Volatile Aroma Compounds in Jasmine Rice as Affected by Degrees of Milling.

Abstract

Jasmine rice (Khao Dawk Mali 105) is popular because of its pleasant unique aroma. Milling is an important step in order to produce various types of edible rice. The distribution of volatile aroma compounds in rice especially, endosperm and bran fractions are different. Hence, the purpose of this study was to determine the volatile aroma compounds of low-milled and high-milled Jasmine rice that affect the aroma quality of cooked rice. The new crop of Jasmine paddy was used in this study. Volatile aroma compounds in raw and cooked rice with two degrees of milling, i.e., low-milled rice (2-4% rice bran) and high-milled rice (11-13% rice bran) were investigated. The raw and cooked samples were extracted with dichloromethane and analyzed by gas chromatography-time of flight mass spectrophotometer (GC-TOFMS). The amount of volatile aroma compounds in rice was decreased with high milling. 3-Penten-2-ol (green odor), the most abundant compound in raw rice, was the lowest amount in high-milled rice. On the other hand, the high-milled rice bran had the highest amount of this compound. After cooking, more types of volatile aroma compounds were detected. 2-Acetyl-1-pyrroline (2AP) (pandan-like, popcorn-like) was the most abundant in cooked rice. Meanwhile, hexanal was the highest amount in cooked rice bran. However, 2AP was the potent aroma compound with the highest odor activity values in both raw and cooked rice with low and high milling degree as well as in rice bran.