Aroma-active compounds of wild rice (Zizania palustris L.)

Wild rice (Zizania palustris L.), an aquatic cereal grain, is gaining in popularity among consumers due to its unique nutty, roasted flavor. This study assessed the volatile chemistry of cooked wild rice to determine the odor-active compounds using a dynamic headspace system with Tenax trap, gas chromatography-mass spectrometry (GC-MS), GC-olfactometry (GC-O), and descriptive sensory analysis. Traditional brown rice (Oryza saliva L) was used to contrast with wild rice. Seventy-one volatile compounds were identified by GC-MS; six accounted for 50.2% of the total relative concentration of volatiles. A complex mixture of 33 odor-active compounds was identified by GC-O with nutty and roasted being the dominant aroma notes. Primary contributors to the unique nutty, roasted aroma were benzaldehyde, 2-n-butylfuran, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-6-methylpyrazine, 3-ethyl-2,5-dimethylpyrazine, furfural, methylpyrazine, and 2-pentylfuran. Descriptive sensory analysis illustrated the distinct aroma differences between brown and wild rice in that brown rice was primarily described as having 'cooked-rice' and 'buttery' aroma attributes and wild rice as 'nutty', 'smoky', 'hay-like', 'earthy', and 'green'. The fermentation and parching steps in the processing of wild rice appear to create the unique nutty, roasted aroma of cooked wild rice. The data provide the foundation upon which wild rice product chemistry and consumer preference can be integrated and used to optimize critical processing steps and select for progeny with superior flavor in wild rice breeding programs. (C) 2013 Elsevier Ltd. All rights reserved.