In this study, Saccharomyces cerevisiae cells were immobilized in the apple pomace by using air-blast drying and characteristics of cider fermentation were studied by the immobilized yeast cells. Apple pomace was freeze-dried to remove moisture and then made into a powder form before use as a yeast ...
In this study, Saccharomyces cerevisiae cells were immobilized in the apple pomace by using air-blast drying and characteristics of cider fermentation were studied by the immobilized yeast cells. Apple pomace was freeze-dried to remove moisture and then made into a powder form before use as a yeast immobilization carrier. The immobilized yeast cells were dried by the air-blast drying, and used for the cider fermentation.
When the yeast cell suspension mixed with the apple pomace powder at a ratio of 1:1, 2:1, 3:1, 5:1, 10:1 (w/w) were dried by the air-blast drying, the ratio of 2:1 showed the highest survival rate. In addition, the survival rates by concentration of 0%, 5%, and 10% of skim milk were tested, which acts as an anti-freeze agent to increase the survival rate of dry yeasts. As a result, 10% skim milk showed the highest survival rate. When the mixture of 10% skim milk with fructose or sucrose at concentrations of 0%, 5%, and 10% was used as a protectant, the highest yeast viable cell count was obtained at the 5% fructose and 10% skim milk mixture. Comparing the survival rates of air-blast drying and freeze-drying after immobilizing the mixture on the apple pomace using the optimal protectant selected based on the previous results, it showed a 99% survival rate in the air-blast dried yeasts, which was higher than that of freeze-dried yeasts.
As a result of conducting an experiment to select the optimal drying time, it showed the highest survival rate (101.67%) after air-blast drying for 60 minutes, which showed a water content of 10% or more. Looking at the water content by drying time, it showed the lowest water content after drying for 105 minutes. When dried for 90 minutes which showed a higher survival rate than 105 minutes, no significant difference was observed in the water content. During the long-term storage experiment, changes in the survival rate was analyzed for 0, 15, 30, 60, and 90 days, respectively, at storage temperatures of 4°C and 20°C after air-blast drying for 60 minutes and 90 minutes. When stored at 4°C, after 90 days, the survival rates were 80.55% and 76.81% for 60 minutes and 90 minutes, respectively, which about 20% of the survival rate decreased compared to those immediately after drying. When stored at 20°C, on the other hand, the survival rate dramatically decreased after 15 days and could not be confirmed at 90 days.
Cider fermentation was carried out by using the 4 yeast samples of S. cerevisiae EC1118 free cells, S. cerevisiae W153 free cells, immobilized and dried S. cerevisiae W153 at concentrations of 0.5% and 1.0%. During the fermentation, the contents of soluble solids and reducing sugar decreased as fermentation progressed. After the fermentation was completed, the soluble solid content ranged from 7.3 to 7.4 °Brix and the reducing sugar content was 0.27 to 0.45%, showing similar concentrations in all conditions. In addition, the results of pH and total acid also showed similar values as fermentation progressed regardless of whether or not they were immobilized in all conditions. The final alcohol content was 12.03-13.06%, which is similar to the alcohol content of general fruit wine. Organic acid contents were 7.624-10.457 mg/mL, and the highest content was obtained in the malic acid. As a result of the sensory evaluation, no significant difference in all samples was observed in the sensory quality items of color, sweetness, and sourness. However, there was a significant difference in the flavor between the ciders by the free cells and the immobilized cells.
In this study, Saccharomyces cerevisiae cells were immobilized in the apple pomace by using air-blast drying and characteristics of cider fermentation were studied by the immobilized yeast cells. Apple pomace was freeze-dried to remove moisture and then made into a powder form before use as a yeast immobilization carrier. The immobilized yeast cells were dried by the air-blast drying, and used for the cider fermentation.
When the yeast cell suspension mixed with the apple pomace powder at a ratio of 1:1, 2:1, 3:1, 5:1, 10:1 (w/w) were dried by the air-blast drying, the ratio of 2:1 showed the highest survival rate. In addition, the survival rates by concentration of 0%, 5%, and 10% of skim milk were tested, which acts as an anti-freeze agent to increase the survival rate of dry yeasts. As a result, 10% skim milk showed the highest survival rate. When the mixture of 10% skim milk with fructose or sucrose at concentrations of 0%, 5%, and 10% was used as a protectant, the highest yeast viable cell count was obtained at the 5% fructose and 10% skim milk mixture. Comparing the survival rates of air-blast drying and freeze-drying after immobilizing the mixture on the apple pomace using the optimal protectant selected based on the previous results, it showed a 99% survival rate in the air-blast dried yeasts, which was higher than that of freeze-dried yeasts.
As a result of conducting an experiment to select the optimal drying time, it showed the highest survival rate (101.67%) after air-blast drying for 60 minutes, which showed a water content of 10% or more. Looking at the water content by drying time, it showed the lowest water content after drying for 105 minutes. When dried for 90 minutes which showed a higher survival rate than 105 minutes, no significant difference was observed in the water content. During the long-term storage experiment, changes in the survival rate was analyzed for 0, 15, 30, 60, and 90 days, respectively, at storage temperatures of 4°C and 20°C after air-blast drying for 60 minutes and 90 minutes. When stored at 4°C, after 90 days, the survival rates were 80.55% and 76.81% for 60 minutes and 90 minutes, respectively, which about 20% of the survival rate decreased compared to those immediately after drying. When stored at 20°C, on the other hand, the survival rate dramatically decreased after 15 days and could not be confirmed at 90 days.
Cider fermentation was carried out by using the 4 yeast samples of S. cerevisiae EC1118 free cells, S. cerevisiae W153 free cells, immobilized and dried S. cerevisiae W153 at concentrations of 0.5% and 1.0%. During the fermentation, the contents of soluble solids and reducing sugar decreased as fermentation progressed. After the fermentation was completed, the soluble solid content ranged from 7.3 to 7.4 °Brix and the reducing sugar content was 0.27 to 0.45%, showing similar concentrations in all conditions. In addition, the results of pH and total acid also showed similar values as fermentation progressed regardless of whether or not they were immobilized in all conditions. The final alcohol content was 12.03-13.06%, which is similar to the alcohol content of general fruit wine. Organic acid contents were 7.624-10.457 mg/mL, and the highest content was obtained in the malic acid. As a result of the sensory evaluation, no significant difference in all samples was observed in the sensory quality items of color, sweetness, and sourness. However, there was a significant difference in the flavor between the ciders by the free cells and the immobilized cells.
주제어
#Apple pomace Immobilization Air-blast drying Cider
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