Study On The Influencing Factors Of Fusel Oil’s Formation In Jujube Brandy

Fusel oil are important contributors to the fermentation bouquet of wine, it isproduced in the process of alcoholic fermentation of yeast metabolite.Fermentation processconditions have an important influence on the accumulation of fusel oil. Assimilablenitrogen are the nitrogen that easily assimilabed by the yeast, insufficient assimilablenitrogen results in lower biomass yields and consequently slower fermentation rates, whichincrease the risk of slow or stuck fermentations. Supplementation of musts with aminoacids and inorganic nitrogen can decrease such risks and may also affect the formation offusel oil. Fermentation process conditions and addition of assimilable nitrogen are the mainfactors that effect the formation of the fusel oil.The affect of fermentation conditions and the additioning of the assimilable nitrogento the musts on the fusel oil formation during jujube brandy fermentation were studied bysignal-factor experiment with jujube of FuPing and special yeast Saccharomyces cerevisiaeas the main materials in the paper. Main conclusions about the studies:1. Detection of fusel oil with capillary gas chromatography method were studied andthe chromatographic separation conditions were optimized, A method of simultaneousdetermination of n-propanol, iso-butanol, iso-amyl alcohol and active amyl alcohol contentin Chinese Jujube Brandy with capillary gas chromatography was established. The resultsshowed that: n-propanol, iso-butanol, iso-amyl alcohol and active amyl alcohol wereseparated well with capillary chromatographic column GC-35MS(30m×0.25mm×0.5um). The correlation coefficients of the calibration curves varied in range from0.9994to0.9997%; the recovery was97.69～102.29%, this method was in high sensitivity andaccuracy and it can be used in the detection of the main fusel oil in jujube brandy.2. The influences of fermentation process conditions on the formation of the fusel oilin jujube brandy was tested. The results showed that: yeast strains had significantlydifferent affect on the formation of the fusel oil, indicating that the ability to generate fuseloil was different from yeast strains.The formation of fusel oil increases with the yeastinoculum、fermented mash pH value and fermented mash Brix increase; fusel oil contentincreases with ethanol generaling during primary fermentation; the content of fusel oildecreased after protease treatment. However, each of these factors had no significantdifference on the percentage of each fusel oil. Different fermentation processes affect the rate of formation of fusel oil in brandy dates, but did not change the metabolic pathway offusel oil. The formation of the fusel oil in jujube brandy can be controled by selectingappropriate fermentation conditions.3.The effect of the addition of different assimilable nitrogen to the jujube must on theformation of fusel oil in jujube brandy was studied. The results showed that the formationof fusel oil was directly proportional to the quantity of isoleucine, leucine, valine,threonine and the mixed amino acids (leucine, isoleucine, valine,phenylalanine andthreonine)added to the must the while the fusel oil was inversely proportional to theaddition of the inorganic nitrogen and arginine.The effect of the addition of different aminoacids and inorganic nitrogen had different influence on the content of each fusel oil. Thefusel oil had no inconsistent trends after the adding of the different kinds of assimilablenitrogen, thus causing a change in the percentage of each fusel oil. The formation of thefusel oil and the percentage of each fusel oil in jujube brandy can be controled by addingdifferent assimilable nitrogen.