| The overall objective of this research was to develop and improve quality of gluten free (GF) oat flour breads using sourdough technology using two different types of lactic acid bacteria (LAB) , L. Plantarum (LP) and L. Sanfranscensis (LS).Thermo-mechanical rheofermented properties of oat flour dough with LAB sourdough starters and chemically acidified starters were determined with Mixolab and Rheofermentometer. Quality of GF oat sourdough breads produced with different sourdough starters were studied with specific volume, height, baking loss, texture, and sensory analysis. The staling and staling rate of GF oat sourdough breads was analyzed through the determination of moisture content, moisture migration, water activity, amylopectin retrogradation enthalpy change during the 5-days storage period. The changes of oat starch properties during lactic acid bacteria fermentation was also studied by extracting starch after LAB fermentation.At the beginning of the fermentation, the pH of oat dough fermented with LP decreased faster than the oat dough fermented with LS, however, at the end of fermentation, their pH are almost the same. The TTA values of oat dough fermented with LP is also higher than LS. The cell number of lactic acid bacteria increased sharply at first then reached to maximum , the cell number of LP is higher than LS, which indicated the oat flour was better for LP than LS.The addition of sourdough starters at what level (10% or 20%) decreased the dough development time (from 18.4 to 15. 3 min for LP and to 15.6 min for LS), water absorption (from 89 to 81.5% for LP and 82.5% for LS) and stability (from 12.3 to 9.6 min for LP and to 9.0 min for LS), aggravated dough weakening but maintained viscoelasticity. The addition of 10% sourdough starter with LP promoted (increased) dough expansion height (Hm) and gas holding capacity, accelerated starch gelatinization rate, inhibited staling, and improved cooking stability. Chemical acidification destroyed dough stability and viscoelasticity, and decreased dough expansion height, fermentation tolerance and gas holding capacity.The specific volume of oat bread increased significantly(P>0.05) with 10% LP sourdough, however, when the addition increased to 20%, the specific volume did not increased and as same as control bread (Non-sourdough). The baking loss of bread depends on the addition of water in the formula, the baking loss of bread with HPMC is higher than the bread without HPMC, the addition of sourdough have no significant effect on the baking loss of bread. The hardness of oat bread reduced significantly with the addition of the HPMC, especially, the bread with 10% LP and 20% LS have lowest hardness. The sensory sore of bread with 10% LP was highest, however, when the addition of sourdough increased to 20%, the sensory score decreased due to the lower specific volume, harder texture and too much acid. It showed that the moisture migration rate of sourdough bread is lower than the non-sourdough bread and chemical acid bread; during the storage, the water activity of all the sample did not change significantly. The hardness of bread increased during the storage. The amylopectin retrogradation enthalpy was increased during the storage. The addition of the sourdough reduced the retrogradation enthalpy significantly.Extract starch from fermented oat dough showed the amylose content increased during the fermentation which induced the swelling power of the starch decreased, this is can explain the reason that dough stabilization decreased after adding the sourdough. The results of RVA and DSC indicated that the peak viscosity decreased with the fermentation time increased. The onset gelatinization temperatures were lower. The time of gelatinization was longer than control sample, the gelatinization enthalpy was increased and the percentage of retrogradation was decreased. The gel strength of fermented sample was lower than the control and the amylase content was increased during the fermentation.
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