Step 1: Fermentation and Flavouring
At the beginning, you can add a clay called bentonite that will bond to positively charged proteins for increased clarity and decreased aromas. The negatively-charged bentonite will ride the CO2 bubbles created by the yeast, collecting proteins along the way. Once the bonded molecule reaches the top and the bubble bursts, it will sink back down and do the cycle over again.
The beginning is when you add flavour adjuncts like oak or elderflower to soak into the wine.
Add your wine yeast to the “must” – and wait a couple of weeks for the magic to happen. Cover your container to limit bacterial/fungal contamination.
You can usually smell the fermentation happening (the room will smell like a vineyard – another perk of the hobby!) and hear the carbonation, but if you’re concerned that no fermentation is happen, you can take a quick look. Try not to let the must be exposed to the air for too long though to avoid contamination.
Step 2: Transferring and Clearing
Now that the sugars in your wine have been converted to alcohol by the yeast, you want to clear the yeast and any of the fermentation by-products that make the wine cloudy and add off-flavours.
First sanitize your fermentation bucket, tubing and mixing utensil. Transfer wine from the carboy to the bucket while trying to keep as much of the sendimented yeast in the carboy as possible. You need to stir the wine with your utensil as much as possible for 10-15 minutes to de-gas the wine, which will aid the clearing agents.
Here’s a neat trick my barber taught me. If you want to de-gas carbon dioxide throughout the process, place your carboy on top of your dryer. The shaking motion will efficiently degas the wine.
Add sulphite to your wine. You might have noticed “contains sulphite” on commercial wine bottles. Sulfur dioxide limits oxidisation and bacterial activity. You can always skip this step if you want to go the organic route. Organic wineries omit sulphite and get a unique flavour as oxygen and bacteria go to down on breaking down the wine and producing so-called off-flavours. Wines without sulphite may go bad quickly, especially white wines since they’re low in tannins unlike red wine. Tannins also act as an anti-oxidant.
After the sulphite is well mixed into the wine, add the potassium sorbate to complete the job of limit yeast and bacteria growth. The sulphite deprives the yeast and bacteria of the oxygen they need to reproduce. Meanwhile, the sorbic acid of potassium sorbate makes the wine environment inhospitable to their growth. An added bonus of stabilizing the wine’s environment is you know the alcohol level will stay the same since the wine yeast is also inhibited from growth.
Now to add your fining agents of kieselsol (silicon dioxide) and chitosan (chitin – the exoskeleton of shell fish). These have positive and negative molecular bonds, respectively. You add the kieselsol first to bond to negatively charged molecules, mix thoroughly for a few minutes, then add the chitosan to bond to positively charged molecules, mixing thoroughly.
Step 3: Bottling
Now that your wine has cleared, you can transfer it to your bottling bucket, leaving more sendiment behind, and then into bottles for long-term storage (or not so long-term storage depending on your drinking habits). Ageing your wine will change the flavour as molecules continue to react with oxygen and rogue bacteria that escaped the fining process continue to munch down on the alcohol, turning it into vinegar ever so slowly.
Store your bottles upright for a few days for the corks to expand and seal the bottle neck. After that, store the bottles on the side to keep the cork wet. Store in the coolest, darkest place in your house to extend the wine’s shelf-life.