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Single Kernel Analysis of Rice for 2-Acetyl-1-Pyrroline
C. GRIMM (1), S. Lloyd (1), R. Bryant (2). (1) SRRC-ARS-USDA, New Orleans, LA, U.S.A.; (2) DALE BUMPERS NATIONAL RICE RESEARCH CENTER, Stuttgart, AR, U.S.A.
The key odorant compound in fragrant rice, such as Jasmine and Basmati, is 2-acetyl-1-pyrroline (2AP). In non-fragrant rice, the 2-AP, although present in trace amounts does not accumulate. Mutation at one or more sites inhibits production of the enzyme BADH2 and allows 2AP to accumulate in fragrant rice. An 8 base pair deletion has been identified on chromosome 8. Methods for analyzing 2AP have continually been refined since Buttery et al, first identified 2AP as the primary odorant compound and now allow for quantization at the parts per billion ranges from samples taken from a single kernel. Single kernel analysis allows for the determination of adulteration and within-kernel variation of 2AP levels. Use of potassium hydroxide to release the 2AP from the starchy endosperm, combined with solid phase microextraction for sample preparation and analysis by gas chromatography- mass spectrometry greatly facilitate the sensitivity and ease of analysis. The SPME/KOH method recovers 50-55% of 2AP from a single kernel. The lower limit of detection is dependent upon kernel size and ranges from 20-50 ppb. A comparison of 2AP in brown vs. milled rice suggested a higher content in milled rice for that particular variety.
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