Electrochemical esterification in distilled liquor via gold catalysis and its application for enhancing ester aroma of low-alcohol liquor.

The development of low-alcohol liquor (Baijiu) can represent a tool to solve the problems of excessive alcohol intake. However, low-alcohol liquor has an insufficient ester aroma and a bland taste due to the alcohol dilution process. This study proposes an electrochemical catalysis technology to catalyze the esterification reaction between the acid and alcohol in liquor, thereby enhancing the ester aroma of low-alcohol liquor. In the electrochemical conversion process, the gold electrode with a certain potential promotes the formation of carbocation intermediate from corresponding carboxylic acid, thereby improving the esterification reaction efficiency. The key finding is that the total ester content of liquor treated using this technology is increased by more than 20%, and a strong ester aroma is attained. This study clarifies the electrocatalytic mechanism of the esterification reaction in liquor, and provides a new idea for making low-alcohol liquor become more attractive for aroma and taste aspects trying to obtain an alternative product contributing to the public health.

Correction to "Influence of Electrochemical Oxidation on the Maturation Process of the Distilled Spirit".

[This corrects the article DOI: 10.1021/acsomega.0c02090.].

Elucidating metal ion-regulated flavour formation mechanism in the aging process of Chinese distilled spirits (Baijiu) by electrochemistry, ICP-MS/OES, and UPLC-Q-Orbitrap-MS/MS.

Elucidating the organometallic interactions in Baijiu will promote a deeper understanding of the flavour formation mechanism during Baijiu aging. However, the organometallic interactions during aging are difficult to explore because the concentration and status of metals in Baijiu samples are affected by other substances (such as organic acids), and the concentrations of these substances also change dynamically. Hence, the flavour formation mechanism of aged Baijiu was investigated based on a multi-method analysis (i.e. electrochemistry, ICP-MS/OES, and UPLC-Q-Orbitrap-MS/MS), which enabled us to solve the difficulty above. The key finding is that, in the aging period, the organic acids induce the transformation of the metal ion state from the complex state to the free state. As a result, the flavour compound (i.e. the esters) contents in aged Baijiu are regulated by the free metal ion-catalyzed reactions.

Elucidating oxidation-based flavour formation mechanism in the aging process of Chinese distilled spirits by electrochemistry and UPLC-Q-Orbitrap-MS/MS.

The oxygen-based oxidation process is leading toward the understanding of the flavour formation mechanism of aged Baijiu. However, the oxygen-based oxidation process in Baijiu aging is difficult to explore because of (1) the composition of Baijiu produced in different batches varies a lot and (2) the spontaneous oxidation needs several years or even decades to occur. Hence, the flavour formation mechanism of Baijiu aging was investigated using electrochemistry and UPLC-Q-Orbitrap-MS/MS, which enabled us to solve the two difficulties above. The oxidation reaction on gold surface could accelerate Baijiu aging by catalyzing the transformation from alcohols to acids. Although natural aging contributed more diverse compound changes to Baijiu, the oxygen-based oxidation process during natural aging was similar to that in the electrochemical oxidation as a whole. This study provides new insights to flavour formation mechanism of aged liquors and provides a new way for liquor-related enterprises to optimise the aging process.

Mechanisms of the regulation of ester balance between oxidation and esterification in aged Baijiu.

The influence of oxidation and esterification on the ester balance of aged Baijiu and methodology for the rational design of liquor flavors to optimize the practice of Baijiu production are not completely understood. We investigated the influence of ester balance on the flavor compounds of aged Baijiu by conducting constituent analysis of Baijiu from different aging times (0, 1, 2, 3, 4, 5, and 10 years). The changes of the main flavor compounds in the aging process were determined, and the correlations among different chemical reactions, such as oxidation, hydrolysis, and esterification, were systematically expounded. Furthermore, cluster analysis of the heat map indicated significant differences between aged Baijiu and new Baijiu and recommended a suitable aging time of 2-3 years.

Influence of Electrochemical Oxidation on the Maturation Process of the Distilled Spirit.

Optimizing the aging process is urgently required in the distilled spirit industry because of the time-consuming and expensive procedure of natural aging. Herein, the componential changes of the liquor sample are confirmed by the component analysis (e.g., gas chromatograph), and the effect of electrochemical oxidization treatment on the overall properties of typical Chinese liquor (Baijiu) is investigated. The key finding is that high oxidative potential can be used to catalyze the oxidation of alcohols, and the reaction rate is dramatically faster than that in the process of natural aging. The present study reveals the influence of electrochemical oxidation on the contents of compounds (particularly, the alcohols) in Baijiu and offers a perspective into the utilization of electrochemical oxidization treatment as an alternative strategy for artificial maturation of Baijiu.