After the Laboratory Class, Students Should Be Able To

BOT 323 Industrial Microbiology

Fruit wine production

Introduction

Wine is an alcoholic beverage made from grape juice with an alcoholic content between 8-15% (v/v). Alcoholic beverages that are made from other kinds of fruits are commonly called fruit wine. To achieve high alcoholic content, fruit juice must have sugar between 20 to 25 oBrix. Sometime sugar (sucrose) is added to raise level of sugar content. In addition, nitrogen compounds such as ammonium sulfate or diammonium phosphate must be also supplemented (1 g/L) to prevent stuck fermentation. Prior to inoculate yeast starter culture (Saccharomyces cerevisiae), indigenous microorganisms is eliminated by addition of SO2 in the form of sodium metabisulfite at 200 ppm. In theory, sodium metabisulfite contains 58% of SO2.The juice should be allowed to stand for at least 3 hours before yeast inoculation. Then, the fermentation is commonly carried out in an open container or a closed container with an air lock device. The fermentation should take place at around 20-25 oC. High fermentation temperature promotes production of higher alcohols. After finish alcoholic fermentation, fruit wine should be clarified by mean of finning and filtration, then, bottling.

Objective

After the laboratory class, students should be able to:

1. Produce wine and fruit wine

2. Explain the principle of alcoholic fermentation

Materials and Methods

Materials 1. Saccharomyces cerevisiae 2. Fruit juice 3. Potassium metabisulfite 4. Diammonium phosphate 5. Sugar 6. Hand refractometer 7. Distillation unit 8. Burette 9. Erlenmeyer flask 10. pH meter 11. Chemical for determining free SO2 using ripper method

Methods 1. Measure oBrix and pH of fruit juice 2. Adjust sugar level to 22 oBrix and Add diammonium phosphate at 1 g/L

3. Adding potassium metabisulfite to make 200 ppm of free SO2 then measure free SO2 using ripper method

4. Leave the juice for 3 hours (covered) then measure free SO2 using ripper method again

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5. Add yeast to the juice and mixed with a glass rod that is previously sterile with 70% ethanol 6. Pour the mixture into a plastic bag 7. Cut the hole at the top of plastic bag and connect with a 1000 L pipette tip using a rubber band (the end of the pipette tip extend out from the plastic bag 8. Cover the end of plastic pipette tip with cotton tighten with a rubber band o 9. Incubate for 7 days at room temperature then measure Brix, pH, free SO2, alcoholic content

Determination of free SO2 using ripper method 1. Add 25 mL of wine into an Erlenmeyer flask (125 mL) 2. Add 1 mL of soluble starch 3. Add 5 mL of sulfuric acid (1 part sulfuric acid + 3 part water) and titrate with 0.02 N iodine solution immediately until turn into blue color for at least 30 second

4. Calculate free SO2 concentration

Determination of alcoholic content using an alcohol meter 1. Distill 30 mL of wine sample (100 mL) 2. Adjust the volume of distillate back to 100 Ml 3. Pour the reconstitute alcoholic solution into a 100 mL measuring cylinder 4. Put the alcohol meter into the measuring cylinder and read the value of alcohol (The reading should be read at 20oC for accuracy)

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