Table 1.
Yeast species tested for their potential in bread making.
Table 2.
Volatile compounds identified and quantified in bread crumb of breads made with two non-conventional strains (Torulaspora delbrueckii Y273 and S. bayanus Y156) or commercial baker’s yeast (control Y243) using HS-SPME-GC-MS.
Fig 1.
Small-scale fermentation tests for ten selected nonconventional yeasts.
(A) Four strains (shown in gray font) were found to produce biogenic amines. (B) Small-scale growth assays using a Bioscreen C apparatus shows the growth curves of the different strains, the arrows show the harvest point (late diauxic shift/ early stationary phase). (C) CO2 production of the six strains that did not show biogenic amine production during dough fermentation as measured in the Risograph.
Fig 2.
Sensory analysis and leavening ability of non-conventional yeasts compared to commercial bakery control yeast.
(A) Triangle tests with a 20-person consumer panel show that out of six bread samples produced with different yeasts, two samples (fermented with Torulaspora delbrueckii Y273 and S. bayanus Y156) yielded bread that was recognized as being significantly (** = p < 0.01) different by the sensory panel members when compared to bread produced with the control commercial bakery strain. The difference in smell was more pronounced than the difference in taste. Bar graphs represent the percentage (± 95% confidence limits) of participants that correctly identified the odd sample in a triangle test and noticed the difference between the sample and the control. Significance levels were calculated using binomial tests based on the deviation from the 33% of correct identifications as expected by chance. (B) Fermentation with Y156 results in a slightly smaller loaf of bread compared to the control while the volume of the bread fermented by Y273 is comparable to that of the control.
Fig 3.
Heatmaps illustrating the differences in relative concentrations of volatile compounds in bread crumb prepared with nonconventional yeasts (A) Torulaspora delbrueckii (Y273) and (B) S. bayanus (Y156) compared to bread produced with a commercial baker strain (control). Data are based on HS-SPME-CG-MS analysis of two biological replicates with four technical replicates each. Color codes indicate the fold difference in log2-transformed relative peak areas of each compound, between samples and their controls. P-values were obtained using a linear mixed models and Tukey posthoc analysis, in which biological replicate and treatment were coded as random and fixed factors.
Table 3.
Overview of compounds that showed differences between breads produced with two nonconventional strains (Torulaspora delbrueckii Y273 and S. bayanus Y156) and commercial baker’s yeast (control Y243).
All of these compounds have Odor Activity Values** (OAV) > 0.1 and Flavor Dilution*** (FD) factors > 8 [45].