Proton‐transfer‐reaction mass spectrometry for the study of the production of volatile compounds by bakery yeast starters

Abstract

The aromatic impact of bakery yeast starters is currently receiving considerable attention. The flavor characteristics of the dough and the finished products are usually evaluated by gas chromatography and sensory analysis. The limit of both techniques resides in their low-throughput character. In the present work, proton-transfer-reaction mass spectrometry (PTR-MS), coupled to a time-of-flight mass analyzer, was employed, for the first time, to measure the volatile fractions of dough and bread, and to monitor Saccharomyces cerevisiae volatile production in a fermented food matrix. Leavening was performed on small-scale (1 g) dough samples inoculated with different commercial yeast strains. The leavened doughs were then baked, and volatile profiles were determined during leavening and after baking. The experimental setup included a multifunctional autosampler, which permitted the follow-up of the leavening process on a small scale with a typical throughput of 500 distinct data points in 16 h. The system allowed to pinpoint differences between starter yeast strains in terms of volatile emission kinetics, with repercussions on the final product (i.e. the corresponding micro-loaves). This work demonstrates the applicability of PTR-MS for the study of volatile organic compound production during bread-making, for the automated and online real-time monitoring of the leavening process, and for the characterization and selection of bakery yeast starters in view of their production of volatile compounds.

Mead fermentation monitoring by proton transfer reaction mass spectrometry and medium infrared probe

“…This was measured at m/z 21, which arises from the 18 The mean values of the signal intensities from the 6th to 10th scan cycle were calculated for each mass in the range from m/z 20 to m/z 200. Only signals showing a minimum intensity of 500 normalized counts per second (ncps) in at least one of the samples analysed were used for data analysis.…”

“…Through the evolution of some volatile organic compounds, it was possible to correlate classic microbiological parameters like cell density, pH or O 2 and CO 2 concentrations within the off-gas. PTR-MS was also employed in the study of lactic acid fermentation of milk [14,15] or dough leavening [18]. PTR-MS was used to monitor fermentation progress and to determine the kinetics of production or consumption of different volatile organic compounds.…”

Monitoring of lactic fermentation driven by different starter cultures via direct injection mass spectrometric analysis of flavour-related volatile compounds

“…In previous works, PTRToF-MS has been employed to monitor VOC kinetics during LAF in milk , or in correlation with textural properties, transglutaminase and heat treatments of yogurt Tsevdou et al, 2013). Moreover, PTR-ToF-MS has been recently used to monitor and differentiate starter cultures employed in the bakery sector (Makhoul et al, 2014).…”

Sensory, spectrometric (PTR–ToF–MS) and chemometric analyses to distinguish extra virgin from virgin olive oils

“…This technique was reported to have several applications in the field of food aroma analysis of ham (Sánchez del Pulgar et al 2011), saffron (Masi et al 2015a, b), bakery yeast starters (Makhoul et al 2014), and dried porcini mushrooms aroma (Aprea et al 2015).…”

“…The utilized gas-chromatographic analytical methods, although valuable and, in many cases, essential, have some disadvantages such as the low time resolution, the laborious sample preparation and the long operation time; different alternative analytical methods have been proposed , and as faster alternative technique it can be considered the direct headspace proton transfer reaction, time of flight, mass spectrometry (PTR-ToF-MS) Makhoul et al 2014).…”