Reference

Investigation of pyrazine formation pathways in glucose-ammonia model systems

Investigation of pyrazine formation pathways in glucose-ammonia model systems. Shibamoto, Takayuki; Bernhard, Richard A. (Dep. Food Sci. Technol., Univ. California, Davis, Calif., USA). Agric. Biol. Chem., 41(1), 143-53 (English) 1977. CODEN: ABCHA6. DOCUMENT TYPE: Journal CA Section: 17 (Foods) Model systems of D-glucose [50-99-7] and NH3 with metal ions, oxygen, antioxidants, and NaOH were reacted at 100.degree. (soln. temp.) for 2.apprx.18 h to investigate pyrazine [290-37-9] formation pathways. Pyrazines identified in these model systems were unsubstituted-, 2-methylpyrazine [109-08-0], 2,5-dimethylpyrazine [123-32-0], 2,6-dimethylpyrazine [108-50-9], 2-ethylpyrazine [13925-00-3], 2,3-dimethylpyrazine [5910-89-4], 2-ethyl-5-methylpyrazine [13360-64-0], 2-ethyl-6-methylpyrazine [13925-03-6], 2,3,5-trimethylpyrazine [14667-55-1], 2-ethyl-3-methylpyrazine [15707-23-0], 2-vinylpyrazine [4177-16-6], 2-ethyl-3,5-methypyrazine [13925-07-0], 2-ethyl-3,6-dimethylpyrazine [13360-65-1], and ethylvinylpyrazine [59094-70-1]. Results show that .alpha.Several substances with their cas registry numbers 108-50-9 and 109-08-0 may be metioned in this study.-amino carbonyl compds. acted as intermediates to form various pyrazines. For example, 2-methylpyrazine may be formed from the condensation of .alpha.-amino-.alpha.-hydroxy acetaldehyde [62163-52-4] and .alpha.-amino acetone [298-08-8] following the elimination of a water mol. It was proposed that the formation of a pyrazine ring from dihydropyrazine was due to the dehydration of hydroxy dihydropyrazine rather than the dehydrogenation of dihydropyrazine. This explains the formation of an alkyl group (e.g., an E group) from the sugar moiety. Ten .alpha.-amino carbonyl intermediates were proposed from the alkylpyrazines which were obtained, and their formation schemes were discussed. .

Changes in aroma components of green tea during the firing process

Changes in aroma components of green tea during the firing process. Hara, Toshio; Kubota, Etsuro (Natl. Res. Inst. Tea, Shizuoka 428, Japan). Nippon Nogei Kagaku Kaishi, 58(1), 25-30 (Japanese) 1984. CODEN: NNKKAA. DOCUMENT TYPE: Journal CA Section: 17 (Food and Feed Chemistry) Volatile compds.Some commonly used reagents like 141-79-7 and 78-70-6 are used in this experiment. of green teas fired in a firing machine at 130° for 10, 20, and 30 min were prepd. by vacuum distn. and analyzed by gas chromatog. (GC) and GC-mass spectrometry for comparison with volatile compds. of nonfired green tea (raw tea). The major aroma compds. of raw tea decreased slightly during the firing process. The off-flavor compds. found in stored green tea decreased markedly during the firing process. Pyrazines, pyrroles, furans, 3,7-dimethyl-1,5,7-octatriene-3-ol [29957-43-5], and phenylacetaldehyde [122-78-1] were produced during firing. Methylpyrazine [109-08-0], 2,5-dimethylpyrazine [123-32-0], 1-ethylpyrrole-2-aldehyde [2167-14-8], 2-acetylpyrrole [1072-83-9], and furfural [98-01-1] increased markedly after firing for 30 min, and these pyrazines and pyrroles might be important volatiles in the formation of fired tea flavor. The amts. of 3,7-dimethyl-1,5,7-octatriene-3-ol and phenylacetaldehyde were higher in fired low-grade tea compared with high- and medium-grade tea. .