| This paper was mainly related on the preparation of octenyl succinic anhydride (OSA) starches from the isolated early indica rice starch in aqueous slurry systems. The physicochemical properties of octenyl succinic anhydride modified starches with different viscosities have also been investigated.First, it studied the production process of early indica rice starch with using response surface methodology. The suitable parameters for the extraction of starch from early indica rice were selected as follows: extraction period 11.5h, extraction temperature 35℃, concentration of NaOH slurry 0.52% (in proportion to water, w/w), ratio of rice flour to water 1:2.5 (w/v, kg/L). The residual protein content was 0.13±0.03% and the yield of starch was 66.7%.Seven early indica rice starches with different amylose contents (AC) were modified by OSA in aqueous suspension systems to evaluate the effect of AC on starch esterification. The results indicated that the AC had a positive impact on the OSA modification. As the AC increased from 0% to 39.6%, the degree of substitution (DS) increased from 0.024 to 0.030 and the reaction efficiency (RE) increased from 62.8% to 77.5%. X-ray diffraction scans confirmed that the amylose was mainly present in amorphous domain of the granule and was highly substituted after the OSA treatment. The RVA profiles demonstrated that the OSA starches had higher viscosities than their native counterparts. Moreover, negative correlations were observed between the AC and the major RVA parameters (e.g., peak viscosity, hot paste viscosity, cool paste viscosity and breakdown viscosity).Considering the viscosity and AC, Jiazao312 was selected as the material. The OSA esterification was optimized in aqueous slurry systems by means of response surface methodology. The results indicated that the suitable parameters for the preparation of OSA starch from early indica rice starch were selected as follows: reaction period 4h, reaction temperature 33.4℃, pH of reaction system 8.4, concentration of starch slurry 36.8% (in proportion to water, w/w), amount of OSA 3% (in proportion to starch, w/w). The DS was 0.0189±0.0003, and the RE was 81.5±1.3%.The structures of the OSA modified starches were studied with modern instruments. FT-IR spectroscopy showed characteristic absorption of the ester carbonyl groups in the OSA starch were detected at 1724cm-1. A peak at 1572 cm-1 occurred, which is ascribed to the asymmetric stretching vibration of carboxylate RCOO-. SEM and X-ray diffraction revealed that OSA groups acted by first attacking the surface and some pores formed, but OSA modification caused no change in the crystalline pattern of rice starch up to DS 0.046.Moreover, the pasting properties of OSA modified starches were investigated. The results showed that with increasing OSA modification, the starch derivatives had higher viscosities and paste clarity, decreased retrogradation and better freeze-thaw stability. The peak viscosities of the starches increased from 142.6 RVU to 298.0 RVU with the increase of DS from 0 to 0.018. In contrast, the peak time (time required to peak viscosity) decreased from 5.3min to 5.1min. The T% increased from 12.2% to 35.2%; the water separated from the starch paste decreased from 16.0mL to 0.8mL when storage at room temperature (25℃) for 720h; during the fourth freeze-thaw cycle, the native rice starch gels had a spongy-like texture and exuded 54.4% water, while the gels from OSA starches were soft and elastic, and discharged only 4.2% water. The paste clarity, retrogradation and freeze-thaw stability of OSA starches greatly decreased by the presence of sodium chloride, but only increased slightly in the presence of sucrose.The molecular weight of starch can be lowered to the desirable range by controlling HCl concentration and hydrolysis duration, thus producing OSA starches with different viscosities, higher paste clarity and better freeze-thaw stability than their parent counterparts, which can meet different industrial applications.The paste properties of SSOS modified from waxy maize starch, early indica rice starch, wheat starch, and potato starch were studied. RVA results indicated that the starch derivatives gelatinized at shorter time to achieve higher viscosities with increased OSA modification. After OSA modification, the paste clarity of waxy maize starch, early indica rice starch and wheat starch increased, but that of potato starch decreased. The retrogradation of several starches all dereased with the increase of DS.The digestibility of waxy maize starch, early indica rice starch, and potato starche before and after OSA modification were also studied using an in vitro method. The results revealed that the esterification of starch with OSA could impair the extent of hydrolysis by porcine pancreatic a-amylase, moreover, the digestibility decreased with the increase of DS. The digestibility of several starches: potato starch > waxy maize starch > early indica rice starch; potato SSOS > waxy maize SSOS > early indica rice SSOS. The reason need further study.
|
PDF Full Text Request