Preliminary study of ratio of amylose and amylopectin as indicators of glycemic index and in vitro enzymatic hydrolysis of rice and wheat starches

Gowri Murugadass, Kavita Dipnaik


Background: Wheat and rice form the staple food of large majority of the population throughout the world. Starch is a carbohydrate which is a homopolymer consisting of a large number of D-glucose units joined by α- glycosidic bonds. Starch can be separated into two fractions-amylose and amylopectin. Amylose, Amylopectin ratio is an indicator of Glycemic Index. Starches with lower amylose content will have higher glycemic indexes. Invitro digestion of starch provides efficient means of analysing carbohydrate digestibility and hence glycemic properties of foods. Invitro digestion indicates how a given food item is likely to behave in vivo, in terms of rate and extent of sugar release from starch, by stimulating physiological processes occurring in the mouth, stomach and small intestine. The rate of starch hydrolysis which gives rise to sustained release of reducing sugars would be preferred by the diabetics.

Methods: In our study, starches of wheat and rice were first isolated. Amylose and Amylopectin ratio was determined to predict the glycemic index of both. Wheat and rice having the same amylose and amylopectin ratio were selected for our study. These isolated starches were subjected to invitro enzymatic hydrolysis by salivary and pancreatic amylases. Reducing sugars released after hydrolysis and incubation of 0, 5, 10, 15, 20 and 30 minutes were estimated by Folin-Wu method. Statistical analysis was carried out in the form of unpaired student’s t-test to find significant difference between means of reducing sugars release by wheat and rice during enzymatic hydrolysis.

Results: Having compared the starches of wheat and rice having the same amylose-amylopectin ratio, it was seen that the rice had low digestibility than the wheat starch. Rice starch releases less amount reducing sugars gradually while the wheat starch releases more reducing sugars rapidly in a short period of time. This can be due to amylopectin A which might be present in larger quantities in wheat starch than in rice starch which assists in rapid digestion of wheat starch.

Conclusions: Our findings revealed that rice starch released less reducing sugars gradually over a period of time while wheat starch released more reducing sugars rapidly. So, rice is the best option for diabetics for consumption because of its comparatively low release of reducing sugars as compared to wheat.


Amylase, Amylopectin, Amylose, Glycemic index, Starch

Full Text:



James B, Roy W. Starch: Chemistry and technology. Food Science and Technology International Series. Edited by Academic Press-Elsevier. 2009.

Chawla R, El-Metwally TH, Suchanda S. Textbook of Medical Biochemistry. 2nd ed. Wolters Kluwer Publications;2017.

Rafi MD. Textbook for Biochemistry for Medical students. 2nd ed. Universities Press;2014.

Kurusawa H, Kanauti Y, Yamamoto I, Hayakawa TI. Agricultural Biological Chemistry. Taylor and Francis online. 1969;33:798.

Badenhuizen NP. Methods in Carbohydrate Chemistry. by RL Whistler, Academic Press Inc., New York, NY. 1964:14.

McCready RM, Hassid WZ. The separation and quantitative estimation of amylose and amylopectin in potato starch. J Am Chem Soci. 1943;65(6):1154-7.

Folin O, Berglund H. A colorimetric method for the determination of sugars in normal human urine. J Bio Chem. 1922 Mar 1;51(1):209-11.

Khanal AB. Mahajan's methods in biostatistics for medical students and research workers. 8th Edition, Jaypee Brothers Medical Publishers (P) Ltd;2016.

G Chen GX, Zhou JW, Liu YL, Lu XB, Han CX, Zhang WY, et al. Biosynthesis and regulation of wheat amylose and amylopectin from proteomic and phosphoproteomic characterization of granule-binding proteins. Scientific reports. 2016;6:33111.

Wani AA, Singh P, Shah MA, Schweiggert‐Weisz U, Gul K, Wani IA. Rice starch diversity: Effects on structural, morphological, thermal, and physicochemical properties-a review. Comprehensive Rev Food Sci Food Safety. 2012 Sep;11(5):417-36.

Behall KM, Scholfield DJ, Yuhaniak I, Canary J. Studies on Diets containing high amylose vs amylopectin starch: effects on metabolic variables in human subjects. Am J Clin Nutr. 1989;49(2):337-44.

Davis W. Wheat belly: lose the wheat, lose the weight, and find your path back to health. Rodale Books; 2014 Jun 3.