# Volatile Organic Compounds in Breads Prepared with Different Sourdoughs
###### Abstract  
Sourdough is an old example of a natural starter composed of a mixture of flour, water, and metabolites and is produced by naturally occurring lactic acid bacteria and yeasts that influence bread aroma. In this work, four types of sourdough were used to prepare bread: one sourdough with yeast beer and three with bacteria and yeasts. The physicochemical parameters (pH, moisture, water activity, and organic acids) of the bread and sourdoughs were assessed. Lactic, acetic, and succinic acids were found in considerable amounts in sourdoughs and the corresponding breads. The fermentation quotient (molar ratio between lactic and acetic acid) ranged from 0.39 to 3.4 in sourdoughs. Lactic acid was prevalent in all types of bread and showed the highest value in bread made from sourdough with a 1.5 bacteria/yeast ratio (8722.24 mg/kg). Moreover, volatile organic compounds were identified in bread samples. Alcohols, aldehydes, and acetic acid were mainly found. The alcohol concentration ranged from 140.88 to 401.20 mg/g. Aldehydes ranged from 185.01 to 454.95 ng/g, and acetic acid ranged from 91.40 to 173.81 ng/g. bread prepared from sourdough with a 1.5 bacteria/yeast ratio showed a considerable amount of alcohols and acetic acid.  
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Footnote †: journal: Medical  
sourdough can be dried. This type of sourdough is convenient for preserving authentic bread taste as a product of the bakery industry [2]. In addition, variations in the types of starter cultures can be used in the fermentation process. Additionally, the fermentation conditions (temperature, time, pH) may differ significantly with the process applied [8].  
The generation of volatiles in sourdoughs is clearly influenced by the activity of the LAB and yeasts, and factors influencing their activity determine the amounts of metabolites formed. Generally, LAB are mostly responsible for acidification, while both types of microbes are able to liberate aroma precursors, such as free amino acids, and their concentrations increase significantly during sourdough fermentation [6,8,9]. Sourdough is mainly used to improve the aroma of wheat bread.  
During baking, the raw dough is converted into a brown-colored product. The ingredients used for the preparation of bread are important to develop the bread's aromatic profile. Different steps can influence the aromatic profile of bread, such as dough fermentation by yeasts and/or LAB, enzymatic activity, and thermal reaction developed during bread baking [10]. The flavor of bread crumb is influenced mainly by enzymatic reactions during dough fermentation, whereas the flavor of bread crust is more influenced by thermal reactions during the baking process, such as the nonenzymatic Maillard reactions and caramelization of sugars [11].  
More than 300 identified volatile organic compounds belonging to different chemical classes, such as acids, aldehydes, ketones, alcohols, esters, and sulfide compounds, are produced during fermentation and cooking.  
The use of sourdough LAB and yeasts increases the aromatic quality of bread; in fact, the use of LAB (homo- and heterofermentative) and yeasts influences the profile of volatile organic compounds [12]. Soundoughs are characterized by high alcohol concentrations, aldehydes, ketones, esters, acids, and terpen [13].  
Furthermore, sourdough fermentation influences the rheological, sensory, and shelf-life attributes of bakery products. Recently, the effects of sourdough fermentation on several functional/nutritional aspects of baked products were shown. Some aspects, such as the potential of a lower glycemic index to increase mineral bioavailability as well as decrease the gluten content, have been almost completely elucidated [14].  
Therefore, the present work aimed to evaluate the influence of four different sourdoughs with different ratios of bacteria/yeasts prepared with different types of wheat flour on both volatile organic compounds and organic acid concentrations of bread.