This is a bit long, but a few weeks ago when there was some discussion about the “usefulness” of the squeeze bottle test to assess carbonation, I suggested that I had trial taking place about this and would post about it. So here it is.
I normally use a test bottle and pressure gauge to monitor carbonation, however I thought it might be worthwhile comparing this approach with just using a squeeze bottle.
The issue seems to be that once a squeeze bottle is hard, there is no way of knowing what the carbonation level is beyond that. i.e. hard is hard, and extra carbonation doesn’t change it. Also, there doesn’t seem to be any way of knowing how much carbonation makes the bottle hard. If you squeeze a Coke bottle, it is hard but how much carbonation is that? Popular theory is that soft drink is carbonated to 2.5 volumes, but I have seen 3+ volumes quoted elsewhere for Coke.
To get a handle on all of this, I fully fermented a small batch of Pink Lady juice from 1.050 down to 1.000 using S04 and a pinch of DAP.
Sugar syrup was added to the fully fermented juice to bring the SG up from 1.000 to 1.010 (20g/L sugar) and the cider was bottled filling 95% of each bottle so that the air space to cider ratio was the same in each bottle. The bottles were a 500ml plastic squeeze bottle, a 500 ml glass test bottle with a pressure gauge, and several 330ml glass crown seal bottles (no sense in wasting the leftover cider). They were all kept in the cool store at 18C.
Sorry if it sounds like a high school science experiment, but really it was just making another batch of cider and recording some numbers.
Trying to quantitatively assess the hardness of the squeeze bottle wasn’t very useful. The freshly filled 70mm diameter plastic bottle squeezed about 3mm (about 4%) at the start (i.e. gauge pressure of 0 bar). As the fermentation for carbonation progressed, at gauge pressure 1.6 bar (22psi) the bottle was hard and only squeezed by1mm. So, trying to relate gauge pressure to mm of squeeze was not practical.
I found that once the gauge pressure built up to more than 1.6 bar, the “squeeze bottle had reached its maximum hardness and didn’t change with more carbonation. So, that is about as far as the squeeze bottle goes for indicating carbonation pressure.
Gauge pressure of 1.6 bar is 2.3 volumes of C02 at 18C. i.e. a pleasantly carbonated beverage. This is only 10% below the common target of 2.5 volumes carbonation for cider.
It would be reasonable to take the time it took to develop 1.6 bar of pressure and extrapolate that to determine the extra time needed to reach a higher pressure.
For those who want to follow the numbers… I let fermentation continue until gauge pressure was 1.8 bar (2.5 volumes of CO2) and did a taste test with the squeeze bottle (Yum…a nicely carbonated cider with a touch of sweetness due to the residual unfermented sugar). At this point the SG was 1.007 so about 6.5 g/L of sugar had been fermented into 1.6 volumes of CO2. So, the numbers lined up O.K. since 1.6 volumes from the fermented sugar plus typically 0.9 volumes already in solution from the original fermentation equals 2.5 volumes, and so there was about 13 grams or 2½. teaspoons (½ teaspoon per glass) of unfermented sugar left). This seemed like a good time to hot waterbath pasteurise the crown sealed bottles.
So as a reward for all this work I am now drinking the squeeze bottle as I write, and will probably drink the pressure gauge test bottle tomorrow…win-win!
Cheers! I hope this helps someone.
I normally use a test bottle and pressure gauge to monitor carbonation, however I thought it might be worthwhile comparing this approach with just using a squeeze bottle.
The issue seems to be that once a squeeze bottle is hard, there is no way of knowing what the carbonation level is beyond that. i.e. hard is hard, and extra carbonation doesn’t change it. Also, there doesn’t seem to be any way of knowing how much carbonation makes the bottle hard. If you squeeze a Coke bottle, it is hard but how much carbonation is that? Popular theory is that soft drink is carbonated to 2.5 volumes, but I have seen 3+ volumes quoted elsewhere for Coke.
To get a handle on all of this, I fully fermented a small batch of Pink Lady juice from 1.050 down to 1.000 using S04 and a pinch of DAP.
Sugar syrup was added to the fully fermented juice to bring the SG up from 1.000 to 1.010 (20g/L sugar) and the cider was bottled filling 95% of each bottle so that the air space to cider ratio was the same in each bottle. The bottles were a 500ml plastic squeeze bottle, a 500 ml glass test bottle with a pressure gauge, and several 330ml glass crown seal bottles (no sense in wasting the leftover cider). They were all kept in the cool store at 18C.
Sorry if it sounds like a high school science experiment, but really it was just making another batch of cider and recording some numbers.
Trying to quantitatively assess the hardness of the squeeze bottle wasn’t very useful. The freshly filled 70mm diameter plastic bottle squeezed about 3mm (about 4%) at the start (i.e. gauge pressure of 0 bar). As the fermentation for carbonation progressed, at gauge pressure 1.6 bar (22psi) the bottle was hard and only squeezed by1mm. So, trying to relate gauge pressure to mm of squeeze was not practical.
I found that once the gauge pressure built up to more than 1.6 bar, the “squeeze bottle had reached its maximum hardness and didn’t change with more carbonation. So, that is about as far as the squeeze bottle goes for indicating carbonation pressure.
Gauge pressure of 1.6 bar is 2.3 volumes of C02 at 18C. i.e. a pleasantly carbonated beverage. This is only 10% below the common target of 2.5 volumes carbonation for cider.
It would be reasonable to take the time it took to develop 1.6 bar of pressure and extrapolate that to determine the extra time needed to reach a higher pressure.
For those who want to follow the numbers… I let fermentation continue until gauge pressure was 1.8 bar (2.5 volumes of CO2) and did a taste test with the squeeze bottle (Yum…a nicely carbonated cider with a touch of sweetness due to the residual unfermented sugar). At this point the SG was 1.007 so about 6.5 g/L of sugar had been fermented into 1.6 volumes of CO2. So, the numbers lined up O.K. since 1.6 volumes from the fermented sugar plus typically 0.9 volumes already in solution from the original fermentation equals 2.5 volumes, and so there was about 13 grams or 2½. teaspoons (½ teaspoon per glass) of unfermented sugar left). This seemed like a good time to hot waterbath pasteurise the crown sealed bottles.
So as a reward for all this work I am now drinking the squeeze bottle as I write, and will probably drink the pressure gauge test bottle tomorrow…win-win!
Cheers! I hope this helps someone.
