Correlation analysis between volatile compounds and α-dicarbonyl compounds in various beans in response to different roasting conditions

In this study, the content of volatile compounds and alpha-dicarbonyl compounds (alpha-DCs; glyoxal, methylglyoxal, and diacetyl) were analysed in various beans (soybeans, black soybeans, and mung beans) roasted at different times and temperatures. Among the volatile compounds detected in unroasted soybeans, 1-octen-3-ol was the most abundant. After roasting, 1-octen-3-ol decreased by up to 86%. In unroasted beans, 3-ethyl-2,5-dimethylpyrazine and 2,3,5-methylpyrazine which are the main volatile compounds after roasting were not detected. Roasting at 180 degrees C for 25 min produced the highest amount of volatile compounds. Roasting at 200 degrees C for 25 min produced the highest amount of alpha-DCs. As the roasting temperature and time increased, the level of alpha-DCs and volatile compounds showed a positive correlation (spearman correlation, r = 0.878, 0.890, and 0.867 in soybeans, black soybeans, and mung beans, respectively). Volatile compounds and colour values showed a negative correlation (spearman correlation, r = 0.917, 0.967, and 0.850 in soybeans, black soybeans, and mung beans, respectively). The results of this study suggest that the optimal roasting conditions for beans are 180 degrees C for 25 min, where the generation of flavour compounds is maximised while the generation of alpha-DCs is relatively small.