Production of flavour-active methionol from methionine metabolism by yeasts in coconut cream

Yeasts Candida kefyr NCYC143, Candida utilis CUM, Kluyveromyces lactis KL71, Saccharomyces bayanus SB1, Saccharomyces cerevisiae EC1118, Saccharomyces chevalieri CCICC1028, Candida famata (previously Torulopsis candida) CCICC1041 and Williopsis saturnus var. saturnus CBS254 were screened for their ability to produce flavour-active methionol (3-methylthio-1-propanol) in coconut cream supplemented with l-methionine. The yeasts varied with their ability to produce methionol from methionine with Saccharomyces cerevisiae EC1118 producing the most, followed by Kluyveromyces lactis KL71. Little methionol was produced by the other yeasts. Methionol production by Kluyveromyces lactis KL71 was subjected to further studies under different conditions of initial pH (4.0–6.3), temperature (20–33 °C), l-methionine concentration (0.05–0.25%) and yeast extract concentration (0-0.50%); optimal conditions were established at pH 5.0, 33.0 °C, 0.15% l-methionine and 0.05% yeast extract. CharmAnalysis™ using SPME-GC-MS was conducted on the coconut cream ferment; methional (3-methylthio-1-propanal), methionol and 2-phenylethyl acetate were found to be the most potent aroma-active compounds. The product of coconut cream fermentation by Kluyveromyces lactis KL71 may be considered as a novel, plant-based, natural and complex flavoring bioingredient in food applications.