Manipal scientists discover tools to manage nutrition better

Researchers at the Department of Biophysics, School of Life Sciences, Manipal University, and Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, have developed a stokes polarimeter based on non-linear optical microscopy (Second Harmonic Generation–SHG) to investigate starch gelatinisation.

The findings are published in Nature Publishing Group journal ‘Scientific Reports’ entitled ‘Investigating Starch Gelatinisation through Stokes Vector Resolved Second Harmonic Generation Microscopy.’

Starch breaks down under heat and is amenable for digestion. Using optical microscopy, the authors found that starch-water interaction environment was altered upon heating with diminishing signals. The fine structure of starch, organisation and arrangement is due to molecular packaging of amylose and amylopectin in a network and organised as alternating concentric 120-400 nm thick growth rings.

The hydrated starch, upon heating, alters the signal due to the micro-structural changes. These could be captured in traditional optical polarisation microscope by using large number of images rather than single image of starch granule.

“The slowly-digestible or resistant starch derived from uncooked food, whole grains, legumes, tubers and vegetables thus can be measured as an appropriate source of carbohydrates to provide as personalised nutrition to reduce risk of various conditions/diseases, including cardiovascular diseases,” Dr Nirmal Mazumder, the first author of the manuscript, said.

The work was undertaken with imaging specialist Dr Jianjun Qiu from Key Laboratory of Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, China.

Starch is made up of a large number of glucose units joined by glycosidic bond which breaks down into glucose and used as energy source in the body. It is produced during photosynthesis in plants and stored as granules. When the starch is undigested in the small intestine, it is called resistant starch which is indigestible by the enzymes of the human body. In the large intestine, it is fermented by the gut microbiota into metabolites such as short chain fatty acids, gases, organic acids and alcohols. The quality and quantity of resistant starch uptake may have several health benefits especially in disease conditions such as obesity and diabetes.