Quantitative analyses of 2-acetyl-1-pyrroline (2AP) and n-hexanal were analysed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) technique. The optimum condition of gas chromatograph-mass spectrometer were (1) the column temperature program started at 45 ํC upon injection and was increased at a rate 3 ํC/min to 80 ํC, then at a rate of 5 ํC/min to 120 ํC, and finally at a rate of 20 ํC/min to 180 ํC (2) the liner was SPME liner (3) the mass spectrometer was operated in full scan mode from mass per charge(m/z) 35 to 200 for the qualitative analysis and (4) SIM (selected ion monitoring) was used for the quantitative analysis. Under these operating conditions, retention time of 2AP and n-hexanal were 11.15 and 19.94 minute, respectively. SPNE-GC-MS was used to investigate 2AP and n-hexanal contents of Jao Hom Supunburi brown rice during storage for 6 months. The brown rice was coated by using its rice flour gel as the coating polymer. The coated rice and uncoated rice were packed in unbleached cloth (control), polypropylene and oriented polypropylene (OPP)/ aluminum (AI)/ linear low density polyethylene (LLDPE) bags. 2AP content decreased during storage in all packaging and rice packed in laminated bag decreased the least. Coating rice process reduced 2AP content as compared to uncoated rice. The rancid volatile, n-hexanal increased during the first two months and then slowly decreased throughout storage; rice packed in laminated bag contained less n-hexanal than the other two packagings. Coated rice with flour gel reduced n-hexanal as compared to uncoated rice. Moreover, moisture content and water activity of rice packed in PP and laminated bags increased after the first month and then remained relatively constant until 6 months. Moisture content and water activity were lower in the uncoated rice than the coated rice. Furthermore, overall preference scores (1-7) of cooked coated brown rice and uncoated brown rice stored 6 months was in the range of 3 to 4 points.
