Discovery And Origin Of One Kind Of Earthy-mouldy Off-flavors In Chinese Liquors

The earthy-mouldy off-flavor, one of the most common off-flavors in Chinese liquor, is highly detrimental to the aromatic quality of Chinese liquor. In this paper, the nature of the characteristic earthy-mouldy off-flavor found in Chinese liquor is studied. The evolvement of the off-flavor during the process of liquor brewing is analyzed extensively. On the basis of that, the origin of the off-flavor is interpreted in order to control it effectively in Chinese liquor.1) Discovery and ConfirmationThe extraction and fractionation of liquors marked by this odor showed after analysis by gas chromatography-olfactometry (GC–O) a unique strong odorous zone having the same odor as the one perceived at tasting. The compound responsible for this odorous zone was identified by gas chromatography-mass spectrometry as TDMTD. Identification consisting of spiking stardard, sensory evaluation RI and dual column was applied to make sure that TDMTD was responsibility for earthy-mouldy off-flavor in Chinese liquor. After that, the olfactory perception threshold of TDMTD in 46%vol hydroalcoholic solution was determined as 0.11μg/L, analogous in Chinese liquor.2) Forming ProcessA rapid and simple method was developed using headspace (HS) solid-phase microextraction (SPME)-gas chromatography (GC)-electron impact (EI) mass spectrometry (MS) for quantifying TDMTD in Chinese liquor. The method displayed good linearity (R2>0.999) over the concentration ranges explored in Chinese liquor. The repeatability and accuracy of the method were also satisfying. The compound was quantified in the liquors below its olfactory threshold of perception. The concentrations of TDMTD ultrasonic extraced by water from Daqu and fermented grain were determined by HS-SPME-GC-MS as well.An quantitatively study was performed to investigate the origin of TDMTD during the process of liquor brewing. It suggests that microorganisms that develop in Daqu are responsible for the presence of TDMTD in Chinese liquor.Two strains of fungi isolated from Daqu which had the ability to produce the identified compounds, TDMTD, were identified as Emericella rugulosa and Trichoderma atroviride by combining morphological classification with molecular identification means (rDNA-ITS sequence analysis).