Abstract
Losses of volatile compounds during baking are expected due to their evaporation at the high temperatures of the oven, which can lead to a decrease in the aroma intensity of the final product, which is crucial for gluten-free breads that are known for their weak aroma. Volatiles from fermentation and lipids oxidation are transferred from crumb to crust, and they flow out to the air together with Maillard and caramelisation compounds from the crust. In this study, the release to the oven of volatile compounds from five gluten-free breads (quinoa, teff and rice flours, and corn and wheat starches) and wheat bread during baking and toasting was measured in real-time using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS). Baking showed different volatile release patterns that are described by bell-shaped curves, plateaus and exponential growths. Flour-based breads had the higher overall volatile release during baking, but also high ratios in the final bread, while starch-based breads showed high pyrazine releases due to moisture losses. Meanwhile, toasting promoted the release of volatile compounds from the bread matrix, but also the additional generation of volatiles from Maillard reaction and caramelisation. Interestingly, gluten-free breads presented higher losses of volatiles during baking than wheat bread, which could partially explain their weaker aroma.
Highlights
Bread is one of the most consumed staple foods all over the world, since it is eaten daily, which makes it an important socio-economic product in human nutrition [1]
Thirty-nine volatile compounds were confirmed by means of fast GC-proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) using pure standards, while the other 15 were tentatively identified based on their m/z, possible formula, and literature about bread aroma
54 volatile compounds were selected as important contributors of bread aroma [17], including alcohols, aldehydes, ketones, acids, esters, terpenes, furans, pyrroles, pyrazines, and the presence of 39 of them was verified examining the presence of the m/z found with standards that were injected by fast-GC-PTR-ToF-MS (Supplementary Table S1)
Summary
Bread is one of the most consumed staple foods all over the world, since it is eaten daily, which makes it an important socio-economic product in human nutrition [1]. The sensorial quality of bread undoubtedly determines its consumption, including characteristics, such as volume, texture, colour, and flavour, with the latter understood as the sum of the gustative and olfactory impressions experienced during eating [2]. All of this explains the continuous research activities on how to improve its sensory, chemical, and industrial characteristics [1]. Among these fundamental properties, the aroma of bread plays a key role in its acceptance by consumers [3]. The aroma of bread crust has been characterised by volatile compounds
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