We left off last article describing the use of acid blend in wine making. Today, in our second part of a 3 part series, we’ll cover yeast nutrient, grape tannin, and Campden tablets.
Yeast Nutrient
This product contains nitrogen compounds which stimulate yeast reproduction. A healthy reproduction cycle for yeast is necessary to complete fermentations and avoid situations where fermentation becomes "stuck" – which is when a fermentation ends prior to the intended level of dryness. Too much nitrogen in your wine can also be a problem – the reproduction of yeast may become too active and create scarcity in other nutrients required by yeast. A correct balance of yeast nutrient is required – adding too much or too little will both have negative consequences. Sulfure can be released in either case (too much or too little nitrogen) and give a bad smell and taste. Fusel alcohols (off tastes) may also be formed if there is too much a yeast nutrient, instead of glycerol and trehalose which add to the texture of your wine. Therefore it is important to add yeast nutrients in your wine making, while making sure you are not over-saturating your must. Most recipies will include an amount of yeast nutrient for your home made wines, and its important to not exceed the recommended amount.
Grape Tannin
Tannin occurs in plants and is found primarily in the stems and skins of the fruits/berries. Its presence provides the pucker-mouth and bitter sensation from a wine. Tannins also provide a natural preservative. Grapes contain much more tannin than most other fruit. Young wines accentuate the tannin in a wine – as such wines higher in tannin content will benefit the most from aging. As a wine ages, the tannins will combine into long chains and add complex taste elements to the wine. This is crucial for tha ageability of a wine. So while a high tannin wine might seem overly bitter when young, it will give the wine good aging potential. Wines low in tannin are better for drinking without aging as they don’t need the time to allow the polymerization of the tannins.
Campden Tablets
Potassium metabisulphite is used in wines to kill unwanted bacteria and wild yeast. It’s also a good way of making sure no fruit fly eggs remain on the skins. Campden tablets provide a home wine or beer maker an easy method of measuring the small amounts of sulphites required for brewing. These small amounts are enough to eliminate the bacterian and wild yeast you don’t want, without altering the taste. A misconception about Campden tablets is that they will also stop fermentation. This is because while the small amount of potassium sulphite one uses is enough to slow/stall fermenation once active, it will commence again given sufficient fermentable sugars. The amount of sulphite required to completely kill the yeast would render the wine undrinkable. It is only with potassium sorbate in addition to potassium metabisulphite that the fermentation can be ended.
That’s it for today, we’ll return shortly with our next installment: pectic enzyme and wine yeast.