I've been thinking about trying a "all natural" BOMM using a fruit in place of K2CO3 and nutrients. Some of this is due to me wanting to include more fruit as well as learning that folks have difficulty obtaining nutrients in other parts if the world. I will try to go with what I assume to be easy to obtain everywhere, but I will list all options in the hope something will be useful to others. (Especially the brave minority that wish to try Durian in mead; if you do this, please post a meadlog!)
I've monitored the BOMM enough that I have a good kinetic analysis of the gravity drop to determine if things are going as well as chemically supplemented batches. Here is the research I have so far:
Most fruit that has potassium also has bicarbonate or other pH buffering negatively charged ions. Here is the rundown of high potassium fruits and how many grams of potassium per cup of fruit:
1. Dried apricots - 1.5 grams
2. Dried prunes - 1.4 grams
3. Dried currants - 1.3 grams
4. Dates - 1 gram (167 mg/date)
5. Dried figs - 1 gram
6. Dried coconut - 1 gram
7. Avocado - 1 gram
8. Bananna - 0.8 grams
9. Kiwi - 0.55 grams
10. Nectarines or Peaches - 0.28 grams
Durian clocks in at 1.1 grams per cup, but I doubt anyone would want a raw sewage mead! I want a meadlog and pictures to prove me wrong!
Plantains have 0.93 grams per cup.
Oranges have 0.328 grams per cup.
1 tsp K2CO3 is ~4.5 grams. Also, 80% of that weight is potassium. I add 1/4 tsp three times to a 1 gallon BOMM, so that works out to 2.7 grams of potassium.
Using the info above, I can work out how much fruit to add.
Fermaid K Replacement
What is in Fermaid K? According to the manufacturer:
inorganic nitrogen (DAP), magnesium sulfate, thiamine, folic acid, niacin, biotin, calcium pantothenate, and inactivated yeast.
Exact weight of each of these is likely proprietary, but one could guess DAP, yeast hulls, and magnesium sulfate are the majority of the weight. Fermaid K is ~1 gram per 1/4 tsp which I add a total of 3 times. We can assume upfront addition with fruit will be fine due to slow extraction rates. Some guess work is invoked here. If it works, I guessed right!
Fruit High in Magnesium
Bananas - 41 mg
Dried Fruit - Figs, Apricots, Prunes, Dates, and Raisins. - ~100 mg
Fruit High in YAN
(Yeast Assimilable Nitrogen)
This is more difficult to find, but the overall consensus seems to be grape skins, orange peels, and fruit skins in general. Basically, if you use a healthy amount of fruit, you are probably fine on this.
Trace Vitamin Replacement
There is a lot of overlap in the fruit from above lists but here is the best breakdown I can find:
Thiamin (Vitamin B1) - Pineapple, Oranges, & Rosemary
Folic Acid - Bananas, Oranges, & avocado.
Niacin - Dried and frozen peaches & nectarines.
Biotin - Most fruit is rich in biotin.
Pantothenic Acid - Oranges, Figs, Watermelon, & Advocado
Calcium - Dried fruit, much overlap with the K2CO3 list.
Thankfully, there is much overlap between the lists above. Many fruits will serve as multi-purpose. This list suddenly makes the JAOM recipe make a lot of sense as well. Raisins and a whole orange will pretty much cover your bases.
For my first try at this, I'm going with dried apricots, frozen peaches, and an orange (peels and fruit, no pith). Possibly a banana thrown in for good measure. All organic as pesticides make mead taste terrible (personal experience speaking here).
NOTE: Check all dried fruit for sulfur dioxide! This will prevent fermentation at high concentration!