Multi-Analysis Characterization of Makgeolli Made from the Novel Glutinous Rice Cultivar ' Gureumchal': Free Amino Acids, GC-MS Volatiles, and Electronic Tongue-Derived Flavor Profile

Abstract

This study evaluated the suitability of a new glutinous rice cultivar of Gureumchal as a raw material for Makgeolli, a traditional Korean rice wine, by comparing Makgeolli produced from Gureumchal with those made from a non-glutinous rice and another glutinous rice cultivar. Makgeolli was prepared using single and blended rice combinations, and their physicochemical characteristics, amino acids, volatile aromatic compounds, and E-tongue were analyzed. The Gureumchal produced generally higher levels of total amino acids and ester compounds, particularly fruity esters, when compared with the other rice formulations. A volatile aromatic compound analysis indicated that non-glutinous rice favored the formation of acetate esters typically associated with the acetyl-CoA pathway, whereas Gureumchal produced higher levels of fruity acyl-CoA-derived esters, such as ethyl hexanoate and ethyl octanoate. An E-tongue analysis further demonstrated that rice type strongly shaped the Makgeolli's taste profile: glutinous rice samples, including Gureumchal, exhibited higher sweetness but low umami, whereas non-glutinous rice produced higher acidity and umami. Blended samples confirmed that manipulating the proportion of glutinous and non-glutinous rice allows the systematic adjustment of taste balance. Overall, Gureumchal formed a distinct flavor profile characterized by fruity esters and pronounced sweetness, indicating its potential to diversify Makgeolli quality and support targeted flavor design.

Keywords: E-tongue; Makgeolli; free amino acids; glutinous rice; volatile aromatic compounds.

Figure 1

Heatmap of free amino acid contents in different Makgeolli made from different rice cultivars and cultivar blends.

Figure 2

Heatmap showing the concentrations (mg/L) of volatile aromatic compounds in Makgeolli made using different rice cultivars and cultivar blends.

Figure 3

Biplot of variable loadings and principal component scores from the principal component analysis of volatile aromatic compounds. Numbers represent specific compounds: 1, ethyl acetate; 2, isobutyl acetate; 3, ethyl butanoate; 4, isoamyl acetate; 5, ethyl hexanoate; 6, ethyl octanoate; 7, ethyl nonanoate; 8, ethyl decanoate; 9, isoamyl heptanoate; 10, 2-phenylethyl acetate; 11, ethyl dodecanoate; 12, ethyl hexadecanoate; 13, 1-propanol; 14, isobutanol; 15, isoamyl alcohol; 16, 2-phenylethanol; 17, acetal; 18, heptanal; and 19, 5-ethenyl-2-methoxypheonol.

Figure 4

E-tongue-derived taste intensity measurements for Makgeolli made from different rice cultivars and cultivar blends. Radial scale indicates taste intensity (0–9). AHS for sourness-related; CTS for saltiness-related; NMS for umami-related; ANS for sweetness-related; SCS for bitterness-related, with two reference electrodes, a PKS and CPS. Sample names were defined by cultivar composition (w/w): C100 (100% Baekjinju, non-glutinous), G100 (100% Gureumchal, glutinous), B100 (100% Baegokchal, glutinous), C60G40 (60% Baekjinju + 40% Gureumchal, w/w), and C80G20 (80% Baekjinju + 20% Gureumchal, w/w).