title: Influence of different proteolytic strains of Streptococcus thermophilus in co-culture with Lactobacillus delbrueckii subsp. bulgaricus on the metabolite profile of set-yoghurt.
abstract: Proto-cooperation between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus is one of the key factors that determine the fermentation process and final quality of yoghurt. In this study, the interaction between different proteolytic strains of S. thermophilus and L. delbrueckii subsp. bulgaricus was investigated in terms of microbial growth, acidification and changes in the biochemical composition of milk during set-yoghurt fermentation. A complementary metabolomics approach was applied for global characterization of volatile and non-volatile polar metabolite profiles of yoghurt associated with proteolytic activity of the individual strains in the starter cultures. The results demonstrated that only non-proteolytic S. thermophilus (Prt-) strain performed proto-cooperation with L. delbrueckii subsp. bulgaricus. The proto-cooperation resulted in significant higher populations of the two species, faster milk acidification, significant abundance of aroma volatiles and non-volatile metabolites desirable for a good organoleptic quality of yoghurt. Headspace SPME-GC/MS and (1)H NMR resulted in the identification of 35 volatiles and 43 non-volatile polar metabolites, respectively. Furthermore, multivariate statistical analysis allows discriminating set-yoghurts fermented by different types of starter cultures according to their metabolite profiles. Our finding underlines that selection of suitable strain combinations in yoghurt starters is important for achieving the best technological performance regarding the quality of product.
authors.affiliation: Dairy Science and Technology Group, Chair of Food Quality and Design, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Sarn
authors.initials: S
authors.lastname: Settachaimongkon
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: M J Robert
authors.initials: MJ
authors.lastname: Nout
authors.affiliation: Dairy Science and Technology Group, Chair of Food Quality and Design, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Elsa C
authors.initials: EC
authors.lastname: Antunes Fernandes
authors.affiliation: Dairy Science and Technology Group, Chair of Food Quality and Design, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Kasper A
authors.initials: KA
authors.lastname: Hettinga
authors.affiliation: Laboratory of Biochemistry, Wageningen University, P.O. Box 8128, 6700 ET Wageningen, The Netherlands.
authors.forename: Jacques M
authors.initials: JM
authors.lastname: Vervoort
authors.affiliation: Dairy Science and Technology Group, Chair of Food Quality and Design, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Toon C M
authors.initials: TC
authors.lastname: van Hooijdonk
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Marcel H
authors.initials: MH
authors.lastname: Zwietering
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Eddy J
authors.initials: EJ
authors.lastname: Smid
authors.affiliation: Dairy Science and Technology Group, Chair of Food Quality and Design, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: hein.vanvalenberg@wur.nl.
authors.forename: Hein J F
authors.initials: HJ
authors.lastname: van Valenberg
mesh_terms: D000818:Animals; D005285:Fermentation; D005516:Food Microbiology; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D048668:Lactobacillus delbrueckii / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D055432:Metabolomics; D008892:Milk / Q000737:chemistry*; D015999:Multivariate Analysis; D048249:Streptococcus thermophilus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D055549:Volatile Organic Compounds / Q000032:analysis; D015014:Yogurt / Q000032:analysis* / Q000382:microbiology* / Q000592:standards
chemical_list: D055549:Volatile Organic Compounds
keywords: Dairy; Fermented milk; Flavor; Metabolomics; Protease; Starter culture