Preparation Of OSA Starch Nanocrystals And Their Stabilization Of Pickering Emulsions

In this study,starch nanocrystals were prepared from glutinous rice starch and pea starch with different crystal structures by high-pressure homogenization pretreatment and acid hydrolysis.Subsequently,the starch nanocrystals were modified by octenyl succinic anhydride(OSA)to enhance their hydrophobic properties.Finally,OSA modified starch nanocrystals were applied to stabilize food-grade Pickering emulsion.The main studies were as follows:As the number of high-pressure homogenization increases,the particle size of glutinous rice starch and pea starch decreases,and the surface of starch granules becomes loose.The crystallinity of the two kinds of starch decreased slightly after high pressure homogenization pretreatment,but their crystallization type did not change.The yields of glutinous rice starch nanocrystals and pea starch nanocrystals prepared by high pressure homogenization pretreatment with acid hydrolysis was slightly lower than that prepared by sulfuric acid hydrolysis,and the hydrolysis time was shortened by 1 day.According to the X-ray diffraction pattern,the two starch nanocrystals prepared were dominated by crystalline structures,and the Zeta potential results suggested that they are negatively charged,and the particle size of the two starch nanocrystals was about 200 nm determined by laser particle size analyzer.Glutinous rice starch nanocrystals and pea starch nanocrystals prepared by high pressure homogenization pretreatment and acid hydrolysis were esterified with octenyl succinic anhydride.It was confirmed that OSA starch nanocrystals with different degrees of substitution were successfully prepared by scanning electron microscope,Fourier transform infrared spectroscopy and Zeta potential measurement,and it was determined by X-ray diffractometer that OSA modification would not destroy the crystal structure of starch nanocrystals.With the increase of the amount of OSA in the esterification reaction,the contact angles of OSA glutinous rice starch nanocrystals and OSA pea starch nanocrystals increased from 40.2° and 37.8° to 56.1°and 65.0°,respectively.The results of interfacial tension and surface tension show that the hydrophobic ability of the two starch nanocrystals modified by OSA is enhanced,and they can be firmly adsorbed on the oil-water interface,enabling them to become solid particle emulsifiers for stabilizing Pickering emulsions.Using walnut oil as the oil phase,the O/W Pickering emulsion was stabilized by OSA glutinous rice starch nanocrystals and OSA pea starch nanocrystals,respectively.The observation of Pickering emulsion system by optical microscope and laser confocal microscope suggests that compared with starch nanocrystals,OSA starch nanocrystals are more effective in stabilizing Pickering emulsion,and the droplets are uniformly dispersed,low fluidity and high viscosity.In addition,with the increase of the degree of substitution of OSA,the particle size of Pickering emulsion stabilized by OSA glutinous rice starch nanocrystals and OSA pea starch nanocrystals decreased from 164.0 ?m and 55.8 ?m to 58.9 ?m and 38.9 ?m.respectively,and the emulsification index of Pickering emulsion prepared by OSA starch nanocrystals reached 0.92 after one month,indicating that the Pickering emulsion prepared from OSA starch nanocrystals has high stability.Starch nanocrystals as food emulsifiers are applied in Pickering emulsion,which has high potential for application and provides a theoretical basis for preparing stable food grade Pickering lotion.