Formation of Volatile Sulfur-Containing Compounds by Saccharomyces cerevisiae in Soymilk Supplemented with L-methionine

• Published in: Food biotechnology 2011-10, Vol.25 (4), p.292-304
• Main Authors: Quek, Jasmine Mei Bei, Seow, Yi-Xin, Ong, Peter K.C, Liu, Shao-Quan
• Format: Article
• Language: English
• Subjects: Amino acids; Aroma compounds; cheeses; Fermentation; Fermented food; fermented foods; flavor; Flavor compounds; Flavors; Food; Gas chromatography; mass spectrometry; Mass spectroscopy; Metabolism; methional; methionol; Milk; Odor; odor compounds; odors; Perception; pH effects; Saccharomyces cerevisiae; solid phase extraction; Solid phase methods; Soybeans; soymilk; Sulfur; temperature; Temperature effects; Volatiles; Yeast; yeast extract; yeasts
• ISSN: 0890-5436; 1532-4249; 1532-4249
• DOI: 10.1080/08905436.2011.617254

The formation of volatile sulfur-containing flavor compounds from L-methionine catabolism by Saccharomyces cerevisiae EC-1118 was investigated in soymilk supplemented with this sulfur-containing amino acid with a focus on methionol (3-methylthio-1-propanol). Methionol produced from L-methionine metabolism of yeast in soymilk was extracted by solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). The effects of time (0 - 72 h), L-methionine concentration (0.05-0.20%), yeast extract concentration (0.00-0.30%), initial medium pH (4.5-6.9), and temperature (25-34°C) on the production of methionol were investigated. One-liter scale-up fermentation of soymilk by Saccharomyces cerevisiae EC-1118 was conducted for 48 h under static conditions with 0.15% of L-methionine, 0.10% of yeast extract, initial medium pH of 5.5, and temperature of 25°C, yielding 190 ppm of methionol. GC-olfactometry dilution analysis was conducted on extracts of the fermented soymilk, and no single compound was found to account for the overall odor perception. Methional (3-methylthio-1-propanal) and methionol were determined to be most potent odor-active compounds in the fermented soymilk. The fermented soy milk may serve as a complex sulfur flavor concentrate for applications in foods such as fermented soy products, enzyme-modified, and imitation cheeses.