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Starting Gravity Mismatch

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miabeewood

NewBee
Registered Member
Apr 5, 2018
10
0
0
Denver, CO
I was playing around with the calculator and noticed that the expected starting gravity for my mead was very different from the measured starting gravity. I was wondering what might cause this.

I made a 5 gallon batch with 15 lbs of honey, 6 lbs of cherries, and 1 cup of orange juice. Based on the calculator I should have a starting gravity of 1.116.
Instead, the measured starting gravity was 1.044. At the time, I didn't have a sample tube so I was measuring in the carboy, but I was careful to keep it away from the edges. I now have a sample tube, so that won't be an issue anymore.

When figuring out the alcohol content, should I assume I messed up measuring and go based on the estimated SG, or do I assume I messed up the mead and go with my measured SG?
 
D

darigoni

Got Mead? Patron
GotMead Patron
Jun 4, 2016
946
65
28
Brookline, NH
Go with the estimate. Sounds like your honey might not have been fully mixed. What are you getting for reading now?

I assume your hydrometer gives you a reading of 1.000 when you use it in water?
 
Stasis

Stasis

Honey Master
Registered Member
Jan 10, 2014
1,123
13
38
Malta
Probably undissolved honey.
Much sugar is still locked away in the cherry flesh. When you break open fruit only the sugars from the juice are unlocked but the yeast can use the sugars from the flesh as well. When making prickly pear wine were I to use just the juice I would get about 2% less abv. The calculator also only gives estimates. Your cherries could be less sweet and your orange juice could be less sweet. I also suspect that the calculator doesn't do so well with fruit.. I think it gives best case scenarios for fruit. The only way to do this calculations well is to take gravity readings of your fruit juices and adjust the %sugars in the calculator. Even honey can vary in the %sugars department. Are you sure you have EXACTLY 5 gallons of must after the additions of the cherries and the OJ?
 
D

darigoni

Got Mead? Patron
GotMead Patron
Jun 4, 2016
946
65
28
Brookline, NH
I don't think it was problem with the cherries or the amount of water. With 15 lbs of honey, it would have had to be a 12 Gallon batch to get a OG = 1.044 :)
 
Stasis

Stasis

Honey Master
Registered Member
Jan 10, 2014
1,123
13
38
Malta
darigoni said:
I don't think it was problem with the cherries or the amount of water. With 15 lbs of honey, it would have had to be a 12 Gallon batch to get a OG = 1.044 :)
Click to expand...

I was thinking maybe it was a group of reasons rather than just 1 culprit
 
M

miabeewood

NewBee
Registered Member
Apr 5, 2018
10
0
0
Denver, CO
So sounds like a general consensus that I need to do a better job mixing my must. I have a lees stirrer now, so that should be super easy. Also good to know that solid fruit may not be reflected in the initial SG. So that would need to be factored in mentally.

1 week post-pitching the measured SG was 1.016. I dumped 15g of D47, which chugged like crazy (I actually had to clean my ceiling it was foaming so hard).
 
Chevette Girl

Chevette Girl

All around BAD EXAMPLE
Moderator
Lifetime GotMead Patron
Apr 27, 2010
8,447
59
48
Ottawa, ON
It really all depends on how much of a control freak you are and when you like to add your fruit. Remember, fruit contains sugar but also a lot of water so it.s really more likely to dilute your must than strengthen it.

I always use pectinase when I use fruit and I let it sit with the fruit (or in the fruit must with the fruit) for 24 hours before I introduce the fruit to the yeast (or the yeast to the must). At that point I figure most of the juice has been released into the must and my SG should be relatively accurate.

And remember, you don't want to put whole fruit in a must anyway, you generally want to mash it to release the juices, at which point, the sugar and water are now both contributing to your SG. If it's not affecting your hydrometer, it's not going to be easy for your yeast to get to.
 
Stasis

Stasis

Honey Master
Registered Member
Jan 10, 2014
1,123
13
38
Malta
It's not only about the juice being released into the must. If I take a batch of prickly pears and I mash and strain the living daylights out of them (through a press such that the tunas become something flat and hard and dry like cardboard) I can get a hydrometer reading which indicates potential alcohol to be 4%, for example. This potential alcohol is more or less this value on multiple calculators. Were I to throw those prickly pears into a bucket, ferment them and perform a spirit indication test I get an alcohol reading of around 6%. This happens just about each year I use prickly pears.
This means that either:
- My hydrometer readings are wrong
- The calculators are wrong
- The tunas hold additional sugars in the flesh...

These sugars are never released into the must. Perhaps the pulp will even absorb sugars from your honey if you dump the tunas into the must. If I taste that dry cardboard-like disc that remains in the press after I squeeze the tunas it will taste good and sweet even without juice. If I were to press the flesh after ferment is over they will look like, feel like and taste like actual cardboard. No sweetness at all.

Let me explain this in simpler terms.
Imagine you test your must and you measure that there should be 1kg of sugars inside. You take out the tunas and press them. You're still measuring the juice so you still measure about 1kg of sugars in your must. However, were you to somehow extract the sugars from the pressed tunas there actually is 1.2kgs of sugars. During fermentation the yeast DO extract the sugars from the tunas in ways we cannot so the yeast have access to those 1.2kgs rather than the 1kg you estimated in the start. At the end of ferment you press the tunas, make a spirit indication test and you get 6% abv rather than your estimated 4%abv from the juice alone

This is why I think that taking a hydrometer reading of must with fleshy fruit inside can never be 100% accurate.
 
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