound treated wheat gluten proteins gradually increased as the treatment power increased, and were more pronounced at 100% power level. Excluding those of the raw wheat gluten, the lowest emulsifying capacity values and emulsifying stability were obtained with the samples ultrasound treated at 60% power level. In general, ultrasound treatment did not cause major changes on the protein electrophoretic patterns of gluten samples at the power levels used. Ultrasound affected the storage and the loss moduli with typical U-shape alteration.

Improvement of emulsifying properties of oat protein isolate-dextran conjugates by glycation.

In order to improve the emulsifying properties of oat protein, oat protein isolate (OPI)-dextran (Dex) conjugates were prepared by glycation reaction. Emulsifying properties of emulsions stabilized by native OPI (OPIN), OPI-Dex conjugates (ODC) and heated OPI (OPIH) were characterized by zeta-potential, mean droplet size and microstructure. The results showed that the covalent attachment of OPI and dextran was confirmed by determining degree of graft and SDS-PAGE. OPI-Dex conjugates were capable of forming a finer emulsion, which exhibited smaller average particle size and better storage stability under different homogenization pressures (30, 60, 90 MPa) compared with OPIN and OPIH. When assessed in different pH and ionic strength, emulsions stabilized by OPI-Dex conjugates resulted in improved emulsion stability to environmental stresses. Confocal laser scanning microscopy depicted more uniform and smaller oil droplets that had a reduced tendency to coalesce for emulsions prepared with ODC.

Functional properties of chitosan–xylose Maillard reaction products and their application to semi-dried noodle

The objective of this research was to evaluate the antimicrobial, antioxidant and darkening inhibitory activities of Maillard reaction products (MRPs) prepared from chitosan and xylose, and their effects on the preservation and quality of semi-dried noodles. The development of brown color and UV absorbance changes indicated the proceeding of Maillard reaction. The antimicrobial activity, reducing power, DPPH radical scavenging activity, copper-chelating activity and PPO inhibitory effects of chitosan-xylose conjugates increased with the reaction. Addition of MRPs could improve the textural and cooking quality of semi-dried noodles. Incorporation of 0.35% MRPs (6 h) into semi-dried noodle resulted in an extension of shelf life for more than 7 days than the control noodles (at room temperature). The discoloration caused by the addition of MRPs was limited, and MRPs could inhibit darkening of the noodle effectively. Results suggested that the MRPs could be used as a novel promising preservative for semi-dried noodles.

Heat-induced interaction between egg white protein and wheat gluten

Some wheat-based food systems, such as cakes and cookies, include mixtures of gluten and egg white protein (EWP) and are processed under heating conditions. Changes in these proteins during processing can affect the quality of the end product. This study investigated protein polymerization during heating of (mixtures of) wheat gluten and EWP. Chemical changes were studied by size-exclusion high performance liquid chromatography (SE-HPLC), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), thiol (SH) measurement and Fourier transform infrared (FTIR). During heating, protein polymerization was observed in the mixtures of gluten, glutenin, gliadin and EWP according to SE-HPLC profiles and results of SDS-extractable protein. The results of SDS-PAGE profiles of different proteins were in accordance with SE-HPLC. The number of SH groups in the majority of proteins showed a significant decrease, implying that disulfide (SS) bonds contributed to the extractability loss. In addition, changes of secondary structure tested by FTIR indicated protein aggregation.

Comparative study of four physical approaches about allergenicity of soybean protein isolate for infant formula

ABSTRACT The objective of this study was to investigate the influences of microwaving, high-intensity ultrasound (HIU), high-pressure homogenization (HPH) and high hydrostatic pressure (HHP) on the allergenicity and structural properties of soy protein isolate (SPI) for infant formula. Microwaving, HIU, HPH and HHP reduced allergenicity by 24.7%, 18.9%, 29.8% and 46.6%, respectively. Western blotting (WB) results indicated the allergens for Chinese soy-allergic childrens encompass 130 kD, 115 kD, lipoxidase, α and γ subunit of β-conglycinin, Chain A of glycinin, P34, 30 kD, 28 kD, Chain B of glycinin. SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) (with 2-ME) and WB patterns did not show significant differences among the native and modified SPIs. These four approaches influenced molecular interactions such as free sulfhydryl, hydrophobicity and zeta potential, compositions of secondary structures containing helices, strands, turns and unordered, and structural parameters including helices and strands (per 100 residues), average length of helices and strands. The epitopes of SPI allergens could be closely related to α-helix and β-sheet. In case of magnitude of secondary structure composition and parameter changes, HHP ranked top compared with other three methods. Therefore, the allergenicity reducing efficiency of HHP is much higher than those of other three treatments.