Impact Of Yeast Strain On The Quality Of Apple Icewine And Hawthorn Wine

Apple and hawthorn resources are rich in China. For their properties of rich nutrition and strong health functions, apple and hawthorn have been applied to control some diseases. In recent years, intensive processing of apple and hawthorn fruit has been encouraged by the Chinese government. It is not only conducive to the consumption and the industrial value of apple and hawthorn, but also in accordance with the policies of wine industry development. As one of the most promising products, apple icewine production is growing. Thus, it was deemed important to investigate the effects of different yeast strains on apple icewines. The fermentation properties of five commercial wine yeast strains were investigated and evaluated from the aspects of residual sugar, pH value, titratable acidity, organic acid, volatile compounds, and flavour. Hawthorn wine normally had higher methanol content because of high pectin content and native pectin methylesterase activity in hawthorn fruit. So we studied the measures to decrease methanol content of hawthorn wine, and evaluated the wines’ characteristics. In addition, the clarifier of hawthorn wine was studied to improve clarification and stability of hawthorn wine.1. Yeast strains play a major role on the characteristics of apple icewine. Red Fuji apple fruit in China is characterized by moderate sugar, lower titratable acidity and higher pH value. In this paper five commercial wine yeast strains, four Saccharomyces cerevisiae SIHA3 and LALVIN 71 B, K1, and R-HST and one Saccharomyces bayanus LALVIN EC1118 were applied to ferment Red Fuji apple icewine(RFAI), respectively from Red Fuji apple cryo-concentrate(RFAC). The RFAIs’ characteristics, included physical and chemical indexes, sugar and organic acid compositions, volatile substances, and organoleptic characteristic, were investigated. It was found that the indexes were significantly influenced by the yeasts applied. RFAI-EC1118 was characterized by the highest alcohol and titratable acidity, RFAI-3 by the highest total sugar and the lowest alcohol and pH value, RFAI-71 B by the highest volatile acidity and pH value, and RFAI-R-HST by the highest glycerol and total phenolics and 4.90 g/L sucrose remained. All the yeasts possessed similar capacity to metabolize mannose and decompose sucrose(except R-HST); while they did not utilize xylose. The yeast EC1118 possessed super sugar fermentation capability because it exhibited excellent ability to utilize both glucose and fructose. In addition, EC1118 had excellent organic acid production ability and the resulted RFAI-EC1118 displayed the highest content in malic, citric, tartaric, pyruvic and lactic acids, moderate in succinic and acetic acids and lowest in fumaric acid. While 71 B possessed super degradation capacity of malic acid followed by R-HST, SIHA 3 and K1, which was not suitable for such a lower acidity RFAC. There were 30 volatile substances identified and quantified in RFAIs by GC method. However, only seven components whose content exceeded the odour activity value of wine, which included 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate(only in RFAI-EC1118), ethyl butyrate, isoamyl acetate, and ethyl caprylate. Combined with the sensory analysis, EC1118 was identified as the most suitable strain for RFAI production with full-bodied and complex aromas, and followed by 71 B. EC1118 was most suitable for producing the RFAI from lower acidity Fuji apple, while 71 B was most suitable for RFAI from higher acidity Fuji apple.2. In this paper, the effect of heating temperature on the PME activity of hawthorn was determined and the measures to decrease methanol content of hawthorn wine, including raw material pretreatment, yeast strains selection and fermentation temperature, were investigated.It was found that the PME activity increased gradually from 0- 55 oC and then declined sharply from 55 oC to 80 oC. Low temperature fermentation(10 oC) could not effectively reduce the methanol content of the resulted wine. Yeast strains influenced sensory characteristic of hawthorn wine; however, they could not effectively decrease methanol content of the wine. It was indicated that heating hawthorn fruits before alcoholic fermentation significantly reduced the methanol content of hawthorn wines. Upon the ratio of material to aqueous solution of sugar 1:1.5, heating temperature 75 oC and time 10 min,hawthorn wine was provided with lower methanol content and excellent quality characteristics.3. The orthogonal test was implemented, and gelatin, bentonite, egg white and oak powder were selected as the four factors to clarify the wines, their influences on wines were evaluated. In addition, the stability texts were also implemented. The clarity of the wines was improved slightly, the luminousness value changed from 93.8% to 95.7%- 97.9%. The wines’ turbidity value, color density and tonality value and viscosity value dropped in varied extent. The stability of hawthorn wine was improved significantly with the compound clarifier. Based on overall consideration, the optimum formulation of four factors were gelatin concentration of 100 mg/L, bentonite concentration of 2000 mg/L, egg white concentration of 1%, and oak podwer concentration of 2000 mg/L.