Synergistic food flavoring with red jujube extracts and caramel through the Maillard reaction

The sweet aromas of red jujube extracts and caramel products are similar, and their reactions could bring synergistic flavors. However, the reaction conditions and the characteristic flavor compounds involved are not well known. In this study, the Maillard reaction was performed using red jujube extracts and glucose caramel products. The reaction factors, such as reaction temperature, reaction time, initial pH, and sample-to-solvent ratio, were optimized by the analysis of sensory scores, total flavor compound (TFC) content, and UV absorption at 420 nm. The optimization of the above factors was further performed by response surface methodology, and antioxidant activities were investigated. Single-factor optimization suggested that the preferred conditions for the Maillard reaction were a temperature of 120°C, a reaction duration of 80 min, an initial pH of 8.0, and a sample-to-solvent ratio of 7:1 (jujube extract: caramel product = 7:1). According to the response surface model, the influence of four factors on the TFC content decreased in the following order: reaction temperature > reaction time > sample-to-solvent ratio > initial pH. The optimal conditions were further established according to the response surface model. GC-MS analysis suggested that the TFC content of Maillard products under the optimized conditions increased by 30.8% compared with those of the unreacted samples. The characteristic flavor compounds in the Maillard products were furfuryl alcohol, 3,5-dihydroxy-2-methyl-4H-pyran-4-one (DDMP), and 5-hydroxymethylfurfural (5-HMF), with the contents of 44.68, 176.26, and 139.75 µg/g, respectively. Moreover, the reaction products exhibited potent antioxidant effects.