Defects of Wine and its Control
Wine making is work of precision. If the wine gets contaminated or it get spoiled it cannot be sold in market and it can cause a huge economic loss to the industry. Defects caused in the wine may cause change in flavour of wine, odour of wine or may cause turbidity in wine. Defects of wine may be a result of improper winemaking as well as poor storage conditions, unhygienic condition .
Defective wine is produced due to different types of defects and these defects are caused due to
- Defects caused due to micro-organisms.
- Defects caused due to non-microbial factors.
1] Defects caused due to micro-organism
Defects caused by micro-organism are also called as wine diseases. The defects are caused by two types of microorganism and that are aerobic micro-organism and anaerobic micro-organisms.
a] Defects caused due aerobic micro-organism – The organism that are capable of tolerating the alcohol content of wine can only survive and spoil the wine. The two microbes aerobic micro-organism that are capable to survive in wine are Candida mycoderma, Acetobacter.
- Candida mycoderma – Defect caused by Candida mycoderma is also called as wine flower defect. If he wine gets contaminated by this defect in presence of oxygen it causes formation of thin film and pellicle growth. Defect caused by this micro-organism affects the appearance of wine and decreases alcohol content of wine.
- Acetobacter– Acetobacter causes defect of wine by producing acid by oxidation of wine. In the defect caused by Acetobacter the wine becomes turbid as well as it gives a sour taste to the wine.
b] Defects caused due to anaerobic micro-organism– The major defect caused by anaerobic micro-organism is called as a Tourne disease. Tourne disease is a major disease if the wine gets affected by this disease then the wine is unrecoverable and it should be thrown.
- Symptoms of Disease – Increase in volatile acid content of wine is one of the symptom. The other symptom is decrease in acidic level of wine, occurrence of silky of cloudiness. It also cause mousy odour and flavour.
- Prevention of Disease – All fermentation tank should be sterilized properly. Proper hygiene and cleanliness should be maintained in industries.
- Control of Disease – Tourne disease can be controlled in the beginning as soon as the symptoms are noticed by Settling and clarification of wine by using bentonite. It can also be controlled by passing the wine through bacteriological filter and the filtered wine should be treated with 75 ppm of sulphur dioxide.
2] Defects of wine caused due to non-microbial factors.
These defects caused in wine are due to non- microbial agents like
1. Metals – Metal responsible for causing defect in wine is iron. If iron comes in contact with fermentation tank or fermentation media then this defect is caused. The ferrous ion get s oxidised to ferric ion and due to presence of ferric ion in wine two defects are caused and they are.
- Black/ Blue/ Grey/ Ferric case :- In this type of defect black, blue, grey turbidity is formed in the wine. This turbidity is caused due to reaction of ferric ion with tannin.
- White ferric case :- If the wine gets contaminated by iron in high proportion it results in reaction with phosphate and Iron phosphate precipitate is formed. The precipitate formed is of white colour so it is called as white ferric case.
2. Enzyme – The grape juice contains oxidase enzyme. If due to some reason the amount of oxidase enzyme increases then the colour of wine changes to brown.