Isolation And Identity Of Produced-aroma Yeasts And Analysis Of Aroma Components For Fermenting 'Ya Li' Wine

1362 yeasts strains isolated successfully were from earth of garden of Hebei province, others were got from breeds of fruits and their skin were found from market.By screening four grades,we got one that was produced-aroma strain and suited to fermente 'Ya Li'pear wine,which was named Y-5.Y-5 was isolated from soil of pear garden . It is primarily identified as Saccharomyces cerevisiae by further testing biophysiological and biochemical characters.The result showed that the strain could endure the alcohol concentration of 18%,the pH value of 1.1 and the SO₂ concentration of 400 mg/L.In addition,they can ferment in the limit of sugar concentration of 75%.It had a good flocculent property with a Burnstest value of 3.6 ml.The strain grew best at 36℃ and pH 4.5,whereas it's optimum fermentation temperature and pH was respectively 30℃ and 4.5.The result of test shew that the growth and fermentation circumstances referred two effect facters temperature and initial inoculation concentration. Optimum fermentation parameters of brewing processing we got based on orthogonal test about the strain. It was proved that the proper parameters of the strain were as follows: fermentation temperature, 25℃;concentration of yeast, 1 X 107 cfu/mL;primitive pH value, 4.0;Primitive sugar concentration of 150g/L.In the conditions above referred to, the 'Ya Li'pear wine fermented by Y-5 strain was better than other strains. Thus;Y-5 strain owns the typical character of the fruit aroma produced.Aroma components of 'Ya Li' Pear Wine were the most important factors to its quality and typification. The analysis of aroma components of 'Ya Li' Pear wine provided a consultant data for its production. We took the solvent extraction to extract these aroma components of Y — 5 Yeast brewed products. According to the analysis of gas chromatography/mass spectrometry,36 peaks were separated and 35 components were identified. Thereinto, main components were accordingly Benzene ethanol;1-Pentanol;Butanedioic acid,monoethyl ester;4-(2-Hydroxyethyl)phenol;Dibutyl phthalate;Methyl 4-hydroxybutanoate;Octacosane;3-Methylthio-1-propanol;Succinic acid, Diethyl ester(Butanedioic acid,diethyl ester),etc. the amount of Benzene and 4-(2-Hydroxyethyl)phenol (52.49%) is higher than the amount in the 'Ya Li' Pear wine brewed from the vive dry yeast (29.84%) obviously. The amount of all kinds of the aromacomponents -. sense threshold and their reciprocity together decided the character of aroma of' Ya Li' pear wine.By comparing with the ' Ya Li'Pear wine brewed from active dry yeast, 'Ya Li' pear wine output brewed from Y-5 yeast was higher than other strain and its aroma was typical. Therefore,the Y-5 yeast strain is more favorable to brewe ' Ya Li' Pear Wine.