Studies On The Immobilization Of Kiwifruit Wine Yeast

To immobilize the fermentation of yeast improves the separation of products from the ontology and realizes successive fermentation. In this paper, the immobilization of kiwifruit wine yeast was studied.2/3 malt juice and 1/3 juice were selected as the growth mediu for kiwifruit yeast to sieve kiwifruit yeast 1450 as the immobilized yeast.The techniques and materials of immobilization of kiwifruit yeast 1450 were studied in the experiments. The experiments selected sodium alginate and the composite of sodium alginate and polyvinyl alcohol as carriers and studied their immobilization conditions, taking the shape of bead, the coefficient of relative expansion, the dissolving time of sodium lemon and strains contained as analytical targets. The cross linking agent of carrier sodium alginate was determined as 0.2 MCaCL2, its density 2.5%; while that of the composite was 4%CaCL2, and its components were 2% sodium alginate and 6% PVA.In contrast with the fermentation abilities, the time for use, the stabilities for storage and the results through the observation of the electron micrograph scanning, the composite of 2% sodium alginate and 6% PVA was determined as the immobilized carrier. The fermentation speed of the bead from this composite was 90g/L.d; afterlS times of using, the strains dropped at 1. 2% and after 36 days of storing, the strains dropped at 16.7%. The electron micrograph showed their inner structure became looser, which was favorable for the growth and multiplication of the microorganism.Analyzes of the impacts of temperature, pH, initial sugar content, and fillings on the fermentation of the immobilized yeast suggested the following facts.The fermentation speed and conversion rate increases with the increase of the temperature when the temperature is below 22℃ while above 22℃,the fermentation was restrained. The fermentation speed increased and the sugar content drops with the increase of pH when pH is below 3.5 and the reverse comes true when pH is above 3.5 owing to the influence of the miscellaneous bacteria. The fermentation speed increases with the increase of the sugar content when the initial sugar content is below250g/L, especially between 150g/L-250g/L while when the initial sugar content is above 250g/l, the fermentation speed drops because the higher osmotic pressure by higher density restrains the fermentation of the immobilized yeast; and the fermentation speed keeps slower and the spirit content keeps higher when fillings are below 0.4g/mL while above 0.4g/mL, come the reverse. Through the experiments, the optimum temperature, pH, the initial sugar degree and the fillings were concluded as 22℃, 3.3, 250g/L, and 0.4g/ml respectively. In this condition, the fermentation speed of the immobilized yeast is three times as fast as that of the free yeast and the spirit content increases by 0.5 time, among which 68 percent Vc is preserved.The fermentation cycle covers three days by applying immobilized kiwifruit yeast into fermenting kiwifruit juice. In the wine, the total acid amounts to 8.048 g/L, the volatile acid 0.31 g/L, the alcohol degree 16% v/v, the Vc preserved 68%, and the transparency 83.6%. The wine appears light-yellow and crystal, smells fragrant, and tastes smooth.