Real-Time Monitoring of Volatile Compounds Losses in the Oven during Baking and Toasting of Gluten-Free Bread Doughs: A PTR-MS Evidence

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.

Sourdough Microbiome Comparison and Benefits

“…In addition, the fermentation process of sourdough is highlighted to bring more flavour, complexity, aroma and better texture of bread due to LAB enzymatic hydrolysis processes and the generation of compounds in the Maillard reaction during the baking process [ 23 , 24 ]. The formation of flavour volatiles in sourdough is contributed by proteolytic processes of amino acids, conversion of glutamine released from cereal proteins to glutamate, and conversion of arginine to ornithine by LAB during baking which have a profound influence in a more tangy and roasty sourdough taste.…”

Elucidation of the non-volatile fingerprint in oven headspace vapor from bread roll baking by ultra-high resolution mass spectrometry

“…We were able to calculate models for 991 features with an adjusted R 2 value > 0.6. Reflections upon response surface models of selected features in oven vapor permit us to follow the release of molecules during the cooking of foodstuff similar to Pico et al who classified VOC based on the shape of their liberation curves during baking and toasting (Pico et al, 2020). Two easily interpretable examples are shown in Fig.…”

“…Oven vapor is drawn by a negative pressure system out of a baking chamber and condensed in a round bottom flask for later analysis. related analytical work on oven vapor was executed by proton transfer reaction PTR-MS (Pico et al, 2020;Wieland et al, 2012). In PTR-MS volatile organic compounds (VOC) are ionized by transferring a proton from H 3 O + ions to analytes having a greater proton affinity than water.…”

“…In the few cases when its headspace was studied during processing, most protocols focused on the analysis of volatile molecules contained in the vapor. In particular, solid-phase microextraction (SPME) coupled to gas chromatography with mass spectrometric detection (GC-MS) (Rega, Guerard, Delarue, Maire, & Giampaoli, 2009;Rochat & Chaintreau, 2005) and proton transfer reaction (PTR) MS (Pico, Khomenko, Capozzi, Navarini, & Biasioli, 2020;Wieland et al, 2012) were used to study aroma active compounds evolving during thermal processing. Both approaches focus on the analysis of volatile compounds.…”

Real-Time Monitoring of Miniaturized Thermal Food Processing by Advanced Mass Spectrometric Techniques

“…3,4 Likewise, baking often is the final stage during preparation of cereal products. 5,6 Hence, the understanding of baking processes at a molecular level is of immediate interest to several alimental industries with regard to flavor generation and product quality.…”