Investigating starch gelatinization through Stokes vector resolved second harmonic generation microscopy

Nirmal Mazumder,Jianjun Qiu,Fu-Jen Kao,Lu Yun Xiang

doi:10.1038/srep45816

Abstract

The changes of the morphology during heating and the degree of crystallinity of dry and hydrated starch granules are investigated using second harmonic generation (SHG) based Stokes polarimetry. A spatial distribution of various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), and the degree of circular polarization (DOCP) are extracted and compared with the two dimensional second harmonic (SH) Stokes images of starch granules. The SH signal from hydrated and dry starch on heating differed significantly in DOLP and DOCP values, indicating that hydrated starch has a greater degree of ultrastructural amylopectin disorder. The detail of denaturation and the phase transition of hydrated starch demonstrate the significant influence of thermal processing.

Highlights

SHG images using various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP) and the degree of circular polarization (DOCP) from the acquired Stokes parameters[11]
We investigated the polarization states and reconstructed polarization parameters of SH light from both dry and hydrated starch in laboratory conditions
From the observation of the electron diffraction data of potato starch fragments, Oostergetel and van Bruggen[1] concluded that semi-crystalline domains form a network of left handed superhelices of diameter 18 nm and pitch 10 nm. It is consistent with previous reports identifying that amylopectin molecules in starch granules are the source of the SH signal[14,17]

Summary

Methods

The polarization-resolved SH images were obtained from potato starch in both dry (laboratory condition) and hydrated (suspended in water) condition using a Stokes-polarimeter. The starch granules were extracted from homegrown potatoes A drop of a dilute starch-water suspension was adhered to the coverslip and was placed on a round standard flexible thin heater (5 V, 10 mm inner diameter, temperature rise 100 °C, Taiwan KLC Corporation). A temperature programmer was connected to the heater and was controlled by changing the voltage from 20 to 100 °C. The heating plate was mounted upside-down in the microscope stage. The details of the temperature controller can be provided on request

Results

Discussion

Conclusion