Yaseen Galali

Abstract

Abstract: The interest for functional foods rich in dietary fibre (DF) and low in glycaemic response (GR) is steadily increasing. This is because DF could reduce GR of food products and protect and restrict diet-associated diseases which have become common in society. But DF rich products are not always high in quality and palatability. Therefore, more fibre-rich functional products need to be designed and developed with good quality, palatability and longer shelf life. A response surface methodology (RSM) was used to develop both pita and Tandoori breads rich in DF with good quality, palatability and longer shelf life. So, a wide range of three different functional ingredients (FI) (inulin (IN) up to 8%, Guar gum (GG) up to 2% and waxy wheat flour (WWF) up to 15%) alone and in combination was selected, to investigate their influences on the cooking properties, bread quality, sensory characteristics, shelf life and GR. The results showed that the FI affected cooking properties differently. IN and WWF reduced almost all the viscosity parameters. In contrast, GG increased them. The data from dough assessment showed that none of the additives changed the quality and processability. Furthermore, the outcomes from the physical and instrumental assessments of the breads indicated that although there were some modifications in the bread quality, the FI did not change the quality of the breads drastically. The sensory evaluation results showed that the FI addition resulted in acceptable sensory attributes and palatability. The results also showed that some of the sensory attributes were significantly improved through adding the FI. The scanning electron microscopy (SEM) images clearly demonstrated the influence of the FI on the starch granules gelatinisation. It is very evident that the granules are less swollen when DFs are added. The in vivo trial results indicate that DFs incorporated into bread could change the digestibility of starch and lowered the GR in comparison to the controls. This could be attributed to a number of factors. Gelatinisation may influence the granule structure and degree of amylase and amylopectin readily solubilised. The gels formed by DFs could restrict the accessibility of α-amylase to the starch granules. A mechanism would be linked to viscous layers of soluble DFs becoming physical barriers which could limit the uptake of digested carbohydrate in the small intestine.

Document Type

Thesis

Publication Date

2014-01-01

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