jagmanvdp said:
Just to clarify: I don't think i am step feeding per say. T he juice (pear juice) I add later on has a SG of 1.08 so the final alcohol content of the mead (melomel) will not be greater. It will be the same..only more volume. I could add the pear juice at the beginning, but I wanted more of the flavour to last. Perhaps my reasoning is flawed.
You are in fact adding more fermentables for the yeast to work on, so if your yeast are not completely dead it is very likely (especially with D47) that they will kick up again as soon as more fermentable sugar is introduced. Your original gravity was not sufficiently high for D47 to reach its ABV tolerance and die off. If you don't want a secondary fermentation to kick up you will need to take measures to ensure that the yeast are no longer active (cold crashing and racking, sulfiting and sorbating, or filtration) or they will kick up again. They will produce fusels because they are having to deal with a change in osmotic pressure due to the introduction of fresh fermentable sugars and the other favorable components from the juice that will promote fermentation (proteins, enzymes, etc.). This causes the yeast to become stressed and it is that stress that will cause the production of reductive characters such as H2S, SO4 and fusels. Even if you add the juice during fermentation you are changing the osmotic pressure and density of the sugar and protein gradient of the must, and again this affects the osmotic pressure and causes the yeast to stress with the same results as above. I just make it a point not to step feed or introduce additional fermentables once the fermentation has begun. There is some additional very good information within the Patrons Brewlog Section posted by WayneB and others who ran some test batches similar, but much higher gravity than what we're talking about here. I don't know that the fusel production will be terrible at the ABV you are going to be working with so at a lower ABV it may be less noticeable and take less time to age. But, like I always say,
Take a chance . . . Custer did!
jagmanvdp said:
Anyways, I think I will end up with an alcohol content of roughly 10%. I picture it as fermenting the honey most of the way and then fermenting the pear. I could do them in separate containers and end up with the same thing..combining them at the end..to get my final volume.
Notable is that when you add the pear juice there will be a short time during which the yeast adjust and begin to ferment the new sugars (this is mostly when the yeast stress occurs) in earnest. But, they don't ferment in a linear fashion finishing one source and then moving on to the next. Some yeast will die, some will mutate, some will continue to ferment the honey and then whatever they can find, some will start in immediately on the pear juice. Without homogeneity of the liquid gradient they will look for the most likely target and go for it, or succumb to the change in pressure and die, or adapt and mutate.
jagmanvdp said:
And yes, i do rehydrate the yeast in water with Go-ferm. I heat the water/Go Ferm mixture to 104 F and drop the yeast in. It then sits ofr 15 minutes and then I add some of the must to start the feeding frenzy. i often build that yeast up to about 2 cups by gradually adding must to it over a few hours or more and then add that to the main primary fementor. The gradual build up of yeast also gives it a chance to cool down slowly to the same temperature as the must in the primary.
I don't know if you have the process from Lallemand or not, but your initial water temperature before adding the GO-Ferm should be 111o F. The additional mass of the GF will help to drop the temperature down to 104o F which is the point at which you should stir your yeast in slowly to ensure there are no clumps. From that point you should let it stand covered with a sanitized cloth or cotton for 15 minutes, stir, and allow to stand for 10 minutes more. You should not let it rehydrate for more than 30 minutes total as the micronutrients in both the GF and the ADY (active dry yeast) will be expended by that time and the yeast will begin to starve or feed on themselves. After the last stir, and the additional 10 minutes of waiting it's a good practice to add some of your must to the rehydrated yeast at a rate of 1/2 the volume of your rehydration slurry. So for example, if you have a 100 ml rehydration slurry you would add 50 ml of must and give it another 10 minutes before inoculating the rest of your batch with the activated and rehydrated yeast.
jagmanvdp said:
Thanks in advance!
Darren
Happy to help, I'm being granular here because a lot of newbees read this area and it's important that they know how to rehydrate the Lallemand/Lalvin yeast properly, as well as gain some insight into how yeast are adversely affected by changes in osmotic pressure and gradient density.
Hope that wasn't overkill,
Cheers,
Oskaar