Pasteurizing the must before fermentation can be omitted to preserve the fruit’s natural flavor. Some flavors degrade or evaporate during the heat process. The alternative way to kill contaminants is the use of sodium metabisulfite solution. It is mixed to the must. It kills almost all microorganisms except the yeast responsible for conversion of sugar to alcohol.
Sodium metabisulfite use in food applications is discouraged. The substance is under ban in many countries. It has the chance to cause allergic reaction to some sensitive persons.
Use in wine is allowed cause its purpose is not as preservative. It acts as processing aid and never became a part of final product. The substance is loss through the course of fermentation.
In a laboratory, chemical solutions like this are place in a reagent bottle – a thick glass with a glass cap. Glass is inert so reaction to its content is not possible.
I have no reagent bottle at home so I placed mine in a metal capped jar. After a year, I got the solution from cabinet and was surprised. The metal cap was totally broken. It has a big hole on center. Sodium metabisulfite reacted to rubber seal and metal. It resulted to rust and falling of metal pieces.
Experience is really the best teacher. I will never do this thing again.
I need to make a new solution!