To test sugar and alcohol levels in Kombucha use a hydrometer, The hydrometer will show the concentration of sugar in solution, however it can also indicate the concentration of alcohol. A first reading at the start of fermentation and a second reading at the end of fermentation then divide the difference by 7.36. That's the alcohol produced, For example a Start reading of 1085 and an end reading of 1005 will give a difference of 80 and dividing this by 7.36 will give an alcohol content of 10.9% by volume. A little tricky for our ferments (Kombucha Mushroom Tea, Ginger Beer, Japanes Water Crystals) which range from 1/2 of 1% to 2-3-4 % if we really try to produce alcohol. For those of us who really don't want any alcohol the lowest possible reading is a good thing. We also have included soome information on determing sugar levels which is of interest to many of us, even though we are not diabetic (as yet) . AND also the hydrometer may test one's own urine, which may indicate dehydration or improper water metabolism. The hydrometer was not made for these purposes and therefore should not be concluded as a accurate test but as a relative means to judge where your kombucha ferment (or yourself) are.
Kombucha Modified Technique for Diabetics to test their kombucha sugar content the alcohol must be removed first by boiling,
Measure off 200 ml
Boil it until there is 100 ml left.
Add water to revert to the original volume.
Cool to room temperature,
Read the hydrometer
Multiply by 2 (the reading)
For example, if the hydrometer reads 1003 degrees, then the residual sugar will be 6 grams of sugar per liter, (1003 - 1000 x 2).
sugar converts almost one for one into alcohol, so a 5% sugar solution will yield roughly a 5% alcohol. The alcohol converts almost one to one into acetic and gluconic and other acids (leaving about 1/2 of 1 % residual alcohol. The highest alcohol reading for kombucha is really low compared to beer and wine. That is usually within the first 3 days. Thereafter it steadily drops typically ends with 1/2 of 1 %. A longer than typical ferment may result in all the sucrose (sugar) except for a small percentage of fructose and unfermentable sugars such as pentose. Typical expectations would be about 3-4 grams per liter. Every batch would be different.
The hydrometer may also read one's urine and be a early indicator of a disorder. This of course, is not FDA approved
Specific Gravity Urine: The specific gravity test permits the determination of urine specific gravity between 1.000 and 1.030. In general, it correlates within 0.005 with values obtained with the refractive index method. For increased accuracy, 0.005 maybe added to readings from urine with pH equal to or greater than 6.5. Elevated specific gravity readings may be obtained in the presence of moderate quantities (1‑7.5 g/L) of protein. The specific gravity of urine is a measurement of the density of urine; the relative proportions of dissolved solids in relationship to the total volume of the specimen. It reflects how concentrated or diluted a sample may be. Water has a specific gravity of 1.000. Urine will always have a value greater than 1.000 depending upon the amount of dissolved substances (salts, minerals, etc.) that may be present. Very dilute urine has a low specific gravity value and very concentrated urine has a high value. Specific gravity measures the ability of the kidneys to concentrate or dilute urine depending on fluctuating conditions. Normal range 1.005 - 1.030, average range 1.010 - 1.025. Low specific gravity is associated with conditions like diabetes insipidus, excessive water intake, diuretic use or chronic renal failure.
Accuvin Residual Sugar Test Kit are more accurate and made to test for fructose and glucose sugars. (but not the unfermentable sugars such as pentose).