Biogeneration of 2-(1-hydroxyethyl)-4,5-dihydrothiazole as precursor of roasted and popcorn-like aroma for bakery products

Bread aroma is one of the most important criteria of the quality of bakery product. Molecules exhibiting roasted notes largely contribute to this flavour and 2-acetyl-2-thiazoline (2-AT) was identified as one of the strongest. We report here the formation of its precursor 2-(1-hydroxyethyl)-4,5-dihydrothiazole via the bioconversion of cysteamine, ethyl-l-lactate and d-glucose with baker’s yeast as biocatalyst. The microbial reduction of the carbonyl group of 2-acetyl-2-thiazoline using the same microorganism is an alternative to produce the target precursor in good yield (up to 60%). Heat treatment of 2-(1-hydroxyethyl)-4,5-dihydrothiazole generated attractive and intensely roasted, popcorn-like and bread crust-like notes. High amounts of 2-acetyl-2-thiazoline were detected in the heated samples. Finally, the addition of the precursor significantly enhanced the aroma of pizza bread when mixed into the dough.