Designing bread for GI control
20 Aug 2015 NUS food scientists have reported that bread structure affected human chewing behavior which may explain the lower glycemic index (GI) of steamed bread.
Three types of bread, i.e. baked bread, steamed bread and baguette, prepared from the same formulation but using different processing conditions, showed significantly different structural and physical characteristics. Such differences led to different levels of chewing effort and structure disintegration required to swallow the bread boluses. Baguette, with the dry and hard crust, required a significant greater chewing effort and was extensively broken down with more saliva impregnated compared to the steamed bread. By removing the crust and skin from the bread samples, all three types of bread crumb were breakdown into similar level during mastication. A strong correlation was found among bread structure, texture and oral processing behavior.
A team led by Prof ZHOU Weibiao from the Food Science & Technology Programme in the Department of Chemistry, NUS and Prof Jeya HENRY (A*STAR Singapore Institute of Clinical Sciences) has demonstrated the possibility to produce bread with various structures and textures by only varying the processing conditions. Different from the reformulation bread with low GI ingredients to reduce its GI, this study aims to understand how bread structure will affect its digestibility and glycemic loading (see Figure). Results of the oral processing study shed some light on the reason why steamed bread had a reduced glycemic response as compared to baked bread, which was reported in the team’s earlier study on in vivo digestion of bread. Two important factors, the grain feature of bread crumb and physical properties and relative portion of baked curst or steamed skin, should be considered in designing bread with prescribed oral processing level and digestibility. The research was conducted by PhD candidate Ms GAO Jing and Hons graduate Ms Jocelyn WONG.
Three types of bread with the same formulation was prepared by varying the processing conditions. Distinctly different structure and texture were obtained. Oral processing of baguette and baked bread dry and thick crust required greater chewing effort and results in smaller particles and more saliva in the swallowable bolus. The difference in the bolus structure might partially explained the difference between the GI of baked and steamed bread as observed in our previous study. [Image credit: GAO Jing]
Gao J, Wong JX, Lim JCS, Henry J, Zhou W. “Influence of bread structure on human oral processing. Journal of Food Engineering”. (2015) Article in press