Really Confused about Hydrometer reading

[CatsCradle]

Hi everyone. I am relatively new to fermenting/ brewing. a couple months ago I started a 4 gallon cider fermentation and used an Omega Ale yeast. My starting gravity of the cider was 1.050 ( I used Motts). Following a couple weeks of primary fermentation I racked to secondary using four 1 gallon glass carboys. I took a hydrometer reading and it showed a 1.010. I then put in roughly 1 pound of raspberries in one carboy, 1 pound of strawberries in the second fermentor, about 3/4 cups of pomegranate juice in the third fermentor, and kept the fourth pure cider. A week went by and I decided to rack the raspberry and strawberry ciders off the fruit into new carboys. I took a quick hydrometer reading and saw that they both were 1.0004. I transferred to new carboys and topped off with some more motts apple juice to avoid excess headspace (roughly 2.5 cups each). Fast forward a couple more weeks and I decide to check my ciders again for gravity. Here is where stuff becomes super confusing. I first checked my unaltered pure cider and saw that it maintained a 1.010 gravity reading. This made sense and I was happy with it. Then I checked the pomegranate cider and saw that it too had maintained a 1.010 gravity. How is this possible I saw alot of fermentation since adding the pom wonderful juice, and the juice contains a good amount of sugar, yet no gravity alteration occurred. I then checked the raspberry cider and was completely baffled when I saw the gravity actually increased from 1.004 to 1.010 again. How is this possible? I wanted to add some more gravity so I put in 1 cup of white sugar into the raspberry and then again took a gravity reading and saw that the reading was still 1.010.

All in all I am completely baffled. Any insight would help me

 

[pvpeacock]

I don't completely understand what happened to each of the batches you describe. However, when you add fruit, sugar or more apple juice to your fermented cider, the specific gravity will go up. That new sugar will then get fermented by the yeast and lower the specific gravity again.

Just looking at your Pom Wonderful batch, if your fermented cider was 1.010 before you added Pom Wonderful juice, the specific gravity would have gone up when you added the juice. Assume this juice addition increased the specific gravity up to 1.020. This new sugar in the form of juice would then be fermented by the yeast (secondary fermentation) which would reduce the specific gravity again. Apparently, the yeast did its job and brought the specific gravity back down to 1.010.

Next time, take the specific gravity before adding sugar, fruit or apple juice and immediately after you do so. Then check again when you think secondary fermentation has stopped.

 

[CatsCradle]

I don't completely understand what happened to each of the batches you describe. However, when you add fruit, sugar or more apple juice to your fermented cider, the specific gravity will go up. That new sugar will then get fermented by the yeast and lower the specific gravity again.

Just looking at your Pom Wonderful batch, if your fermented cider was 1.010 before you added Pom Wonderful juice, the specific gravity would have gone up when you added the juice. Assume this juice addition increased the specific gravity up to 1.020. This new sugar in the form of juice would then be fermented by the yeast (secondary fermentation) which would reduce the specific gravity again. Apparently, the yeast did its job and brought the specific gravity back down to 1.010.

Next time, take the specific gravity before adding sugar, fruit or apple juice and immediately after you do so. Then check again when you think secondary fermentation has stopped.

Ok thanks so much! Quick question, how would I calculate the alcohol addition of the juice going from 1.020 to 1.010. I have read in some forums that a person shouldn't account for fruit and juice additions when calculating abv as there is a substantial amount of water along with the sugar in the fruit and or juice.

 

[palmtrees]

Ok thanks so much! Quick question, how would I calculate the alcohol addition of the juice going from 1.020 to 1.010. I have read in some forums that a person shouldn't account for fruit and juice additions when calculating abv as there is a substantial amount of water along with the sugar in the fruit and or juice.

There really isn't a way to calculate that now. You would have to know what the gravity was right after you added the juice. If you knew that, you could calculate how much of that had turned to alcohol using your FG and then you could add that amount of alcohol to the amount you knew had been produced by the initial fermentation that stopped at 1.010. In the future, take a hydrometer reading right before any additions and then another one right after you make any additions.

 

[Chalkyt]

Sorry if this gets a bit long winded, but I am intrigued. Your final SG readings don't seem quite right for what has happened, can you check them? If that sounds insulting, sorry, it isn't meant to be, but the old adage "if it ain't measured, it ain't real" always come to mind when things don't add up.

Firstly, starting at 1.050 and ending up at 1.010 after a couple of weeks seems quite possible. Then 1.004 after another week also seems O.K. if fermentation was reasonably fast. My ciders would typically go from 1.050 to 1.010 in around four weeks and can be around 1.002-1.004 after a few more weeks (my usual yeast is SO4 which can stop as high as 1.004). So far so good.

So are you sure that your 1.010 reading after what seems to be about six weeks fermentation is correct? Around 1.001 is where I would expect the cider could be by then even after adding the relatively small amount of sugar in the fruit and juice. Was anything else added that would increase the density and so throw the SG readings out of whack?

Most fruit and juice has between 5% and 10% sugar ( about the same as a teaspoon of sugar in a cup of tea or coffee). So adding a pound of fruit (about 0.5kg) and even less pomegranate juice to your gallon (say 4 litres) of cider means that you only added about 1% extra sugar... hardly enough to make any difference even though it would have generated some fermentation activity. The extra cup of sugar at the end (say 250g) should kick the sugar concentration up by around 60g/L which would add 0.020 to the SG and when fermented add about 3% ABV.

Admittedly this is only rough "back of the envelope" arithmetic on my part (and could be wrong) but unless something has happened to stall the fermentation around 1.010, you've got me stumped if your figures are correct, since it is pretty hard to stop the yeast from chewing up all the sugar and leaving the cider at 1.000.

Maybe others can suggest some insight.

 

[CatsCradle]

Sorry if this gets a bit long winded, but I am intrigued. Your final SG readings don't seem quite right for what has happened, can you check them? If that sounds insulting, sorry, it isn't meant to be, but the old adage "if it ain't measured, it ain't real" always come to mind when things don't add up.

Firstly, starting at 1.050 and ending up at 1.010 after a couple of weeks seems quite possible. Then 1.004 after another week also seems O.K. if fermentation was reasonably fast. My ciders would typically go from 1.050 to 1.010 in around four weeks and can be around 1.002-1.004 after a few more weeks (my usual yeast is SO4 which can stop as high as 1.004). So far so good.

So are you sure that your 1.010 reading after what seems to be about six weeks fermentation is correct? Around 1.001 is where I would expect the cider could be by then even after adding the relatively small amount of sugar in the fruit and juice. Was anything else added that would increase the density and so throw the SG readings out of whack?

Most fruit and juice has between 5% and 10% sugar ( about the same as a teaspoon of sugar in a cup of tea or coffee). So adding a pound of fruit (about 0.5kg) and even less pomegranate juice to your gallon (say 4 litres) of cider means that you only added about 1% extra sugar... hardly enough to make any difference even though it would have generated some fermentation activity. The extra cup of sugar at the end (say 250g) should kick the sugar concentration up by around 60g/L which would add 0.020 to the SG and when fermented add about 3% ABV.

Admittedly this is only rough "back of the envelope" arithmetic on my part (and could be wrong) but unless something has happened to stall the fermentation around 1.010, you've got me stumped if your figures are correct, since it is pretty hard to stop the yeast from chewing up all the sugar and leaving the cider at 1.000.

Maybe others can suggest some insight.

Hi thanks so much for your response! yes I was completely baffled so I took the reading several times making sure that the hydrometer was in the center of the liquid in the sample vial. This was bothering me all day yesterday and I have come up with perhaps some explanations. Firstly I do think that one explanation could be the lack of yeast in my carboy. Taking my 1 gallon raspberry for example. It is currently in a third container/ fermentor and each time I had transferred I left behind absolutely massive yeast cakes. Transfer from primary to secondary left behind a large cake and then again after I racked off the fruited secondary to a third vessel. My thought is that perhaps there was not enough yeast to ferment the sugars in the apple juice, so therefore the gravity reading naturally increased a couple points. Tasting the cider it was very very sweet, almost like a commercial angry orchard. Something that is pretty interesting is that I added a pound of sugar later on to the raspberry to increase its abv strength, and after 3 days it has not should signs of fermentation. I tasted it again and it remains very sweet.

 

[Chalkyt]

You could be right. I don't know if you have read or have Claude Jolicoeur's book The New Cider Makers Handbook. He is quite a fan of multiple rackings and uses this approach to reduce the level of nutrients in the cider by leaving them behind with each racking. This reaches the point where the yeast population cannot be sustained and so fermentation slows or stops. The end result of this can be a long slow fermentation process that ends up with a medium or sweet cider once all fermentation ceases. I haven't tried this as I generally aim for a slightly sweet carbonated cider by bottling then stopping the yeast at the right point.

The book is well worth the $30-$40 or so, as it contains a wealth of information.

 

[CatsCradle]

You could be right. I don't know if you have read or have Claude Jolicoeur's book The New Cider Makers Handbook. He is quite a fan of multiple rackings and uses this approach to reduce the level of nutrients in the cider by leaving them behind with each racking. This reaches the point where the yeast population cannot be sustained and so fermentation slows or stops. The end result of this can be a long slow fermentation process that ends up with a medium or sweet cider once all fermentation ceases. I haven't tried this as I generally aim for a slightly sweet carbonated cider by bottling then stopping the yeast at the right point.

The book is well worth the $30-$40 or so, as it contains a wealth of information.

Yes sounds like a great book. So much fantastic info out there. One more thought. I added potassium metabisulfite to my must after racking off of the fruit. Can this maybe be a culprit?

 

[Chalkyt]

The short answer is "I don't know". I only use potassium metabisulphite after pressing, then leave it to dissipate for 24 hours or so before adding yeast.

Others who use it might have some idea as it could well stop the yeast and secondary fermentation.