[Comparison of infrared spectra of native and esterified beer yeast]

The native beer yeast and esterified beer yeast were examined by infrared spectroscopy. The IR spectrum of beer yeast is mainly composed of the adsorption of carbohydrates, protein, etc. The dominating bands near 1652, 1532 and 1240 cm(-1) were assigned to amide I, amide II and amide III, and the characteristic IR absorption of protein could be one of the significant components of cell walls. The peak near 1 454 cm(-1) is attributable to the bending stretching of CH2- and CH3-. A substantial portion of the absorbance at 1160 cm(-1) is attributable to the stretching vibration of C-O on the structure of carbohydrates, the main components of the cell walls. The band present at 1080 cm(-1) was caused by the C-O stretching of carbohydrates and alcohols found in the RNA, the DNA and/or the cell envelop of the yeast. The peaks at 1744 cm(-1) (attributed to the carboxylate stretching) and 1454 cm(-1) confirmed the esterification process of carboxylate groups presented in the cell wall. After esterification with methanol-chloride hydride, the major components and the structures of the biomaterial remained intact.