Abstract
The changes in the structures of corn endosperms immersed in different reagents were studied, in order to preliminarily determine the mode of binding of starch and protein in the endosperm. The corn endosperm was immersed in Sulfurous acid, NaOH, ethanol, L-cysteine and morel berry, respectively. The dissociated starch content was analyzed using water as the reference. The results of the treatment were analyzed by the dissociated starch content, optical microscopy and scanning electron microscopy. The test results showed that by immersing in NaOH solution, the protein matrix was effectively decomposed, the protein in the endosperm was dissolved and the highest amount of starch granules were released. Sulfurous acid and L-cysteine solution could make the protein matrix into pieces by destroying intermolecular disulfide bridge and the starch granules would be released. There were some holes on the surface of starch granules after L-cysteine steeping. Immersed in the morel berry, there were holes on the protein matrix surface and the water absorption of corn endosperm was improved. In case of the sample immersed in ethanol, the zein was dissolved, whereas the matrix protein was still intact with the starch grains that still bound to it. By analysis of the microscopic structure and morphological change of starch and protein in corn endospers in different comsteep liquor, it is demonstrated that the main reason which the starch grains were tightly wrapped by Glutenin is the intermolecular disulfide bonds in glutelin. In addition, a part of the protein combined with starch granules directly. The study provided a reference for exploring the structure of binding of starch and protein and their interaction in corn.
Highlights
Corn is an important food and feed resources for human beings and an important raw material for producing starch
Results of optical microscopy study of corn cutin endosperm immersed in different liquids: After the treated corn samples were immersed in different reagents for 36 h, slices in the region of the cutin endosperm were prepared and the changes in the structures of starch and protein were observed under an 100X oil mirror optical microscope, in order to obtain the images of cutin region (Fig. 1)
The reticular structure almost disappeared, as most of the proteins were decomposed into pieces and a large number of starch grains were dissociated
Summary
Corn is an important food and feed resources for human beings and an important raw material for producing starch. The starch content in corn is approximately 70% and it is present in the form of starch grains in corn endosperm (Ji et al, 2003). About one third of the starch material is used as food, in medicines and beverages. Another one thirds is used in paper-making, packaging, in textiles and for petroleum products across the world (Jinlan, 2005). Corn starch plays an important role in the deeping processing of whole corn grains. The ordinary, super sweet and waxy corn starch grains were spherical-shaped. There were a few sunken starch grains in the ordinary corn and the size of the waxy corn starch grains was uniform with a large number of sunken starch grains
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