|Yokoyama, Wallace - Wally|
Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2010
Publication Date: 2/11/2011
Publication URL: http://sciencedirect.com/science/article/pii/S0144861710009458
Citation: Rosell, C., Shoemaker, C.F., Yokoyama, W.H. 2011. Rheology of different hydrocolloids–rice starch blends. Effect of successive heating–cooling cycles. Carbohydrate Polymers. 84(1): 373-382. Interpretive Summary: Cereal starches are the main source of metabolizable energy and combined with other ingredients to form breads, pastas, sauces, and other foods. Modern food processes incorporate many food modifiers including polysaccharide based gums. These gums interact with starch to modify their textural properties. We studied three different types of commonly used food gums: guar, xanthan and hydroxypropylmethylcellulose. A very sensitive, structure preserving instrument was used to measure viscosity and elasticity as a function of gum concentration, cooking and time. The three different gums interacted with starch to produce different levels of thickness during cooking and after cooling.
Technical Abstract: Hydrocolloids are frequently used for modifying starch functionality. In the present study the possible interaction of three different hydrocolloids - guar gum, hydroxypropylmethylcellulose (HPMC) and xanthan gum - with rice starch was explored by determining the pasting, viscoelastic and swelling properties of the rice starch-hydrocolloids mixtures. The impact of succesive heating-cooling cycles on the pasting, viscoelasticity and swelling was also determined. Hydrocolloids tested in the range 0.2-0.8% (w/w) significantly modified the pasting, viscoelastic and swelling properties of rice starch-hydrocolloid pastes (8%, w/w) and the extent of the effect was dependent on hydrocolloid concentration. Guar and xanthan gum mixtures with rice starch had the greatest effect on the pasting properties, whereas HPMC mixtures only changed the viscosity during cooling. The starch-hydrocolloids pastes formed weaker gels compared to those of the starch alone. Rheological results suggested the formation of composite network structures with high frequency dependence. Succesive multiple-heating cycles allowed the gel to rearrange resulting in altered gel viscoelasticity and release of water soluble compounds that favor phase separation at the highest hydrocolloid level tested.