Production of Type III Sourdough by Spray- and Freeze-Drying Focusing on Organic Acids, Volatile Organic Compounds, and Cell Viability During Storage

Abstract

Sourdough fermentation using indigenous lactic acid bacteria (LAB) is one of the oldest techniques used by humanity. The selection of strains for fermentation makes this process suitable for industrial applications. Type III sourdough is obtained by dehydrating liquid sourdough, facilitating its application, storage, and transportation. This study aimed to produce type III sourdough using freeze- and spray-drying, using three selected LAB combinations. Total titratable acidity and pH were not affected by drying methods. There were significant reductions in the content of organic acids after atomization. In contrast, lyophilization preserved lactic, acetic, and propionic acids, with the first being the most abundant. The viability of LAB after the spray-drying process showed an average reduction of 2.0 log CFU g^–1, reaching less than <1.0 log CFU g^–1 after 120 days of storage. Freeze-drying was more effective, with counts of 9.0 log CFU g^–1 at the beginning and an average of 7.0 log CFU g^–1 in 120 days of storage. This study also evaluated the volatile organic compounds (VOCs) of sourdough after drying, revealing the presence of compounds such as 1-pentanol, benzaldehyde, ethyl hexanoate, and 2-pentylfuran, originating from matrix fermentation and oxidation processes. Freeze-drying better preserved organic acids and the viability of LAB, despite high production costs. Spray-drying showed promise for maintaining LAB viability. Although new VOCs are generated during dough fermentation and baking, this study shows that the sourdough VOCs composition varied little between the drying methods, indicating potential applications in baking.