INFLUENCE OF SOURDOUGH STARTER CULTURE ON BREAD TEXTURE AND STALING

Abstract

INFLUENCE OF SOURDOUGH STARTER CULTURE ON BREAD TEXTURE ANDSTALING The world is experiencing a global food waste crisis, and one of the top contributors to this is from bread waste. A main reason that bread is wasted is due to staling, a chemical process that occurs via starch retrogradation. This is a process driven by the primary carbohydrates in starch, amylose and amylopectin, and results in flavor and moisture loss, as well as crumb firmness. As consumers push for more clean-label products, an approach that can increase staling without the use of preservatives is through sourdough fermentation. Sourdough fermentation is done by a unique “starter” culture, which consists of wild bacteria, yeasts, and fungi, spawning as a product of the surrounding environment. These unique microbial systems ferment the starch in sourdough to produce organic acids and bioactive molecules. A unique byproduct produced by some sourdough bacterial fermentations are exopolysaccharides (EPS). EPS are known to exhibit a positive influence on bread flavor, texture, and shelf-life when added to wheat breads. They are also an FDA generally certified as safe (GRAS) ingredient and clean label. The aim of this research is to identify how unique microbial communities in sourdough starters produce EPS through natural fermentation, and how the characteristics of produced EPS influence shelf-life. Bread staling was measured through a crumb firmness test (AACC 74-09) over a two-week period. EPS were extracted by an ethanol extraction and quantified via a phenol-sulfuric acid assay. The size of extracted EPS was measured by DLS. The sourdough samples were characterized into taxa by metabolomic sequencing. The relationship between bacterial species and genes were examined through a spearman correlation, revealing that EPS size and quantity may be inversely related. There also may be a competitive pathway between EPS production and iii glucose-1-phosphate, regardless of bacterial species. More research is needed examining the genetic pathways between EPS production and bacterial species, as well as their interaction with the environment. This study reveals the importance of understanding EPS production within a food matrix, not just as an external addition. It also reveals that EPS production could be influenced more by genetic pathways and gene activation than by specific species.