Faxing Luo

Ionic liquids as solvents for dissolution of corn starch and homogeneous synthesis of fatty-acid starch esters without catalysts

Ionic liquids (ILs) utilized for dispersing cellulose have gained increasing attention in recent years, but the number of the reports using ILs for starch is still limited. In this study, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and 1-ethyl-3-methlyimidazolium acetate ([EMIM]AC) were used to dispersing corn starch. Dimethyl sulfoxide (DMSO), a traditional organic solvent for starch, was added into [BMIM]Cl, and the mixture of [BMIM]Cl/DMSO was utilized for dispersing corn starch as well. Results showed that the starch granules dispersed in ILs was much smaller than native starch granules, and large starch aggregates were partially formed. Starch granules dispersed in [BMIM]Cl at 100 °C for 60 min remained less crystallinity than native starch granules, while it was disappeared when starch granules were dispersed in [EMIM]AC at 100 °C for 60 min. Homogenous synthesis of fatty-acid starch esters without catalysts in these ILs was also studied. The degree of substitution (DS) value of starch laurate was reached to 0.053, 0.068 and 0.100 in [BMIM]Cl, [EMIM]AC and the mixture of [BMIM]Cl/DMSO, respectively, at the reaction conditions of lauric acid/AGU molar ratio 1:5, temperature 120 °C at a reaction time of 3 h.

Distribution of octenylsuccinic substituents in modified A and B polymorph starch granules.

The octenylsuccinic (OS) substituent distribution in octenylsuccinic anhydride (OSA)-modified normal maize and potato starches with different degrees of subsititution (DS) was studied using confocal laser scanning microscopy (CLSM) and surface gelatinization. The remaining non-gelatinized portions of starch granules after removal of surface-gelatinized starch (remaining granules) were studied with light microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and the level of succinylation. Results showed that greater proportions of the OS groups were present at the periphery than at the core of the granules. However, the granular interior of OS maize starch has higher fluorescent intensity than that of OS potato starch, as shown by CLSM. The DS of OS maize starch degraded less than that of OS potato starch under the same degree of gelatinization. In addition, the characteristic peaks of the remaining OS maize granules in the FTIR were more protruding than that of the OS potato granules after 50% chemical surface gelatinization. The results implied that maize starch displayed much more homogeneous OSA reaction pattern when compared to potato starch. With the special architectures (pinholes and channels) of maize, it is easier to change the location of OS groups than with potato starch by changing reaction conditions or starch pretreatments.

The mechanism of starch granule reacted with OSA by phase transition catalyst in aqueous medium.

The reactivity of octenyl succinic anhydride (OSA) with starch by phase transition catalyst (PTC) was investigated. The effects of two types (quaternary ammonium salt and non-ionic surfactant) and concentrations of PTC on the degree of substitution (DS) and reaction efficiency (RE) of OS-starch were examined. In aqueous medium, the use of a PTC, polyoxyethylene lauryl ether (AEO) produced derivatives with higher DS than others. The DS of OS-starch reached 0.0195 with 0.1% AEO, significantly higher than that (0.0182) without the use of PTC. As the concentration of AEO increased, the DS of OS-starch did not increase. The structural of AEO was investigated by nuclear magnetic resonance (NMR) spectroscopy. Conductivity measurement and Fourier transform infrared (FT-IR) spectroscopy confirmed that AEO could form complexes with Na(+). The complex of AEO and Na(+) could combine with starch-O(-), it should be possible to improve the transport of anion starch-O(-) to the hydrophobic reagents.