Effect of addition of enzymatically modified guar gum on glycemic index of selected Indian traditional foods (idli, chapatti)

- Guar gum (GG) was modified by solid state enzymatic modification with mannanase.
- Modified guar gum (MGG) had lower viscosity and water absorption index than GG.
- MGG reduced idli batter viscosity and chapatti dough stickiness compared to GG.
- MGG added at 5% reduced GI of idli from 71.28 to 61.63.
- MGG added at 5% reduced GI of chapatti from 62.56 to 53.45.

India has a high prevalence of type 2 diabetes and there is a need to develop low glycemic index (GI) foods or modify existing popular foods to lower their GI. Guar gum, a hydrocolloid and soluble fibre, may be used as an additive for lowering glycemic response of foods. It increases the viscosity of food systems and may adversely affect their processing and physical properties, posing a constraint on the concentration at which it can be used in foods. In this study solid state enzymatic modification with mannanase was carried out to improve viscous properties of guar gum, facilitating the use of a higher concentration of the gum to lower GI of two popular Indian traditional foods, idli and chapatti. The modification process was optimized; 40 µl mannanase/g guar gum was used and the reaction was carried out at pH 5, temperature of 50 °C for a period of 48 h. Incorporation of the modified guar gum at 5% resulted in lower idli batter viscosity (Δviscosity: 33,538 cps), higher bulk density of idli (Δbulk density: 0.013 g/cc) and lower stickiness of chapatti dough (Δstickiness: 6.76 g) as compared to idli and chapatti with added unmodified guar gum. Texture and sensory attributes of both the products with 5% modified guar gum were found to be acceptable. GI of idli was reduced from 71.28 to 60.00 and 61.63 and GI of chapatti was reduced from 62.56 to 51.25 and 53.45 by addition (5%) of unmodified and modified guar gum respectively.

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