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I have read about volatile compounds that are released and the acidity in the chocolate drops as it is refined. I tried to test the changes in pH. After 12 hours there was hardly any change in pH (7.1 to 6.9). It clearly tastes different even after 12 hours but the pH didn’t change. How can I measure and track and pH?
I’m not surprised that you didn’t see a pH change. pH (potential of Hydrogen) is a mathematical way to represent concentration of the Hydrogen ions in water. But chocolate is a fat system, not water, so your probe (I’m assuming you used a probe, not paper) isn’t going to have anything to work with. Your meter had no reading (neither acidic nor basic) and the interpretation of that is neutrality, i.e. pH 7. Your reading could have as easily gone from 6.9 to 7.1. It is basically just noise in the instrument.
When I was in the lab there was a procedure for measuring the acidity of solids and oils that had known high levels of acids in them. We mixed the oil in a 1:10 ratio and mixed it for one hour at room temperature, removed the oil layer and measured the pH of the resulting water. The results we produced had a pretty high variation but was good enough for knowing if the oil was considered highly acidic (pH < 2) moderately acidic (2<pH<5) or neutral (pH>5) but was pretty much useless for telling if one neutral oil was more or less acidic than another neutral oil. They method had too much variation.
I was able to get a moderately acceptable result with pure cocoa butter but I had to stray from the published method because cocoa butter isn’t a solid at room temperature and heating the mixture (so the cocoa butter was melted) to a constant temperature for one hour was difficult. It had to be kept at a constant temperature because the heat changed the extraction rate and amount of the acids in the butter.
The chocolate I attempted failed. Over. And over. And over. The solids of the chocolate got in the way. At the proscribed 1:10 dilution the chocolate not unexpectedly seized after an hour. I tried 1:100 but the results showed a neutral solution due to the high dilution. It was rather a no win situation.
At the end of the day I can’t offer any good way for you to measure and track the acidity, at least with a method that will give you a number. I’ve heard about some methods for heating the mixture and measuring the amount of acids being driven off but that isn’t really going to give you an indication of what is in the chocolate and I doubt you can readily obtain the equipment. Regardless, I’m not sure any large scale manufacturers are testing the acidity to determine when a chocolate is finished.
The best I can offer is your own observation back at you. You noticed you could taste a difference. Do that. Taste your chocolate. Your sense of taste is a wonderful instrument and what counts. Not numbers in this case. They are helpful for roasting and fermenting but not acidity and telling when your chocolate is done.
This could be just a myth, but I’ll relate it anyway. I heard that Hershey has a chocolate evaluator who is the final word on determining when the chocolate is finished. The sophisticated method used to determine when the chocolate is finished is nothing more than his sense of taste and smell. Certainly Hershey would employ instrumentation if they could, but they don’t. They taste it.
I suggest you do the same.