ABSTRACT
Aroma is one of the diagnostic aspects of rice quality that determines the acceptance or rejection of rice before it is tested (Verma et al., 2012, 2013, 2015). It is also considered as an important property of rice that indicates its preferable high quality and price in the market (Paule and Powers, 1989; Ishitani and Fushimi, 1994). Early research on rice aroma can be traced 30 years back (Buttery et al., 1982, 1983), but more scientific progress in modern analytical techniques has been achieved with the discovery, development, and application of gas chromatography. Gas chromatography received tremendous advances and innovations when combined with mass spectrometry to form the technique known as gas chromatography-mass spectrometry (GC-MS). This technique made identification and quantification of volatile compounds much easier in mixtures of sample matrix and greatly enhanced interest in chemistry of rice aroma. An assessment of all known data reveals that more than 500 compounds have been documented in various aromatic and non-aromatic rice cultivars (Table 1.1) (Widjaja et al., 1996a; Verma and Srivastav, 2016). The primary goals were to identify the compounds responsible for the characteristic rice aroma (Buttery et al., 1982). Many attempts are made to date to search the key compounds for rice aroma (Buttery et al., 1982, 1983), but any single compound or group of compounds that are fully responsible for rice aroma have not yet been reported. The first volatile aroma compound, 2-acetyl-1-pyrroline (2-AP), was reported in 1982 by Buttery et al. (1982) and discovered by Buttery et al. (1983) in 1983 from aromatic rice due to its strong volatile characteristic. 2-AP is the most important flavoring compound of cooked rice since its discovery (Buttery et al., 1982, 1983). Rice consists of balanced complicated mixtures of volatile aroma compounds that impart their characteristic flavor. There are no single analytical techniques that can be used for investigation of volatile aroma compounds in rice sample. Although, currently, many technologies are available for the extraction of rice volatile aroma compounds and these technologies have been also modified time-to-time according to the need, many of them are still under process to emerge into a new form, particularly in the distillation and extraction concept.
