Abstract
Aroma rice, e.g. Basmati and Jasmine rice, is very popular among rice consumers in South and South-East Asia and is becoming famous in USA and Europe. Thailand is one of the major rice exporters; rice produced from Thailand possesses peculiar properties as aroma, appearance, and texture. One outstanding property of Thai rice, known as “Jasmine rice”, is its fragrance. The characteristic flavour of this rice is principally contributed by 2-acetyl-1-pyrroline. There are many varieties of aroma rice produce in Thailand, among which Khao Dawk Mali 105 (KDLM105) variety is the most famous one.
In this experiment, we investigated volatile organic compounds (VOC) of Thai rice (Oryza sativa) by using five varieties: KDLM105, RD15, PTN1, HSP and CNT1. All of them were planted in the experimental field in 2005. The first four varieties are aroma rice, the last one is a rice variety of high yield and good grain. The Jasmine rice bought from the retail store was also used. VOC released to the head space from dry stored and moistured-heated rice were sampled using solid phase microextraction (SPME). In order to optimise the device suitability, three different fibers, Carboxen/PDMS, Carbowax/DVB and PDMS/DVB, were chosen. The resulting compounds were analysed using GC-MS. In parallel, sensory evaluation of rice samples was carried out focussing on odour perception of the panel considering the parameters “variety” and “ageing”. The majority of VOC identified as highly abundant were aldhydes. Hexanal, considered as an off odour, was detected even in recently harvested rice.