title: Isomers and homologues of L-glutamic acid 5-n-butyl ester as promoters of sediment formation in raw soy sauce.
abstract: Soy sauce was found to contain promoters of sediment formation at 60 degrees C, one of which has previously been identified as L-glutamic acid 5-n-butyl ester. Isomers and homologues of L-glutamic acid 5-n-butyl ester (n-propyl, isopropyl, n-butyl, isobutyl, and sec-butyl esters of L-glutamic acid) were synthesized using 80% (w/w) sulfuric acid as a catalyst and identified by 1H-NMR and the ninhydrin test. The yields of L-glutamic acid 5-n-propyl, isopropyl, n-butyl, isobutyl, and sec-butyl esters from 10 g L-glutamic acid were 25, 101, 72, 130, and 134 micromol, respectively. For maximum sediment formation in 1 ml soy sauce, 1.2, 8.6, 22.0, 22.0, and 26.5 micromol/ml of n-butyl, n-propyl, isobutyl, sec-butyl, and isopropyl esters were respectively required. Sediment-forming activity was not observed with L-glutamic acid and L-glutamic acid 5-methyl, ethyl and tert-butyl esters.
authors.affiliation: Tohoku Women's Junior College, Hirosaki, Aomori 036-8503, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tomita
authors.forename: Y
authors.initials: Y
authors.lastname: Motomura
authors.forename: H
authors.initials: H
authors.lastname: Kitahara
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshiki
authors.forename: K
authors.initials: K
authors.lastname: Okubo