Effect of Wheat Flour Extraction Rates on Physico-Chemical Characteristics of Sourdough Flat Bread

Abstract

The project was designed to determine the suitability of different wheat varieties for the production of naan and to evaluate the performance of mixed starter cultures of yeast and LAB and wheat flour extraction rates on the quality of sourdough naan. On the basis of physico-chemical, rheological characteristics of wheat flour and sensory characteristics of the naan, wheat variety AS-2002 were found the most suitable for the production of naan. Consequently, this variety was milled to get 64, 76, 88 and 100% extraction rates flour for subsequent studies. The extraction rates significantly influenced the proximate composition and rheological characteristics of the flour. The sourdoughs were prepared from different extraction rates flour using freeze dried mixed cultures namely; LA-1 containing homo-fermentative strain Pediococcus acidilacti and yeast Saccharomyces cerevisiae and LA-5, containing hetero-fermentative strain L. brevis and homo-fermentative strain L. casei and yeast Saccharomyces cerevisiae. The pH of the sourdoughs decreased and acidity increased significantly with an increase in extraction rate of flour. The sourdoughs were analyzed for volatiles; the compounds extracted were alcohols, esters, acids, carbonyls and aromatic compounds. The sourdough naans were prepared by using different extraction rates flour. The production of organic acids increased with an increase in extraction rate and freeze dried cultures containing heterofermentative strains of LAB showed better performance than homo-fermentative in the production of organic acids. The sourdough naans prepared with different extraction rates flour showed highly significant effect on minerals contents. The volatile compounds extracted from the sourdough naans using SPME and Dynamic Headspace techniques were mainly identified as alcohols, esters, carbonyls. It was found that heterofermentative strains of LAB produced more volatile compounds than homo-fermentive and SPME technique extracted volatile compounds with higher relative peak areas than Dynamic Headspace. The sensory evaluation of naans revealed that the sourdough naans were preferred over yeast leavened due to their better taste; flavor and chewability. The sourdough naans prepared from 76% extraction rate flour were awarded the highest scores for most of the sensory attribute.