Effect of rainfall and altitude on the 2-acetyl-1-pyrroline and volatile compounds profile of black glutinous rice (Thai upland rice)

BACKGROUND
The aroma intensity of rice is mixed of more than 100 volatile compounds. Fragrant rice is famous in Thailand due to specific aroma. One important volatile compound that contributes to aromatic intensity and represents a characteristic compound for fragrant rice is 2-acetyl-1-pyrroline (2AP). The production of volatile compounds and 2AP in rice is affected by various environmental factors, such as cultivation area, water content and temperature.
RESULTS
Our research employed 29 samples of fragrant colored rice (Luempua black glutinous rice cultivar) from Phetchabun province, Thailand from three harvested rice seasons (2015-2017). The cultivation areas of rice samples exhibited differences in rainfall (976.6-1260.5 mm y r−1) and altitude (26.26-1033.41 m). All volatile compounds and 2AP were identified by gas chromatography-mass spectrometry (GC-MS). In 29 rice samples, 2AP levels decreased with increasing of rainfall. The increase in altitude seems to increase 2AP levels, but some high-altitude cultivation areas resulted in low 2AP content. A variety of volatile compounds was observed in 29 rice samples from different cultivation areas. The results showed that differences in altitude and rainfall affected the production of volatile compounds in fragrant colored rice. Moreover, our results indicated that different environmental conditions in cultivation areas potentially affect volatile compound production during rice growth.
CONCLUSION
The increase in 2AP levels under low rainfall conditions and the assortment of volatile compound varieties produced in colored rice grown in different cultivation areas may be useful information for rice cultivation management striving to produce rice with high aromatic intensities. © 2021 Society of Chemical Industry.