The modulatory effect of guar gum on freeze-thaw stability of cooked oat roll

Oat roll is a traditional Chinese food made of whole oat flour. The purpose of this work was to investigate the role of guar gum on starch retrogradation and water migration of cooked oat roll during freeze-thaw cycles by low-field nuclear magnetic resonance (LF-NMR) measurement, differential scanning calorimetry (DSC) and so on. The results showed that freeze-thaw cycles affected the migration of strong bound water to weak bound water and free water, and thus deteriorated the quality of products. As the addition of guar gum increased, the water mobility and the consequent water loss caused by the freeze-thaw cycles were significantly reduced. The addition of 0.3 % and 0.5 % guar gum could decrease the number and size of pores in cooked oat roll, enhanced the water absorption and gelatinization capacity. Moreover, hindered rearrangement of starch molecular chains to delay retrogradation by restricting the water mobility. Finally the increase of hardness caused by freeze-thaw cycles was decelerated. However, 1 % added amount of guar gum due to its excessive viscosity, caused hindrance to the water absorption and gelatinization of starch granules. Resulted in a greater increase in hardness and adhesiveness, which reduced the edible quality.