100g of each type of rice was mixed with 200g of distilled water at room temperature. The slurries were vacuum packed using a Sammic Vacuum Sealer V410 and heated for 15h at 35ºC in a water bath. Together with the rice and water one magnetic stirring bar was placed inside each vacuum sealed bag to stir the samples during 3min at 1000rpm at room temperature. Then, the sealed bags were opened and sieved during 2min more. Each water-starch solution and sample of sieved rice was weighted separately. After that, the rice grains were washed with 50g of distilled water, stirred at 1000rpm during 2min and sieved. This process was repeated two times. The water-starch solution obtained was added to the initial solution resulting from sieving. The final solution was centrifuged for 20min at 4000 x g in relative centrifugal force (rcf) units using a Labofuge 400 Centrifuge. The supernatant was decanted and centrifuged again at 4000 x g for 20min more. The solute amount after this process was negligible. Also some filter paper was used to filter the supernatant solute but it couldn’t be collected. The pellet obtained was dried in an oven for 18h at 35ºC and during 1 more hour in a vacuum oven at 30ºC.
The dried starch was weighted to calculate the starch yield following expression:
starch yield = mass of extracted dried starch / mass of rice grains
The experiments were carried out with the help of Dr Olga Kuzmina from Prof. Welton’s Research Group.