Vinegar and chemistry (cooking, fermentation)

[elainegrey]

Welp, just litmus strips and a refractometer are far from sufficient to understand vinegar's acidity content or wine's alcohol level. Need the hydrometer AND a titration system as well.

Cheese cloth is slightly superior to coffee filters in filtering because you can can squeeze out the juice from the stronger cheese cloth. So that seems like a useful investment that i will use again with jelly and sauces as well as this vinegar trip,

I bought glass straws to pull samples up, sort of like a "wine thief". "I'm getting a refractometer instead of a hydrometer," (which needs a moderately large volume to test bouyancy in), so i just need something to get little samples for the litmus and the refractometer. "I'll get a glass straw and i can put my finger over the end to control the sample." That does work. I was horrified, though, at the "buy glass straws to reduce plastic" sales pitch for the straws and the many many layers of plastic it was delivered in.

So the vinegar i am making is now significantly more expensive, and i still can't tell if it's acidic enough to be used for preserves. It turns out the acidity of some complex fluid like vinegar is not easily determined from the pH. That, and getting 0-14 pH strips leaves me squinting at the subtle color differences between a pH of 3 and 4 and 5. There are, i now see, pH strips for measuring just acids: maybe i'll invest in that someday. First, gotta use the vinegar i've made.

Comments

[cmcmck]

Cooking so often ends up as science!

[elainegrey]

Fermentations doubly so!

[amaebi]

Could you say more about the acidity of complex fluids?

[elainegrey]

Apparently a nice vinegar has other chemicals in it, which can change the pH profile -- the number of loose H atoms? Apparently the accurate way to measure the amount of acid is to add an indicator chemical, and the slowly add a base (titrating) until all the acid has been balanced by the base and the indicator changes color. I learned from the not too technical article below.

Smith, Reginald. “PH and Acidity – Their Difference and Importance in Vinegar.” Supreme Vinegar (blog), November 23, 2017. https://supremevinegar.com/2017/11/23/ph-acidity-difference-importance-vinegar/.

[amaebi]

Thanks!

As well as the intrinsic interest, I get the pleasure of realizing that had been framing acidity and pH as integrally identical, rather than recognizing pH as a measure associated with but distinct from acidity. I am a fool for epiphany. :D

[elainegrey]

I feel like this is something like the spherical cow story in physics. In teaching science and solving labs, we simplify so much, that perhaps the problem solving ideal is a little too far from reality: assume friction is negligible! Assume the angle of the pendulum is small! Assume there are no impurities in the water! Assume a spherical cow! https://en.wikipedia.org/wiki/Spherical_cow

[amaebi]

:D

[annie_r]

This is fascinating.
I have a hydrometer, but maybe not for the same level of specificity - I've only used it for terra sigillata.
This vinegar might be more expensive, but subsequent ones will not be once you have all the equipment?

[elainegrey]

I hope i am inspired to make more vinegar in the future (in which case, yes, less expensive). I used some in a marinade for mushrooms that turned out OK - -except i far over-roasted the mushroom. They're a little like slightly burnt bacon? (This from someone who hasn't had bacon in decades.)

[annie_r]

Mushrooms and almost-burnt bits are high-umami, so the similarity is understandable.
acidity/pH is head-exploding.