title: Harvesting yeast (Saccharomyces cerevisiae) at different physiological phases significantly affects its functionality in bread dough fermentation.
abstract: Fermentation of sugars into CO2, ethanol and secondary metabolites by baker's yeast (Saccharomyces cerevisiae) during bread making leads to leavening of dough and changes in dough rheology. The aim of this study was to increase our understanding of the impact of yeast on dough related aspects by investigating the effect of harvesting yeast at seven different points of the growth profile on its fermentation performance, metabolite production, and the effect on critical dough fermentation parameters, such as gas retention potential. The yeast cells harvested during the diauxic shift and post-diauxic growth phase showed a higher fermentation rate and, consequently, higher maximum dough height than yeast cells harvested in the exponential or stationary growth phase. The results further demonstrate that the onset of CO2 loss from fermenting dough is correlated with the fermentation rate of yeast, but not with the amount of CO2 that accumulated up to the onset point. Analysis of the yeast metabolites produced in dough yielded a possible explanation for this observation, as they are produced in different levels depending on physiological phase and in concentrations that can influence dough matrix properties. Together, our results demonstrate a strong effect of yeast physiology at the time of harvest on subsequent dough fermentation performance, and hint at an important role of yeast metabolites on the subsequent gas holding capacity.
authors.affiliation: Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Molecular and Microbial Systems, KU Leuven, Kasteelpark Arenberg 20, Box 2463, B-3001 Leuven, Belgium.
authors.forename: Mohammad N
authors.initials: MN
authors.lastname: Rezaei
authors.affiliation: Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Molecular and Microbial Systems, KU Leuven, Kasteelpark Arenberg 20, Box 2463, B-3001 Leuven, Belgium.
authors.forename: Emmie
authors.initials: E
authors.lastname: Dornez
authors.affiliation: Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Molecular and Microbial Systems, KU Leuven, Kasteelpark Arenberg 20, Box 2463, B-3001 Leuven, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Jacobs
authors.affiliation: Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Molecular and Microbial Systems, KU Leuven, Kasteelpark Arenberg 20, Box 2463, B-3001 Leuven, Belgium.
authors.forename: Anali
authors.initials: A
authors.lastname: Parsi
authors.affiliation: VIB Laboratory for Systems Biology & CMPG Laboratory for Genetics and Genomics, KU Leuven, Bio-Incubator, Gaston Geenslaan 1, B-3001 Leuven, Belgium.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Verstrepen
authors.affiliation: Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Molecular and Microbial Systems, KU Leuven, Kasteelpark Arenberg 20, Box 2463, B-3001 Leuven, Belgium. Electronic address: christophe.courtin@biw.kuleuven.be.
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Courtin
mesh_terms: D001939:Bread / Q000032:analysis / Q000382:microbiology*; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D000431:Ethanol
keywords: Diauxic shift; Dough; Fermentation rate; HPLC; High performance liquid chromatography; OD(600); Optical density at 600 nm; Organic acids; Physiological phase; Rheofermentometer; Saccharomyces cerevisiae; TCA cycle; Tricarboxylic acid cycle; YPD; YPS; Yeast; Yeast peptone dextrose; Yeast peptone sucrose; Yx; pH; yeast cells harvested at harvest point x