Organic nutrients and restarting fermentation

[Thomas Christie]

Hi all,

This is my first time posting to the group, I’ve been following discussions here for a little bit and you all make for such an invaluable cider making resource. 

I’m looking for some advice on restarting a stalled fermentation in a cider I aim to bottle with some residual sugar. 

This batch was pressed on 10/17 and spontaneously fermented with an initial gravity of 1.07. After a couple of rackings and a couple of months, the gravity was down to 1.030 and progressing at about 100 FSU at an ambient temp of 55f. In a desperate effort to slow the fermentation, I added a small dose of kieselsol and chitosan before cold crashing and racking. This apparently worked better than I expected, the cider was as a result quite clear but also seemed to have stalled. After a couple weeks of no airlock activity and no measurable change in gravity while being kept in my apartment at 65f I decided to try adding some nutrients to restart fermentation.

I tried to follow Claude’s recommendation from his book of a 25ppm DAP addition for a 10 point drop in gravity, however I only have organic nutrients (FermaidO) and so tried a dosage that would make for an addition of 5 “YAN equivilants”, as organic nutrients are supposedly 3-4 times more efficient than inorganic nitrogen. Within a few days there was renewed airlock activity, but within a week this activity had stopped, with an apparent drop of ~1 or 2 points of gravity (I’m waiting on my precision hydrometer so measurement is difficult). In roughly a week since then there’s been no measurable change in gravity. 

Does anyone have experience using controlled doses of organic nutrients like this? Should I just get some DAP and follow Claude’s dosage? I’d really like to be able to bottle this pet nat for an incomplete fermentation in bottle and resulting residual sugar. Thank’s for any advice! 

-Tom Christie 

[Claude Jolicoeur]

Be patient... After a nutrient addition, it takes at least a month to really see that something is happening. A precision hydrometer will help. 

However, no I don't believe that organic nutrients would be 3-4 times more efficient by weight. Where did you get that information from?

As far as I know, most organic nutrients are from dead yeast cells that contain about 10% Nitrogen by weight, while DAP contains about 20% Nitrogen - thus making DAP twice more efficient than the organic stuff at equal weight... But this is theoretical, and would need to be tested.

[Thomas Christie]

Hi Claude,

I suspected patience may be the answer here… 

3-4 times more efficient is the claim from the manufacturer, and the idea is more efficient by nitrogen content rather than by weight. For this reason they suggest dosages according to “YAN equivalents”. So for example if you wanted a dosage of nutrients equivalent to 100ppm YAN as provided by DAP, they suggest a FermaidO dosage that actually contains only 33ppm measurable YAN. 

The claim is that nitrogen provided by amino acids is more efficient for fulfilling cell metabolic needs than that provided by ammonia, the analogy I’ve seen is that inorganic nitrogen is like “candy”, yeast assimilate it quickly and sprint through some fermentation for awhile before crashing and needing further additions to continue fermenting. Meanwhile organic nitrogen is the “balanced diet”, leading to slower and steadier fermentation. 

It’s just occurred to me that there may also be an issue here of assimilation in the presence of ethanol, I think it might be that organic nitrogen uptake is inhibited at higher levels and that could also be a problem for me. So perhaps I’ll give it a month to watch for any change and meanwhile get myself some DAP to dose according to your suggestions. 

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