Primary Volatile Aroma Compounds in Phka Rumduol, Cambodia

Phka Rumduol is a leading variety in Cambodian rice. Analysis and qualification of volatile aroma compounds of Cambodian rice were not reported yet, limiting a few papers about only 2-acetyl-1-pyrroline (2-AP). Although Cambodia has been very impressive and progressed for milling rice exports over the last 10 years, rice qualities in her value chain are still remained much more improvement, especially in domestic market. In this paper, volatile aroma compounds in Phka Rumduol (brown rice), cultivated by Cambodian Agricultural Research and Development Institute (CARDI) was analyzed by gas chromatograph mass spectrum (GCMS) and aroma extract dilution analysis (AEDA). As the results, 2-AP and other 21 aroma compounds were detected. Its flavor dilution (FD) factor of 2-AP was extremely high at 10,000. Since 2-AP was dominant aroma in Phka Rumduol, the analytical measure of 2-AP by solid phase micro extraction (SPME) and gas chromatograph (GC) in rice kernels were investigated. With the purpose to compare qualities between Phka Rumduol (CARDI) and Phka Rumduol purchased in a Cambodian market (commercial), 2-AP concentration of both samples, the changes of 2-AP by different milling degrees, using both samples and 2-AP concentration in red kernels in commercial were analyzed. The results showed that 2-AP of Phka Rumduol (CARDI) and Phka Rumduol (commercial) were 800 and 380 ppb respectively, that after 0, 1, 2, 3 and 4 minutes-milling, the 2-AP in CARDI ranged in 800 to 420 ppb, while commercial did in 380 to 250 ppb and that 2-AP of whole red kernels in commercial was 50 ppb. From the results changes of milling time, 2-AP was located more in out-layer than inside of rice kernel. Phka Rumduol (CARDI) was very good qualities, while Phka Rumduol (commercial) showed less 2-AP concentration with larger percentages of broken, red kernels and lower qualified kernels like immature, chalky, damaged ones etc. Aroma which is one of important factors for Cambodian consumers will be decreased by rice type and grade of processing in market. This paper also referred a little to decrease in qualities by excess milling and/or polishing.