Effect Of Dynamic High Pressure Microfluidization On The Properties And Structure Of Amylose

Starch is one of the most abundant reproducible biological resources and mainly composed of amylose and amylopectin. Amylose is an important industrial raw material and has been widely used in many industries of food, medicine, textile, paper, degradable plastics and other fields. But native amylose possesses many limitations of prone to retrogradation, gelatinization difficultly, strong shear resistance, which to some extent restricts its processing and application. So we should use some methods to modify of amylose, making its performance better and application fields broader. However, dynamic high-pressure microfluidization (DHPM) technology is an effective physical modification means, which has been widely used in the modification of food macromolecules. Therefore, the amylose was modified by DHPM in this paper. The effect of DHPM on physicochemical properties, particle and molecular structure characteristics of amylose derived from maize and potato was investigated. The relationship between the different properties and the parameters of structure was also analyzed. The results provide some theoretical reference for DHPM technology application in starch modification.(1) The amylose was precipitated out from the corn starch and potato starch by1-butanol-isoamyl alcohol mixture and purified using saturated1-butanol crystallization repeatedly several times. The content of purified corn amylose and potato amylose estimated using iodine colorimetry was90.5%and85.3%, amylose-iodine complex maximum absorption wavelength of625nm and635nm, and iodine blue value of0.915and0.823, respectively, which indicates that the purity of the homemade amylose is high.(2) The effect of DHPM treatment with different pressure (80MPa,120MPa,160MPa, and200MPa) on the physicochemical properties of the amylose was investigated. The solubility, swelling power, transmittance, retrogradation, thermodynamic properties, freeze-thaw stability, pasting properties, and texture were determined with UV-visible spectrophotometer, differential scanning calorimetry, Rapid visco analyser, and texture analyzer. As the DHPM pressure increased, the solubility of corn amylose first increased and then decreased; swelling power increased slowly. The solubility and swelling power of potato amylose first increased then decreased with increasing pressure and reached the maximum in160MPa. The thermodynamic parameters (To, onset temperature; Tc, conclusion temperature; AH, enthalpy of gelatinization) of corn amylose reduced gradually but no significant change of potato amylose. The paste characteristic parameters, peak viscosity, through viscosity, final viscosity, setback value and pasting temperature of corn amylose reduced; the final viscosity and retrogradation value increases. The peak viscosity and through viscosity of potato amylose decreases, but the final viscosity and setback value increased. The transmittance of corn amylose increased but not obvious, and the potato amylose’s first increased and then decreased with increasing pressure. The corn amylose paste was easy to cause syneresis and precipitatation, and reached retrogradation stability after placed6h; DHPM treatment could inhibit its retrogradation. However, the retrogradation speed of potato amylose paste was slow and reached stability after placed18h; the influence of DHPM on its retrogradation had no significant regularity. The amylose freeze-thaw stability did not change significantly after DHPM treatment. The corn amylose gel springiness first increased and then decreased, and reached the highest at160MPa; adhesiveness increased; hardness, gumminess and chewiness changeed little. The potato amylose gel adhesiveness reduced; gel hardness, springiness, cohesiveness, gumminess and chewiness all showed a trend of first increasing and then decreasing, and reached the maximum at120MPa.(3) The structure characteristics including particle morphology, size, molecular groups, crystallinity, molecular weight, and other structures of different microfluidization pressure (80MPa,120MPa,160MPa,200MPa) treated amylose were studied using environmental scanning electron microscope (ESEM), atomic force microscope (AFM), particle size analyzer, fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, high performance gel permeation chromatography (HPGPC). Appearance observation of freeze-dried treated samples displayed as the floccule; SEM showed that the amylose granulars were destroyed and partially congregated after DHPM treatment; AFM images showed that the molecules space structure was changed and the height was reduced from3D images by200MPa treatment; X-ray diffraction spectra and FT-IR spectra showed that the granular crystalline structure was damaged and the relative crystallinity was declined gradually with the pressure increasing; the particle size first decreased and then increased as the pressure increased. The weight average molecular weight (Mw) of corn amylose and potato amylose was reduced from1.77×106g/mol and2.40×106g/mol to1.59×106g/mol and2.15×106g/mol, respectively, which indicated that DHPM treatment could result in amylose degradation.(4) Pearson correlations among various properties and structure parameters of amylose were observed. There are significant correlations among To,△H, peak viscosity, setback value, transmittance, sedimentation volume, freeze-thaw stability, hardness cohesiveness, and particle crystallinity.