Comparison of aromatic compounds in jasmine rice of different origin

Bc. Aneta Kašíková

Master's thesis

Abstract:

Rice is a staple food for the vast majority of people around the world and the different cultures have preferences for various types of rice. Aromatic varieties have special characteristics such as a distinctive and attractive aroma resulting from a complex mixture of volatile substances. Their aroma is therefore the most valuable factor in determining quality and price. The characteristic high intensity odour of aromatic rice comes mainly from a compound 2-acetyl-1-pyrroline (2AP), described as the aroma of popcorn or pandan with an extremely low threshold. The solid phase microextraction was used for the extraction of volatile compounds from Thai jasmine rice. The optimised conditions for SPME were 1 g sample of ground rice in a 4 ml vial, sampling temperature at 80 °C for 30 min and exposure of the polydimethylsiloxane fibre in the headspace for 20 minutes. Identification of volatile compounds of Thai jasmine rice of different origin was performed by gas chromatography mass spectrometry and principal component analysis (PCA) was used to observe similarities in their volatile profile. A total of 59 volatile compounds were identified among the fifteen experimental samples of Thai jasmine rice. From these, 27 were identified in Thai conventional and organic jasmine rice collected in the Czech Republic, 22 in Thai conventional jasmine rice and 18 in Thai organic jasmine rice purchased in Chiang Mai region in Thailand. The volatile compounds in Thai jasmine rice were mainly aldehydes, alcohols, ketones, hydrocarbons, terpenes, and other low-volatile compounds. 2AP was found in two samples purchased in the Czech Republic and one sample collected in Thailand presented a trace amount in the chromatogram. This study found separation into the groups based on origin of the samples using PCA. Although SPME was regarded as a promising method for extraction of plant material, the methodology was not uniform, particularly in terms of extraction time and sample amount, which affected extraction efficacy. For future research, it would be appropriate to optimise SPME conditions for rice by increasing the extraction time and sample amount, which may enhance the final content of volatiles as well as focus on impact of biotic and abiotic stress in detail, in order to minimise aroma loss.

Keywords

Thailand, Oryza sativa, volatile compounds, aroma, 2-Acetyl-1-pyrroline, SPME, GC-MS

Language used: English

Date on which the thesis was submitted / produced: 23. 8. 2023

Thesis defence

• Date of defence: 19. 9. 2023
• Supervisor: Ing. Olga Leuner, Ph.D.
• Reader: Lucie Jurkaninová, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme / field:
Tropical Agriculture / Tropical Crop Management and Ecology