Does fermentation restart changes cider flavor?

[Kekshiukaz]

I've been fermenting 3 gallons of apple wine. Original gravity is 1.100. It was fermenting smoothly for 6 days and everything was okay. However after 6 days fermentation became very sluggish and almost stopped at 1.030. It was definitely too sweet so I added +3.5 grams of yeast nutrient and +2 grams of the same yeast. Fermentation restarted succsessfully but I'm afraid that after restart taste can become bad. Does adding more yeast and nutrients during fermentation can spoil the taste?

 

[D the Catastrophist]

Yes. And no.
The wine fermenting to a lower sg will change the taste, as will aging the wine. The yeast and nutrients shouldn't impact the flavor negatively unless you went very heavy handed.
But you need to be patient. 6 days is ridiculously short for wine making. I typically see closer to 21 days. Slow is good, it produces less off flavors.

 

[Chalkyt]

I think your numbers are O.K.

In theory you need to ferment a further 30 gravity points, so if your fermentation stalled due to lack of nutrients, you would need 10ppm of YAN (Yeast Assimilable Nitrogen) for each further 10 gravity points to be fermented. In practice this is done by adding nutrient such as DAP which is 20% YAN (i.e. 50ppm of DAP per 10 gravity points).

In your case, this is 30/10 x 0.05g DAP x 12 litres = 1.8g of DAP. Your 3.5g of nutrient is probably twice what you really needed, but these numbers can be a bit rubbery so I wouldn't expect such a smalll amount to cause any issues.

I routinely add about 1/4 teaspoon (roughly a gram) of DAP to 5 litres after primary fermentation has finished, just to ensure complete fermentation and don't have any taste/flavour issues. I do this because I often use S04 which is a high nutrient dependent ale yeast and have had ciders stall at around 1.015 if the juice is low in YAN. Juice from late season apples from old, unfertilised trees or juice that has been in cold storage for too long can be low in YAN.

The extra yeast probably wasn't needed as the population would have grown by itself and simply stopped working if it ran out of nutrient (if indeed that was the issue, but it sounds like it).

 

[Kekshiukaz]

I think your numbers are O.K.

In theory you need to ferment a further 30 gravity points, so if your fermentation stalled due to lack of nutrients, you would need 10ppm of YAN (Yeast Assimilable Nitrogen) for each further 10 gravity points to be fermented. In practice this is done by adding nutrient such as DAP which is 20% YAN (i.e. 50ppm of DAP per 10 gravity points).

In your case, this is 30/10 x 0.05g DAP x 12 litres = 1.8g of DAP. Your 3.5g of nutrient is probably twice what you really needed, but these numbers can be a bit rubbery so I wouldn't expect such a smalll amount to cause any issues.

I routinely add about 1/4 teaspoon (roughly a gram) of DAP to 5 litres after primary fermentation has finished, just to ensure complete fermentation and don't have any taste/flavour issues. I do this because I often use S04 which is a high nutrient dependent ale yeast and have had ciders stall at around 1.015 if the juice is low in YAN. Juice from late season apples from old, unfertilised trees or juice that has been in cold storage for too long can be low in YAN.

The extra yeast probably wasn't needed as the population would have grown by itself and simply stopped working if it ran out of nutrient (if indeed that was the issue, but it sounds like it).

Thank you.

 

[Chalkyt]

It also occurred to me that if you started at SG 1.100, you might have chaptalized with sugar since most apple juice would have a SG of around 1.050 (110g/L of sugar plus 20g/L of non fermentable solids) Typically "good" apples would have 80-120 ppm of YAN which should be more than enough to ferment SG 1.050. However, the inherent YAN may be insufficient to allow complete fermentation of SG 1.100 and so stalling at 1.030 because of nutrient depletion sounds plausible, especially as you say that adding nutrient has started things off again.

By the time your SG had fallen to 1.030 the ABV would be in the region of 9% - 10% which could be getting close to some beer/ale yeast's alcohol tolerance. It shouldn't be an issue with wine yeast but just something to be aware of with ale or cider yeasts since your eventual ABV might be in the order of 13% or more.

 

[Midway Island]

I've been fermenting 3 gallons of apple wine. Original gravity is 1.100. It was fermenting smoothly for 6 days and everything was okay. However after 6 days fermentation became very sluggish and almost stopped at 1.030. It was definitely too sweet so I added +3.5 grams of yeast nutrient and +2 grams of the same yeast. Fermentation restarted succsessfully but I'm afraid that after restart taste can become bad. Does adding more yeast and nutrients during fermentation can spoil the taste?

The apple flavor may be diminished, when racking I would add a 64oz. Jug of motts apple juice to the 5 gallons that will bring out the apple and balance out the dryness.