Shin Lu

Correlations between the fine structure, physicochemical properties, and retrogradation of amylopectins from Taiwan rice varieties

ABSTRACT Fourteen varieties of rice from Taiwan, including five Indica, five Japonica, and four waxy cultivars, were used in this study for the examination of fine structure and physicochemical properties of amylopectin. The results indicated that the amylopectin of Indica rice had lower molecular weight, lower average degree of polymerization (DP), and lower average chain number when compared to Japonica and waxy varieties. The shortest average DP was 6 glucose units for all 14 rice varieties. The average chain lengths (CL) of amylopectin were 18–22, 15–18, and 17–20 for Indica, Japonica, and waxy rice, respectively. Indica varieties with high amylose content had amylopectin that comprised a few extra long chains (DP >100). The CL distribution profiles of amylopectins for these 14 varieties could be divided into two factions: CL 10–15 and CL 40–44. Amylopectin of the Indica rice had a relatively high blue value and λmax, implying that a high proportion existed as long branches. The amylopectin of three I...

Effects of milling on the physicochemical characteristics of waxy rice in Taiwan

ABSTRACT Three types of mills and six milling methods were employed to mill two waxy rice varieties (TCSW1, long grain; TCW70, short grain), and the physicochemical and functional properties of rice flour were examined. The results showed that dry-milling maintained a higher level of the chemical components than other milling methods. Wet-milling slightly increased solubility as test temperatures increased, and significantly increased swelling power at 75 and 85°C for TCSW1 and TCW70, respectively. Hammer and semi-dry hammer milling gave higher percentages of coarse particles (100–300 μm); cyclone and turbo milling led to a more even particle-size distribution, and the wet-milling gave the finest particles (10–30 μm). Dry hammer-milled rice had higher gelatinization and pasting temperatures, and semi-dry grinding milling resulted in the lowest pasting temperature, setback viscosity, and enthalpy value among the mills. The final quality of the two waxy rice varieties was profoundly affected by the mill typ...

Molecular Characteristics Influencing Retrogradation Kinetics of Rice Amylopectins

ABSTRACT The enthalpy changes (ΔH) for melting of crystallites formed during retrogradation of 60% (w/w) amylopectins (AP) aged at 4°C were investigated using AP from 13 rice cultivars with well-known structural properties. According to the Avrami equation, the resultant kinetic parameters for AP retrogradation were obtained in relation to structural factors. Generally, the AP systems studied showed two stages of retrogradation behavior during early (≤7 days) and late (≥7 days) storage. The Avrami exponent for early-stage kinetics (n1, 1.04–5.54) was greater than the corresponding value for late-stage kinetics (n2, 0.28–1.52). While the Avrami K constant of the early-stage kinetics (K1, 1.0×10-5 to 2.3×10-1 day-n) was lower than the corresponding value of late-stage kinetics (K2, 4.4×10-2 to 1.4 day-n). The ΔH values for late and infinite retrogradation stages showed a significantly positive correlation with the proportions of short chain (chain length [CL] ≤ 15 glucose units) and long chain (CL = 16–100 ...

Optimization of acid hydrolysis conditions for feruloylated oligosaccharides from rice bran through response surface methodolgy.

Response surface methodology (RSM) was employed to optimize the hydrolysis conditions with trifluoroacetic acid (TFA) to obtain the maximum amount of feruloylated oligosaccharides from rice bran. The TFA concentration and hydrolysis time effects on feruloylated oligosaccharides recovery are studied. The optimum hydrolysis conditions for maximizing feruloylated oligosaccharides recovery were 193 mM TFA concentration and 1.36 h of hydrolysis time. Under these conditions the corresponding acyl ferulic group quantity was 78.63 microg in 1 mL of hydrolysate. The model was experimentally verified with a satisfactory coefficient of R (2) (= 0.96). The quantity of acyl ferulic group in the feruloylated oligosaccharides, purified using Amberlite XAD-4, was 916.12 microg/g of rice bran under the optimum hydrolysis conditions. The proposed method accounted for 54.08% of the total acyl ferulic group in rice bran. The results suggest that the proposed conditions were useful in maximizing recovery of feruloylated oligosaccharides from rice bran.

Extrusion Processing of Rice-Based Breakfast Cereals Enhanced with Tocopherol from a Chinese Medical Plant

ABSTRACT Brown rice flour was mixed with a Chinese medical plant (Euryale ferox Salisb.) and processed to make ready-to-eat breakfast cereals using twin-screw extrusion. Levels of 15 and 20% feed moisture in flour, and 200 and 250 rpm screw speed were set, and the physicochemical properties and content of α-, β-, γ-, and δ-tocopherols were determined. The data showed that 15% feed moisture gave a low bulk density and water absorption index but a high expansion ratio and water solubility index. High screw speed (250 rpm) produced a result similar to that of 15% feed moisture. A sample with 85% brown rice flour with 15% E. ferox Salisb. retained the highest content of α-, β-, γ-, and δ-tocopherols (125, 6, 78, and 9 μg/g), respectively. The optimum extrusion conditions determined were 15% E. ferox Salisb. mixed with brown rice at 15% feed moisture and at 250 rpm screw speed.

Electrosynthesis of κ-Carrageenan Complexes with Gelatin

Electrosynthesis at pH 9, 12, and 11 of κ-carrageenan–gelatin complexes from electrolytes containing the components at proportions varying from 1:5 to 5:1 provided complexes in the composition varying in a range from 1:10 to 1:1.8. Components were bound mainly electrostatically, although partial insolubility of complexes in 7 M aqueous urea pointed to a part of the complexes bound covalently. None of the performed tests except solubility could confirm formation of covalent complexes. The complexation of κ-carrageenan to gelatin significantly increased the thermal stability of carrageenan, whereas the thermal stability of gelatin increased rather insignificantly.