Effect of drying and storage times on aroma quality of Khao Dawk Mali-105 brown rice

Khao Dawk Mali-105 (KDML) is fragrant Thai rice variety which is well-known and popular in the United States and many countries in Asia and Europe. Drying and storage times are factors affecting aroma of an aroma of fragrant rice. Therefore, the aim of this study was to investigate the effect of drying and storage times on aroma quality of KDML fragrant brown rice (KBR). KBR was dried in tray dryer at 35°C for 2 and 6 hours. Then, KBR was kept in linear low density polyethylene (LLDPE) bag at the dark at room temperature for 8 months. Aroma descriptive analysis, 2-acetyl-1-pyrroline (2-AP) and hexanal content, thiobarbituric acid (TBA) value and moisture content of KBR at 0, 2, 4, 6 and 8 months were evaluated. Drying time did not significantly affect aroma characteristics of KBR. The intensity of desirable aroma such as pandan-like aroma of uncooked KBR and cooked corn-like aroma of cooked KBR decreased significantly with longer storage time. On the contrary, the intensity of undesirable odors such as rancid and musty odors significantly increased upon storage. Cooked KBR that dried at 35°C for 2 and 6 hours had higher intensity of cooked corn-like aroma and lower intensity of undesirable odors than those of non-drying treatment. The 2-AP content of KBR was decreased after drying treatment and during longer storage. The hexanal content and TBA value of KBR were significantly increased along with storage. The moisture content of KBR (12.58%) significantly decreased after drying treatment for 2 and 6 hours (10.83% and 10.25%, respectively); however, the storage time did not influence on moisture content of KBR. These results indicate that drying and storage times affect on the aroma quality of KBR. Therefore, these factors should be considered in order to maintain rice aroma quality during storage.