Study On Factors Influencing The Fusel Oil In Liquor Of By Solid Fermentation

With many varieties and a long history, Chinese liquor is one of the six famous distillate liquors in the world. The manufacturing techniques of Chinese liquor are more complicated than those of distillate liquors in other countries, and even the Chinese liquors boast different styles from each other. There are various trace components in Chinese liquor, of which aliphatic acid, aliphatic ester and fusel oil are the three most important aromatic elements.As a mixture with high boiling point and a crystal liquid with colors from primrose yellow to brown, fusel oil is the general term of monohydric alcohols with more than three carbons, and is one of the important elements contributing to the flavors of liquor. However, if there are excessive fusel oils in liquor, it will be harmful to the health. The effect of poisoning and narcotism that fusel oil has are more serious than alcohol, and it makes nervous systems congest thus to make people feel headachy. It is also one of the main sources to bitterness and acerbity of liquor. Fusel oil can be formed through the two paths of degradation metabolism and anabolism in the liquor's brewing.In the experiment mentioned in this paper, fusel oil in the liquor is measured using gas chromatogram method. And the method is methodologically validated and improved.This paper mainly dealed with the factors influencing the formation of fusel oil in liquor during solid fermentation and the impact on the formation of fusel oil by adding different dosages of proteinase, saccharifying enzyme, dry yeast and amylase under the original manufacturing conditions or by changing the dosage of Daqu used in the original manufacturing conditions. The result indicated that increasing the dosage of Daqu could effectively reduce the formation of fusel oil, and adding appropriate proteinase, saccharifying enzyme and dry yeast could reduce the formation of fusel oil with effects decreasing in turn. But adding amylase had little influence on the constitution of fusel oil. In addition to the above experiments, the complex factor experiment was made and a set of manufacturing condition for generating less fusel oil was preliminarily obtained. The manufacturing conditions were 10% of the dosage of Daqu, 1% of the addition of dry yeast, 1×10~3u/g of saccharifying enzyme and 25u/g of proteinase. In other words, fermenting power, saccharifying power and protein-catabolizing were 1.03u/g, 1010.68u/g, 47.81u/g. The yield of fusel oil reduced 58%.Also in this paper, an optimal design experiment was further undertaken by applying SAS software to different dosages of Daqu and adding different dosage of proteinase, saccharifying enzyme, dry yeast and amylase. A conclusion was reached that as all various factors jointly play their roles, the dosages of Daqu and proteinase had prominent impact on the formation of fusel oil, while adding saccharifying enzyme and dry yeast had less great effect on the generation of fusel oil, but adding the amylase couldbarely influence the formation of fusel oil. At last, the orthogonal test with three factors and three levels on the dosages of proteinase, saccharifying enzyme and dry yeast was carried out based on the 10% of the dosage of Daqu, by which the manufacturing conditions for generating a small quantity of fusel oil was obtained. The manufacturing conditions were 10% of the dosage of Daqu, 0.5% of the addition of dry yeast, lx103u/g of saccharifying enzyme and 20u/g of proteinase. In other words, fermenting power, saccharifying power and protein-catabolizing were O.55u/g, 1010.68u/g, 42.8 lu/g. The formation quantity of fusel oil reduced 48%. The research showed that when the proportion between fermenting power, saccharifying power and protein-catabolizing power was harmonic in manufacturing solid liquor, less fusel oils were formed.