Wednesday, February 13, 2013

Preparation for Vintage 2013

The main pre-vintage task is to get all the equipment clean as well as check out the integrity of some components. The acid environment of the wine making process can be harsh on tank seals, piping, gaskets and plastic airlocks
This includes the crusher, fermenter, basket press, tanks and even the picking baskets and shears.
While we cleaned up thoroughly after last vintage, a year's (and in our case 2 year's) dirt and grime can build up and everything needs to be pulled apart and done again.
It is absolutely critical to have good winery cleanliness and sanitation as dirty equipment does nothing but invite unwanted bacteria and yeasts to spoil the wine.
There are three important words used for getting equipment ready for clean winemaking.
The terms cleaning, sanitizing and sterilizing are used interchangeably.
But all three mean very different things.
Cleaning refers to the physical removal of visible dirt, grunge and old wine deposits. This is usually done with a hose with a jet spray, scrubbing brushes, scouring pads and old towels plus lots of detergent and elbow grease.
Sanitizing means doing something to equipment to reduce the microbial load to an acceptable level ie. killing spoilage microorganisms with heat or a chemical solution.
Sterilizing is another step altogether and one that goes beyond the scope of anything that can be done practically in a winery environment ie. making it completely free of bacteria or other microorganisms.
Sanitizing takes place just before equipment use.

The most common sanitizing solution used in small wineries is a strong sulphite solution.
I usually dissolve 3g potassium metabisulphite and 12g of citric acid in 4L of water. This yields about a  500 ppm solution of sulphur dioxide (SO2) which is very effective as most wine spoilage microbes are sensitive to it at this concentration.
The acid addition essentially makes the sulfur dioxide more effective ie. the SO2 consists of molecular (unionised) sulphur dioxide, the bisulphite anion and the sulphite anion with the proportions of these depending mainly on the pH.
Molecular SO2 is the most germicidal.
The more acid the solution,  the higher the proportion of molecular sulphur dioxide.
All the physically clean surfaces are rinsed well, let dry and then sprayed with the sulfur/citric acid solution. After it has been in contact for about 5 to 10 minutes the surfaces are rinsed again with clean water.
And then we are ready to go.

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