Reference Number: 131
Background: Sourdough has been used in bread production for decades to improve its preservation, texture and flavor. Today it is mostly used as a bread flavor improver. For many years, bread volatile compounds have been referenced and more than 540 have now been reported. In contrast, sourdough volatile compounds have been less studied. No listing of these compounds has been previously carried out and their origins have not been reported in a review.
Scope and Approach: The scope of this review is to detail the volatile compounds previously reported in sourdough and sourdough bread in order to highlight the most common ones. Methods for studying volatiles in sourdough and sourdough bread are first listed. Then the volatile compounds identified from previous papers about sourdough aroma are characterized to understand their origins and their contribution to bread aroma.
Key Findings and Conclusions: To date, 196 volatile compounds have been reported in sourdough and sourdough bread including 43 aldehydes, 35 alcohols, 33 esters, 19 ketones, 14 acids, 13 furans, 11 pyrazines, 2 lactones, 2 sulfurs, 21 others and alkanes. The most recent characteristics of most of these volatile compounds (origins, odors and odor thresholds) are reported as well as their presence in sourdough, sourdough bread or bread. This report underlines the production levers that could modify sourdough and bread aroma.
SIGNIFICANCE OF THIS STUDY
The review provides an overview of the main volatile compounds in sourdough starters and bread with the major origins of these volatile compounds and their influential factors.
The main precursors of volatile compounds in sourdough and sourdough bread are carbohydrates, aldehydes, amino acids, lipids and fatty acids which undergo processes such as fermentation (driven my sourdough microflora), lipid oxidation (driven by mixing, storage) and Maillard reaction (driven by the baking process). Each process creates a range of volatile compounds. For example, the process of fermentation results in the formation of acids, alcohols, esters and ketones and the process of mallard reaction results in the formation of parazines, pyridines, pyroles, sulfurs, ketones and aldehydes. It is often difficult to establish a link between a given compound and a single-generation pathway, as the same compound can originate from several pathways. However, a combination of these processes or pathways is what contributes the unique flavours and aromas that are associated with sourdough and sourdough breads. The paper also highlights the importance of the sourdough process on the concentration and variety of volatile flavour molecules. It states that the impact of sourdough on bread aroma depends on the proportion of sourdough in bread dough. Previous researchers have shown that some volatile compound contents in SD- bread are related to their concentrations in the corresponding sourdough but are usually lower. This can be explained by the proportion of sourdough in bread dough and by the impact of bread processes. Also when comparing the flavour profile between sourdough and yeast fermented breads, sourdough breads volatile profiles were more complex with LAB fermentation than with yeast fermentation, mainly for the ester content. The major characteristic of yeast fermented breads was the high acid content. Furthermore, when the authors compared wheat sourdough with wheat sourdough bread and rye sourdough with rye sourdough bread, they found that the volatiles from fermentation were the main variation factors between these products. However, there were some differences between wheat and rye products: alcohols and esters were more described in wheat products whereas aldehydes, furans and sulfurs are more cited in rye products.