Maturation Mechanism Of Chinese Distilled Spirits And Its Application

Chinese distilled spirits play a superior role in alcoholic beverages, due to her ancient history and unique appearance, aroma and taste. However, fresh Chinese distilled spirits have a strong fresh spirit scent, and a pungent, bitter and puckery taste. Thereupon, it is necessary for freshly distilled spirits to store for1to several years or even decades, in order to decrease the fresh spirit scent and improve the aged taste. In this aging period, tremendous economy loss was resulted from the instrument investment,2%(V/V) spirit loss per year and massive storage of spirits. Thus obviously, for commercial profit, a variety of methods were used to accelerate the aging process as well as shorten the storage time. Nevertheless, most of existing technologies are in the empirical form due to general lacks of understanding on the maturation mechanism of Chinese distilled spirits. Hence, it is very important to deepen the maturation mechanism of Chinese distilled spirits for making some breakthrough in maturation technologies.Associative behavior of hydrogen bonding and various physicochemical parameter changes of Fenjiu during its traditional aging course from0to30years were investigated systematically. Based on the results of these experiments, the traditional maturation mechanism of Chinese distilled spirits was put forward, and a novel alternative method, which imitated the traditional aging process, was developed.The thesis includes four aspects as follows.In the first section, effects of ethanol content, age time and trace components in Fenjiu on the viscosity and fluorescence spectrum of ethanol-water mixtures were thoroughly studied. At the same time, effects of ethanol content and age time on the viscosity and fluorescence spectrum of Fenjiu were also investigated. The results show that the strength of the ethanol-water hydrogen bonding as well as the total hydrogen bonding in aged Fenjiu were predominated by ethanol content but not aging time. And strengths of these two kinds of hydrogen bonding are also influenced by trace components in Fenjiu.In the second part, changes of the content of ethanol, aroma and metal ions, and of the value of pH, electric conductivity, viscosity and fluorescence intensity, were systematically examined for Fenjiu during its30years traditional aging. The results show that with prolong of aging time, the ethanol content and pH decrease gradually, the values of electric conductivity, viscosity and metal content increase continuously, and the fluorescence intensity has no obvious trend. While the aromas contents showed diversity changes, in which the contents of ethyl acetate and lactate increase first and then decrease, contrarily to the decrease first and then increase of acetic acid, alcohols contents change slightly, and for aldehydes, the content of low-boiling ones decrease while that of high-boiling ones increase.In the third section, the maturation mechanism of Chinese distilled spirits was studied based on hydrogen bonding behaviors, various physicochemical parameters changes and three-dimensional fluorescence spectra of Fenjiu during its traditional aging. It was found that the maturation of Chinese distilled spirits is affected by a variety of factors, including evaporative loss of low-boiling-point compounds, oxidation related to dissolved oxygen, equilibrium of esterification-hydrolysis, weak interactions between moleculars, and permeation of active metal ions from the surface of ceramic containers. The conclusion goes beyond each of exsisting theories, such as "association theory","esterification theory", etc.In the fourth section, by imitating the traditional aging course of Fenjiu, the effect on its maturation of high-gravity field generated by a rotating packed bed (RPB) reactor was investigated. To determine the optimum condition, experiments were performed to examine the effects of spirit flow rate, spirit temperature and gas flow rate on the sensory score of treated spirits. Meanwhile, comparisons of each parameter were made between the treated and untreated samples. The optimum experimental condition was found to be at a spirit flow rate of80L/h, with a spirit temperature of45℃and gas flow rate of900L/h. Under this optimal condition, the treated spirit obtained a quality equivalent to that of a spirit conventionally aged for two years. Results show that the RPB treatment aged Fenjiu much faster than did conventional aging, with similar quality. Thus, RPB treatment is a potential alternative method for aging alcoholic beverages made from various materials.