Yu-guang Zhou

The effect of partial gelatinization of corn starch on its retrogradation

The objective of this work was to investigate the effect of partial gelatinization of starch on its retrogradation using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The Avrami equation was used to predict the evolution of starch retrogradation kinetics. The degree of retrogradation in starch samples partially gelatinized 64°C (S64), 68°C (S68) and 70°C (S70) and control (S25) increased with storage time. The retrogradation enthalpies of S68 and S70 were almost four times as high as that of S64. The S25 and S64 had dominant A-type crystalline pattern while S68 and S70 showed dominant B-type crystalline pattern. The growth of remainder crystals was faster in S25 and S64, while both the nucleation and growth rates of new crystals were faster in S68 and S70. The Avrami model was found to represent the retrogradation kinetics data of these partially gelatinized starch samples quite satisfactorily (R(2)>0.95).

Influences of Microemulsion Cross-linking Reaction and Ball-milling on Particle Size Characteristics of Potato and Maize Starches

In this study, microemulsion cross-linking treatment was used on food grade potato and maize starches for preparing micro starch particles. Laser diffraction technique was introduced to measure the particle size characteristics, including the median particle diameter (d 50), surface area mean diameter D [3, 2], volume mean diameter D [4, 3] and specific surface area of micro potato and maize starch particles. The volume distributions and number distributions were also analyzed using Mastersizer 2000 Software. The d 50, D [3, 2], D [4, 3] of the potato starch granules were reduced significantly (p < 0.05) after the microemulsion cross-linking reaction and ball-milling treatment. However, the microemulsion cross-linking treatment did not produce significant changes in the particle size characteristics of the maize starch samples.

Removal of Flaxseed Mucilage by Extrusion and Enzyme Treatments

Mixture of flaxseed meal and corn flour (90/10, w/w) was extruded at a feeding rate of 33.1kg h-1 and different die temperatures (80-160 oC), screw speeds (300-900 rpm), and initial moisture contents(18.8-35.1%) on a co-rotating twin-screw extruder. Extrudates with the maximum removal rate of mucilage of 60.3% and lesser bulk density of 0.647 g cm-3 were obtained at screw speed of 500rpm, temperature of 140°C and initial moisture content of 25.1%. The micrographs of the extrudates showed that the greater structure dispersal occurred at higher temperature and lower initial moisture content. Mucilage extracts of enzyme-treated extrudates contained less viscosity than that of unextruded meals. The solubilization of mucilage increased with the increase in soaking time. 82.3% of the removal rate of mucilage was obtained after treatment with Pectinex Smash XXL at enzymatic loading of 200µl kg-1 for 6 h.

Temperature-oriented pyrolysis on the decomposition characteristics of Chlorella pyrenoidosa.

Abstract Chlorella pyrenoidosa is one of the best candidates for biofuel production. The yield and chemical composition of decomposed products of Chlorella pyrenoidosa were determined using thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), and pyrolysis-gas chromatographic mass spectrometry (Py-GC/MS) by varying the temperature ranges. The results indicated that the main decomposition temperature of Chlorella pyrenoidosa was 294.53°C and up to 46.7% of the mass was lost. A complete decomposition of Chlorella pyrenoidosa was detected until 642.64°C. The pyrolysis of Chlorella pyrenoidosa at 800°C produced 63.58% (the maximum yield) of pyrolysis products compared to 40.22% at 300°C. It is suggested that the generation of pollutants during microalgae pyrolysis can be avoided by controlling the temperature at a relatively low stage (approximately 300°C).

Characterization of pyrolysis products obtained from Desmodesmus sp. cultivated in anaerobic digested effluents (DADE).

Abstract The present study includes the compositional analysis and pyrolysis products obtained from Desmodesmus sp. cultivated in anaerobic digested effluents (DADE) from 300°C to 800°C. Compared to Desmodesmus sp. cultivated in BG11 (DBG11), both species exhibited a hydrogen content of ca. 6%, ca. 7% of nitrogen, and ca. 0.56% of sulfur except carbon content, of which was lower than DBG11. Pyrolysis products of DADE consisted of aliphatic hydrocarbons, aromatic hydrocarbons, acids, nitrogen compounds, phenols, polycyclic aromatic hydrocarbons (PAHs), alcohols, aldehydes, and furans. Pyrolysis of DADE at 800°C produced 62.52% (the maximum yield) of pyrolysis products compared to 41.89% at 600°C. Considering the reasonably high yield and minimum release of pollutants, lower temperature (600°C) was found to be optimum for producing biofuel from DADE. A process combing anaerobic digestion and algae cultivation can be proposed as a direct and effective way to produce biofuel so as to reduce contaminations to the environment.

Effect of Flaxseed Meal Addition on Dynamic Mechanical Properties of Rice Starch Films

Starch-based films have promising application on food packaging due to their outstanding performance with flexibility and transparency. On the other hand, the mechanical properties of starch films should be improved. The aim of this work is to enhance the mechanical performance of starch films by reinforcing the films with flaxseed meal (flaxseed fiber and protein). Films were prepared by casting technique, from film-forming suspensions of rice starch, flaxseed meal, glycerol and water. The dynamic mechanical method was used for measurement of the starch film samples. Films reinforced with flaxseed meal showed higher tensile strength, lower deformation capacity and higher the glass transition temperature (Tg) than films without flaxseed meal.

Effect of Different Heating Processes on the Dynamic Mechanical Properties of Potato Slice

The study was carried out in order to determine the dynamic mechanical properties during heating by means of dynamic mechanical analyzer (DMA). Potato slice in the shape of rectangular was obtained with scalpel. The samples were heated from 35°C up to 115°C at different heating rates (5°C/min and 10°C/min) and different modes (creep mode and controlled force mode) on three-point bending clamp. Its different strain changes were recorded. The potato slice was wrapped with aluminum foil to prevent unnecessary weight loss during heating. The strain changed gradually along with time and stress. Differential scanning calorimetry was also conducted from -60°C to 120°C at 5°C/min and 10°C/min. Ice melting and starch gelatinization endotherm appeared a shifting trend to lower temperature.