Know Your Honey: Acid and lactone

I’ve begun reading Composition Of American Honey by Jonathan White, which was published in 1962 by the US Department of Agriculture as Technical Bulletin 1261. It’s the most comprehensive survey of honey ever conducted, or likely to be conducted anytime soon, in the US. Reading it made me want to post about honey in my “Know Your Ingredients” series, which spotlights a different winemaking ingredient in each article. A single post will only scratch the surface of bulletin 1261, so today I’m starting an offshoot of that series called “Know your honey.” No, it isn’t a reality show where you find out the shocking truth about your Significant Other, instead I’ll be writing about different aspects of honey and how they relate to making mead. Don’t be too disappointed – not only will our mead be better for it, but our wives, girlfriends, husbands, and so forth wont be nearly as mad at us.

A better approach to a familiar problem

I’ve been trying to get a handle on the acidity in honey and mead. The problem, as I explain here, is that the normal tests, like titration, overstate acidity in mead because they include both the total amount of acid and the total amount of lactone. The last time I posted on the subject, I explained that those results can still be useful as an upper limit and outlined a procedure for managing the acidity in mead. What I really wanted to do was pin down the acidity accurately, and I had two ideas about how to do that. I’m going to use information from USDA 1261 to follow up on one of them today, and that is to use typical amounts of lactone in honey to correct measured titratable acidity values.

Dr White’s very useful data

Dr White determined the pH, amount of acid, which he called “free acidity”, the amount of gluconolactone, “lactone”, and titratable acidity, “total acid”, for 490 samples of honey.

Characteristic Average Standard Deviation Range
pH 3.91 not reported 3.42-6.10
Free Acid (meg/Kg) 22.03 8.22 6.75-47.19
Lactone (meg/Kg) 7.11 3.52 0.00-18.76
Total Acid (meq/Kg) 29.12 10.33 8.68-59.49
Lactone/Free Acid 0.335 0.135 0.000-.0950

Using the Lactone/Free Acid ratio to correct TA values

You might be wondering what the heck “meq/Kg” means. Well, rather than assume all the acid in any sample is tartaric, like most winemakers do, chemists express acidity as milliequivalents/Kg. This is a consistent, formal way of doing it that we’re not going to worry about because we’re not chemists and this article is getting technical enough. Besides, the really interesting part of the table is the ratio of lactone/free acid. This is exactly the information I was looking for and we can use it in two ways:

The average value of lactone/free acid is 0.335, and since total acid = lactone + free acid, free acid = total acid / 1.335. Now we can titrate a sample of mead, get a TA value that we know is overstated, and divide by 1.335 to get a corrected value.

Since the lactone/free Acid ratio varies, our correction will not be exact. We can use the average value and the standard deviation to get a range. The standard deviation is 0.135, which means, if these values are normally distributed, that almost 70% of the samples will have a lactone/free acid ratio between 0.200 and 0.470. From that we can corral the free acid in a range of total acid/1.200 and total acid/1.470.

An example

Let’s say you titrate a sample of mead and get a value of 7.5 g/L. You can use the simple correction of dividing by 1.335 to get 5.6 g/L or you can get a one standard deviation range by dividing by 1.200 and 1.470. That would give you a range of 5.1 – 6.3 g/L. I used 7.5 g/L in my example to tie it in with my earlier procedure of aiming for the high end of your target range. I illustrated this by looking at adjusting a mead’s acidity to match that of white wine. Since white wine can range from 5.0 – 7.5 g/L, I suggested aiming for 7.5, knowing that it would be less. Now we have a better idea of how well that would work because the one standard deviation range (5.1 – 6.3 g/L) puts it within the range of white wine.

Free acid has a huge impact on taste, and now that we know how to measure it, or at least estimate it well, we are well on our way to making better meads more consistently. I intend to continue this series on honey. To make sure you don’t miss these and other postings, subscribe to this blog. It’s easy, it’s free, and you’ll see every post without having to constantly check back.



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2 thoughts on “Know Your Honey: Acid and lactone

  1. Mitchell Omichinski

    Mr Erroll

    I have enjoyed all your bog on mead making todate. I have been trying for some time to obtain a copy of Composition Of American Honey Department of Agriculture Technical Bulletin 1261 by Jonathan White. Can you suggest a means to obtain this publication. Thanks

    Mitchell Omichiski

  2. Erroll Post author

    Hello Mr. Omichinski,

    As soon as I saw your comment, I realized that I should have included a link in my original post. Please excuse the omission. You can find a copy of bulletin 1261 here. Many of Dr White’s other papers are available here.

    Erroll

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