| Summary: | 碩士 === 輔仁大學 === 食品科學系碩士班 === 103 === Surplus yeast is a byproduct generated during the beer brewing process. However, studies concerning the determination of functional compounds in surplus yeast are inadequate. The objectives of this study were to determine the variety and content of prenylflavonoids and hop bitter acids in surplus yeast by using HPLC coupled with photodiode array detector (DAD) and tandem mass spectrometry. Results showed that freeze-dried surplus yeast consisted of 4.7% moisture, 49.7% crude protein, 1.0% crude fat, 4.9% ash and 39.6% carbohydrate. A total of 4 prenylflavonoids and 20 hop bitter acids could be separated simultaneously within 30 min by employing a Thermo HyPURITY C18 column (150 mm × 4.6 mm I.D., 5 μm) and a gradient solvent system of phosphoric acid in water (pH 1.6) and acetonitrile with flow rate at 1.0 mL/min, column temperature at 35oC and multiple detection wavelengths at 276, 292, 330 and 368 nm. Based on comparison of retention time, absorption and mass spectrum of flavonoid peaks with that of commercial standards and reported in the literature, the 4 flavonoids compounds were identified to be isoxanthohumol, 8-prenylnaringenin, 6-prenylnaringenin and xanthohumal, while 20 hop bitter acids to be cohulupone, hulupone, adhulupone, trans-isocohumulone, cis-isocohumulone, trans-isohumulone, cis-isohumulone, trans-isoadhumulone, cis-isoadhumulone, cohumulone, humulone, adhumulone, prehumulone, postlupulone, adprehumulone, colupulone, lupulone, adlupulone, prelupulone and adprelupulone. Isoxanthohumol was found to be the most abundant flavonoid followed by prenylnaringenin, whereas hulupone and humulone were shown to dominate among the hop bitter acids. Overall, the HPLC-DAD-MS/MS method developed in this study could effectively determine the level of flavonoids and hop bitter acids with short analysis time, good resolution, high accuracy and high precision.
|
|---|
