Can you monitor gravity to monitor progress of a Kombucha fermentation

[Calder]

I've made a lot of beer and use Initial and Final gravity to measure amount of attenuation, residual sugars, and alcohol. In essence, determine if and when it is complete (and other information about the beer.

Is there any way to similarly monitor a Kombucha fermentation to determine if most sugars have been used up. I understand any measurement of alcohol would be pointless due to the conversion of alcohol to acid. Does anyone use an Hydrometer, or preferably a refractometer to monitor gravity to tell when the brew is mostly done?

 

[hottpeper13]

I am also curious about this so I started tracking hydrometer readings and pH on my last batch. At day 10 of fermentation I got 1.024(didn't think about the pH yet) and it was tart but could go longer. On day 13 it was 1.022 and very tart but good ,the pH was 2.85. This was the first time so many more measurements needed. Next time I will check gravity in cooled tea prior to pitching.

 

[Calder]

I started tracking hydrometer readings and pH on my last batch. At day 10 of fermentation I got 1.024(didn't think about the pH yet) and it was tart but could go longer. On day 13 it was 1.022 and very tart but good ,the pH was 2.85.

This is very interesting.

What was your initial volume, how much sugar did you use, and what type of sugar was it. You can easily calculate what the OG probably was.

I seem to remember from when I started brewing Berliner Weiss's, that the acid (lactic acid in that case) had a similar gravity to sugar, so you could not determine the amount of sugar remaining if you soured before adding yeast (which is the way I used to make it).

An hydrometer may be a useless tool in the normal Kombucha ferment. If you ferment anaerobically after souring to get some alcohol, it should help.

Keep taking measurements and report back. I'm bottling some tomorrow, I think I will take an hydrometer and a refractometer reading to see what it is.

 

[hottpeper13]

Those measurements were just before bottling. I add 1/2 tps of Costco organic pure cane juice sugar and a pinch of dry ginger for priming the bottle and wanted to know if that sugar is being eaten. Not sure if there is a correlation between gravity and pH but as with beer you want consistency. Once I have all the numbers and there close from batch to batch I might send to a lab for sugar and alcohol panels. I weigh the sugar , but the water goes to the rivets and not sure if it's close to 2 gal or not will check. I know what you are saying about the GU's and all, I use a calculator and brewing formulas for all my brewing.

 

[MarkKF]

so how low does it go? My wifes last batch started at 1.054 and it's at 1.024 now. Will it go completely dry before it becomes vinegar?

 

[Yooper]

so how low does it go? My wifes last batch started at 1.054 and it's at 1.024 now. Will it go completely dry before it becomes vinegar?

No, not necessarily. It should go lower, but not totally dry as acetobacter "eats" alcohol and releases vinegar, so it could get very vinegary far before getting dry. It's not all saccharomyces in a SCOBY (there are several strains of lactobacillus and a smaller amount of acetic acid bacteria) and it's not anaerobic- so it's not the same as beer and wine fermentations.