No abstract

Fine structure of sweet potato starch (SPS) and mung bean starch (MBS) by gel‐permeation chromatography (GPC) showed that the amylose in SPS and MBS had 9.0 and 1.8 chains, respectively. The long chains of amylopectin in MBS (Ap‐MB) were longer than those of amylopectin in SPS (Ap‐SP), but the short chains of Ap‐SP were shorter than those of Ap‐MB. The structures of starch noodles of sweet potato (SPSN) and mung bean (MBSN) were analyzed by GPC, scanning electron micrograph (SEM), differential scanning calorimetry (DSC), and X‐ray diffraction after hydrolysis by acid and enzymes. The results showed that the residues obtained with acid and enzymes in MBSN contained large amounts of high molecular weight fractions, and a relatively small amount of low molecular weight fractions, whereas those in SPSN contained some high molecular weight fractions and large amounts of low molecular weight fractions. SPSN exhibited higher digestibility by HCl, α‐amylase, β‐amylase, and pullulanase than MBSN. The surface of MBSN was more smooth than that of SPSN and the inside of MBSN contained long, thick, and orderly filaments, while there were many pore spaces inside SPSN from SEM. The DSC thermogram of the resistant residues from both starch noodles after acid/enzyme hydrolysis showed a broad endotherm peak near 100 °C (96 to 115 °C) due to the presence of the complexes of amylose‐lipid and lipid‐(long chains in amylopectin). Because of a lower content of branched amylose and a higher content of amylopectin in SPS, the structure of SPSN had a less distinct crystalline pattern and higher adhesiveness, whereas there was a higher content of amylose with a little branch and moderate amylopectin in MBS. Thus, the structure of MBSN had a stronger distinct crystalline pattern and good cohesiveness.

The rheological properties of starch dough are important for the production of mung bean starch noodles. In this paper, the rheological behavior of mung bean starch dough (MBSD) was measured at di#erent concentrations, temperatures, shear rates and temperature ramp. The results showed that MBSD is a thixotropic fluid, characterized by a viscosity that decreases with increasing shear rate, and increases with decreasing shear rate. However, the initial viscosity value was not restored, indicating the presence of unclosed hysteresis loops with di#erent areas in corresponding plots. The rheological behavior of MBSD could be better explained by the Cross equation than by the Power Law equation. The HerschelBulkley equation made good predictions of flow behavior of pure starch slurry. MBSD was temperaturesensitive and suitable for the Arrhenius equation. MBSD with moisture content of .. w/wῌ, starch paste content of ,. w/wῌ, shear rate of +* s ῌ+ and temperature of .*῍C exhibited a better flow performance for stirring and hanging during starch noodle production.

There is increasing interest in finding new food sources to alleviate malnutrition in developing countries. The chemicophysical, thermal characteristics and microstructure of eight typical and luxuriant broad bean varieties in China were investigated. There were significant differences (P < 0.05) among the crude protein, total starch, amylose, ash contents of cotyledon, size, color, 100‐seed weight, 100‐seed volume and seed density of the broad bean varieties. The raw flour of eight broad bean cultivars showed three distinct enthalpy peaks: (1) a broad temperature range (59.4∼81.53C) for starch gelatinization; (2) 82.97 to 105.23C for protein denaturation; and (3) 107.80–129.20C disrupture of amylose‐lipid complex. The cotyledon cell shapes of raw broad bean from eight varieties were similar and orderly when examined by Scanning Electron Micrographs, showing a regular structure in which starch granules appeared to be embedded in a protein matrix. Some proteins on the tissue surface were covered with lipid, contributing to the membrane's semitransparent appearance. PRACTICAL APPLICATIONS Broad bean is one of the important legumes in China. The Ministry of Science and Technology of China implemented a nationwide mandate to improve the productivity and enhance utilization of Chinese minor grains, including broad bean. Efforts are needed to explore new processing methods to enhance broad bean's utilization. In the present study, the properties and qualities of broad beans were investigated, namely the chemicophysical and thermal characteristics as well as the microstructure of eight typical and luxuriant broad bean varieties in China. This study may serve as the foundation to improve the quality of processed foods made from broad beans.