# Chemometric Approach for Discriminating the Volatile Profile of Cooked Glutinous and Normal-Amylose Rice Cultivars from Representative Japanese Production Areas Using GC × GC-TOFMS

## TL;DR

This study uses advanced chemical analysis to identify volatile compounds that distinguish the aroma of cooked glutinous and normal rice from Japan.

## Contribution

The study introduces a comprehensive volatile profile of cooked rice using GC × GC-TOFMS, revealing new compounds and flavor markers.

## Key findings

- GC × GC-TOFMS identified 1924 volatile compounds, ten times more than previous methods.
- Glutinous rice showed higher levels of ketones, furans, and thiols, contributing to sweeter and floral aromas.
- Normal rice was rich in ethers and aldehydes, associated with grainy and toasty notes.

## Abstract

Cooked-rice aroma strongly affects consumer choice, yet the chemical traits distinguishing glutinous rice from normal-amylose japonica rice remain underexplored because earlier studies targeted only a few dozen volatiles using one-dimensional gas chromatography–mass spectrometry (GC-MS). In this study, four glutinous and seven normal Japanese cultivars were cooked under identical conditions, their headspace volatiles trapped with MonoTrap and qualitatively profiled by comprehensive GC × GC-TOFMS. The two-dimensional platform resolved 1924 peaks—about ten-fold previous coverage—and, together with hierarchical clustering, PCA, heatmap visualization and volcano plots, cleanly separated the starch classes (78.3% cumulative PCA variance; Euclidean distance > 140). Volcano plots highlighted 277 compounds enriched in the glutinous cultivars and 295 in Koshihikari, including 270 compounds that were not previously documented in rice. Normal cultivars were dominated by ethers, aldehydes, amines and other nitrogenous volatiles associated with grainy, grassy and toasty notes. Glutinous cultivars showed abundant ketones, furans, carboxylic acids, thiols, steroids, nitro compounds, pyrroles and diverse hydrocarbons and aromatics, yielding sweeter, fruitier and floral accents. These results expand the volatile library for japonica rice, provide molecular markers for flavor-oriented breeding and demonstrate the power of GC × GC-TOFMS coupled with chemometrics for grain aroma research.