Impact of Heat Treatment on the Glycemic Index of Whole Wheat Bread

Abstract

Aim: In Turkey, bread is a major source of carbohydrates and energy. Whole wheat bread is recommended based on the evidence of its effects on prevention and treatment of obesity, diabetes and heart diseases. In our knowledge, there is not any study demonstrating the effect of heating methods on glycemic index of whole wheat bread. The aim of this study was to determine the effect of heating on the glycemic index of whole wheat bread.

Subjects and Methods: All subjects consumed 50 g digestable carbohydrate from glucose, white bread (reference food), whole wheat bread, whole wheat bread toasted in oven for 6 minutes at 220oC (test foods) after 8 hours of fasting in weekly intervals. Capillary blood glucose measurements of the subjects were made on 0, 15, 30, 45, 60, 90, and 120th minutes.

Result: Compared to glucose, glycemic index values were 78.4 for whole wheat bread; 107.7 for toasted whole wheat bread. While there was no significant difference between blood glucose levels in whole wheat bread and toasted whole wheat bread at 0., 15., 30., 60. and 90th minutes (p>0.05), statistically significant differences in 45th and 120th minutes were determined (p<0.05).

Conclusion: According to the results of the study, heat treatment of whole wheat bread for 6 minutes at 220oC raises glycemic index. Since the glycemic indexes of foods are associated with the risk of obesity and chronic diseases, cooking methods that increases glycemic index should be avoided.