Abstract: To clarify the quality characteristics of natural dry red wine from the Eastern Foothill of Helan Mountain, the physicochemical indexes, flavor substances and sensory profile of naturally fermented ‘Merlot’ dry red wines produced at three different regions in the Eastern Foothill of Helan Mountain were analyzed. The results showed that there was no significant difference in the basic oenological parameters such as alcohol content, residual sugar, dry extract, total acid, or pH between the naturally fermented wine and that prepared by the traditional process, while the former had lower contents of glycerol and malic acid and higher amounts of volatile acids and lactic acid. The concentrations of total phenols, tannins and anthocyanins were relatively lower in the naturally fermented wine, and the chroma and red hue were weaker, whereas the yellow hue and hue angle were not significantly different from those of the traditional one. The total amount of aroma compounds and the contents of esters of medium- and short-chain fatty acids in the natural wine were lower than those in the traditional one, while the proportions of higher alcohols, long-chain fatty acid esters with more than ten carbon atoms and phenols were slightly higher in the natural wine. Moreover, clustering analysis on aromatic components clearly distinguished the natural wine from the traditional one. In terms of olfactory properties, the chroma of the natural wine was slightly weaker, but no significant difference in taste was found. Despite having weaker fruity aroma, the natural wine had more complex flavors such as almond-like, pepper-like and vanilla-like aromas and had a higher overall score. In summary, the natural dry red wine has more prominent sensory quality and a unique style.

Key words: naturally fermented wine; Eastern foothill of Helan Mountain; Merlot; quality characteristics; gas chromatography-mass spectrometry