Spectrophotometric Profiles of Off-Flavor Aldehydes by Using Their Reactions with 2-Thiobarbituric Acid

Abstract

The reaction of flavor aldehydes with 2-thiobarbituric acid (TBA) and the factors affecting this reaction have been studied. The formation rate of the 530−532 nm absorption band for detecting food rancidity through the TBA assay was dependent on the type of aldehyde and the reaction conditions. TBA reacted slowly with alkanals, and the yellow pigment (450 nm) was formed. Only after 1 h of heating at 100 °C was the red pigment formed. With 2-alkenals the reaction rate was more favorable for the red adduct (530−532 nm) formation, especially in excess TBA reagent and by employing an adequate heating time at 100 °C (water bath). For 2,4-dienals the orange pigment (494 nm) formation prevailed; the formation of the red adduct underwent a slow development (5 h at least). The development of the red adduct was favorable in an acetic acid concentration of 15−25% v/v. The yellow pigment was the only one that developed (although slowly) in glacial acetic acid medium. Keywords: Aldehydes; flavor; rancidity; 2-thiobarbituric acid (TBA)−aldehyde pigments; 2-thiobarbituric acid (TBA) assay