Tracking malic acid

Cellar Rats (ITB)
1

I have been wanting to buy an analytical instrument to track malic acid. I am looking into the OenoFoss, as it also does glu/fru, ph, TA, VA, alc., and color. This machine is $40k. This is more than I can afford at this point . Is there any other tool, other than paper chromatography that can roughly track malic acid? I always send out final samples prior to bottling, so it doesn’t have to be lab accurate. Any suggestions?

2

Get a spectrophotometer if you can afford one. Even if you did get an Oenofoss, malic is the weak point with that machine- you could track the malic going down, but you would still have to verify dryness enzymatically. I do malics, glucose/fructose/ nitrogens, and acetic acid with the enzyme kits on the spec.

3

Though it would work, I’m uncertain if this is within the realm you seek:

http://www.mondofacto.com/facts/dictionary?malic+acid+dehydrogenase" onclick="window.open(this.href);return false;

I do malics, glucose/fructose/ nitrogens, and acetic acid with the enzyme kits on the spec.

I guess I wasn’t that far off after all.

4

How much are these bad boys?

5

I highly recommend a spec, John. You can get a great one for $2,500, and I understand that there are some bare-bones versions for under $1,000 now. At $20/pop for a malic at a wine lab, that could pay for itself in a harvest. With a spec you can do other enzymatic analysis as well. RS works great. Acetics are possible. SO2 as well, though I understand it’s a little complicated. And you can do all your NOPA (nitrogen) analysis as well, unless, say, you happen to be busy at harvest.

After you fall in love with your spec you can do things like the Harbertson-Adams assay for tannin, monomeric phenolics, anthocyanins, etc. And of course you can do all the old fashioned color/tint/hue nonsense.

Kits for enzymatic analysis are relatively cheap, and it’s worth trying a few until you find the brand(s) you like, which may vary depending on the particular analysis. Check out r-Biopharm, Randox, and Megazyme, among others. And if you find yourself running a lot of analyses, you can get your costs down to pennies per by making your own reagents.

Seriously, cannot recommend it enough.

6

Any brand/s you can recommend?

7

At Seavey I used a Genesys 20 UV-Vis, I believe (the picture on the website does not quite match my memory), which I think runs around $2,500, though of course you should ask. You do want to make sure you can measure in the UV part of the spectrum for many of the analyses you’ll be using.

Also, in my experience specs hold up pretty well. You may need to change a lamp after a few years. If you can find one secondhand, you should feel pretty confident that it will work okay (due dilligence required, of course).

A friend of mine bought one of the sub-$1,000 specs for his small winery. Last I heard he was quite happy with it. I’ll try to find out the brand this weekend and report back.

8

Oops. Just found the Genesys 20 for sale here for under $1,800.
http://www.moyerinstruments.com/cart/uv-vis-spectrophotometers/genesys-20-spectrophotometer.html" onclick="window.open(this.href);return false;

9

SO’s on a spec? I’ve never ever heard of that.

10

Thanks so much, Matt. You’re the man!

11

Linda,

R-biopharm sells a kit for total SO2. I looked into it a few years ago and it seemed pretty complicated, so I decided to stick with Rippers. But if you are curious, here’s a link:
http://www.r-biopharm.com/product_site.php?language=english&product_id=480&" onclick="window.open(this.href);return false;

John, you’re welcome. Enjoy.

12

Thanks for the info, Matt. I doubt if I’ll be doing that any time soon.
[shock.gif]

13

What is the typical per assay cost of the malic and other kits offered for use on a UV spec? If doing less than 20 tests a year, is it worth it over doing less accurate (chromatography) and cheaper based tests to track, then a single ETS/Vinquiry test to finalize?

14

My tests are $2.01 per test from Megazyme, but that it just for the test itself- that does not include the cost of cuvettes, pipette tips, etc, not to mention the spec and the pipettors, etc.

15

I agree with Matt that you gotta get a spec . . .very handy piece of equipment . . .

You will also need to invest in a set of pipettes, pipette tips, and cuvettes . . .

I used to run RS, malics, and do the Harbertson Adams Assay on it . . . now I really only run malics . . .

You can also use it to run acetics (something many labs run in lieu of using a cash still to do VA’s) though I personally like running VA’s because this encompasses other volatiles in addition to acetic acid. You can run SO2s on it, but I would invest in an AO set up if you don’t already have one . . .

Another useful piece of machinery would be an auto titrator with a carrousel to hold multiple samples - will cost you about $10K plus but it is invaluable for running A LOT of phs, TAs and ripper SO2s. . . .

Cheers!

16

Hi, An alternate for some tests would be the Accuvin test strips. They don’t require any equipment purchase, and are almost as sensitive as the spectrophotometer method. The malic test takes only 4 minutes, and has a sensitivity of 30 mg/L. The L-Lactic (for confirming the start of MLF) takes only 2 minutes, and has a sensitivity of 10 mg/L. The Residual Sugar test covers the range of 100 - 2000 mg/L, below where a hydrometer of the Clinitabs are useful. A spect is a good tool, if you have the cash and the skill to maintain it and do the appropriate test calibrations. Lots of people think because the digital result has many decimals that it is reliable. Not always so, as an ongoing quality survey of winery labs points out (Collaborative Testing Services, Inc., Sterling Virginia, 2004, http://www.collaborativetesting.com/wine/current_reports.html" onclick="window.open(this.href);return false;:slight_smile: Food for thought.

17

I’ve used the Accuvin ML tests in the past and they have given me some false positives (falsely reporting the presence of ML when there was none, based on results from Vinquiry). So I’d proceed with caution here.

18

I hate threads like these - I have little clue what the hell you are talking about. I can, however, drive to ETS blindfolded.

19

It would be nice if testing facilities like Vinquiry would include the positive control results along with their reports (assuming they run them). It would have helped in this situation to know if Accuvin or Vinquiry was correct.

I think this year I’ll be buying a kit for malics from Randox for use on a spec. Seems like the most accurate and economical way to go. Plus, since I get to run the test myself, I can control the assay.