Contribution of roasted grains and seeds in aroma of oleang (Thai coffee drink)

Oleang, a Thai coffee drink, contained roasted robusta coffee and several roasted grains and seeds. In this research the typical ingredients of oleang that were robusta coffee, corn, soybean, rice, sesame and brown sugar, were roasted and studied for their volatile compounds. Coffee, corn, sesame, and brown sugar were roasted at 220°C for 20 min and soybean and rice were roasted at 240°C for 20 min. Major aroma compounds from roasted corn were 2-furfurylthiol, furfural, 2-methoxyphenol, hexanal, and alkylpyrazines. Soybean contributed mostly pyrazines and phenols similar to those of coffee. The roasted rice had strong sulfurous and burnt characteristics but was low in concentrations of the volatile compounds. The roasted sesame was most abundant in the numbers of aroma compounds provided dimethyl trisulfide, dimethyl disulfide, 2-furfurylthiol, 3-ethyl-2,5-dimethylpyrazine, and 2-methoxyphenol to oleang. Sixteen oleang formulations were evaluated for their sensory preference. The samples were composed of 5% brown sugar, coffee (50, 60, 70, and 80%) with various corn: soybean: rice: sesame ratios (2:3:0:0, 3:2:0:0, 3:1:1:0, and 3:1:0:1). The most preferred formulation for oleang was 50% coffee, 5% brown sugar, and 45% grain mixture that had the corn: soybean: rice: sesame ratio of 3:1:1:0.