I am thinking of adding baking soda to sugarcane juice to eliminate the fruity acid that is present. The pH of sugarcane juice ranges from 4.5-5.5. I wonder how much baking soda should I incorporate every 1 liter of sugarcane juice. Thank you so much. This would really help me in my thesis.
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1$\begingroup$ Is experimentation at smaller scales possible? That would be the best answer, probably. $\endgroup$– Eashaan GodboleCommented Jul 17, 2019 at 14:17
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1 Answer
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You need to know which acids are present in the sample, or determine the required amount experimentally.
Without any knowledge of the pKa values of the acid or acids present, there could be very different scenarios. A pH of about 5 could be due to a high concentration of a weaker acid or a low concentration of a stronger acid. For example, 0.01 mM of HCl would bring the pH to 5, or 1 M of a weak acid with pKa of 10. Or it could be a buffer composed of an acid and its conjugate base present at similar concentrations, with the acid having a pKa of around 5.
This paper states that the main acidic component is aconitic acid (derived from citric acid), at 3 g per 6 liter (i.e. a concentration of about 3 mM). The pKa value for the first ionization is 2.8, and for the second 4.46. So if all of these assumptions are correct, the extract is buffered with a buffer that has a pKa of 4.46 and a concentration of 3 mM.
If possible, the best thing would be to add a buffer at higher concentration (say, 10 mM) with a pKa in the range of the desired pH. Alternatively, you could add any solution (or solid) that increases the pH, and determine through an experiment how much you need.
It is possible that the composition of the extract will vary from sample to sample as you are starting with biological material that shows some variation in its composition.
