The use of laser differential interference contrast microscopy for the characterization of starch granule ring structure

A laser differential interference contrast (DIC) microscopy protocol was developed for the visualization of starch growth rings in an optical section series. Potato and maize starches were observed with this new technique. Partial lintnerization was necessary to visualize the rings. The best image contrast was obtained using a blue laser and image deconvolution. For native starches, growth rings were evident in potato starch, but not as much as in native normal and waxy maize starches. Lintnerization enhanced the visualization of growth rings until granule integrity became compromised (by 48 h for waxy maize and by 96 h for normal maize and potato starches). Density of growth rings was not different for normal and waxy maize starches (11.3 and 12.1 rings/10 μm) but was lower for potato starch (7.5 rings/10 μm). Compared to other techniques for visualization of growth rings such as SEM and TEM, this protocol is fast and simple with minimum sample preparation and little possibility of artifacts.