Pectin test with alcohol

[Claude Jolicoeur]

After discussing this test in another thread, I thought it could be useful to explain a bit more, as this is a very easy test to make, and it can be extremely useful for all who (in particular) are attempting to make a keeved cider.

What's needed: a test tube and some very strong alcohol.
I use isopropyl alcohol 99%, bought in a local drugstore. Other types may be used, but it needs to be strong concentration.
According to this paper (http://www.ifpc.eu/fileadmin/users/ifpc/infos_techniques/Art_clarification_haute_RPAC_37.pdf), the mixture of alcohol and juice should be of the order of 75 to 80% for the test to give good results.
Hence I use 4 mL of the juice to test with 16 mL of alcohol, and this gives me a mixture at 79%. With a weaker alcohol one would need to use more alcohol and less juice to get to the target. (for example if alcohol was 90%, using 17 mL alcohol with 3 mL juice would give a mixture at 76.5%).

First use of this test is to evaluate if the juice contains enough pectin to form a good chapeau brun when keeving.
For my part, my late harvest apples are quite loaded with pectin and the juice keeves very easily.
I was pressing last week, and did the test. Here are 3 pictures.
The left most is taken 1 minute after mixture. We can see the pectin has started to form a mass in the bottom of the tube.
The second is taken 10 minutes later. Interestingly, the mass of pectin starts to rise, a bit like a chapeau brun...
And the third is an hour later, all the pectin mass is now on the top.
The test shows this sample of juice is quite loaded with pectin, and I am confident it will keeve without fuss...

A second use for the test is to check if there remains pectin after an enzyme treatment.

I have a batch where I started the keeving process 10 days ago. I now have a nice chapeau brun, but I want to know if the juice under the chapeau is completely depectinised. So I get a sample of the juice under the chapeau with a turkey baster and make the test. See picture taken 1 hour after. I can only see a couple of very small pectin gluts on the top, indicating that almost all the pectin has now been degraded. With a chapeau well formed and compacted, I will be able to rack this cider within the next few days.

Hoping this may be helpful to some...

Claude

[luis.ga...@gmail.com]

Can this test also be used in a juice or a fermented or a partially fermented cider that has been depectinised with a pectic enzyme to check if there is still pectin in?

Louis

[Claude Jolicoeur]

Sure.
If well depectinised, no pectin mass should appear (as in the last picture of my first post)
Claude

[Bartek Knapek]

Is it possible to tell from this test what level of pectin is "enough" to consider the juice for keeving?

I tested Boskoop and Idared (see attached), and the results indeed show significant differences.

So I tried keeving Boskoop, but there is no trace of chapeu brun forming (7 days @ ~9C), instead the juice is almost cleared, with all the sediment at the bottom.

I do by the book: 1/4 SO2, add PME, CaCl2 - I wonder if the problem is the juice, or...

/Bartek

[Claude Jolicoeur]

Le mercredi 30 novembre 2016 08:05:29 UTC-5, Bartek Knapek a écrit :

Is it possible to tell from this test what level of pectin is "enough" to consider the juice for keeving?

I tested Boskoop and Idared (see attached), and the results indeed show significant differences.

So I tried keeving Boskoop, but there is no trace of chapeu brun forming (7 days @ ~9C), instead the juice is almost cleared, with all the sediment at the bottom.

I do by the book: 1/4 SO2, add PME, CaCl2 - I wonder if the problem is the juice, or...

Impressive to see how much difference between these 2 varieties.
To me the Boskoop test would seem to show enough pectin. I think you should be more patient, 7 days is still too soon. You should see in another week.
One thing you could do is to retest the cleared juice to see if all its pectin has been transformed.
Claude