Effects of pH and Temperature on the Carbonyls and Aromas Produced in Heated Amino Acid‐Sugar Mixtures

Abstract

SUMMARY: Solutions of glycine, glutamic acid, lysine, methionine, and phenylalanine adjusted to pH 6.5 were reacted separately with glucose, fructose, maltose, and sucrose at 100 and 180°C. Some of the aromas generated were reminiscent of foods, whereas others were distinctly unpleasant. Ethanal, propanal, acetone, isobutanal, aerolein, butanal, 2‐butanone, 2,3‐butane‐dione, erotanal, 2‐pentanone, and heptanal were identified as end products in one or more of the 20 mixtures. The glutamic acid‐glucose mixture was also heated at 100 and 180°C after being adjusted to pH 5.0 and 8.0. Of the compounds above, isobutanal and heptanal were not formed. Pentaual was formed at 100° but not at 180°C. A synthetic potato medium containing glucose and glutamic acid heated at 100°C yielded ethanal, propanal, acetone, butanal, 2‐butanone, 2,3‐butanedione, and crotonal. A potato extract heated at 180° differed from the synthetic potato medium heated at 100° in the products formed. Not formed were 2‐butanone and 2,3‐butauedione; pentanal, heptanal and hexen‐l‐al were formed. In all, 85 carbonyls were detected in the various mixtures or substrates.