Wierd off-taste w/Zin (not noticable to most)

Pete, It's hard to say, how do your airlocks look? When you buy them they usually have a little waste on them on the seams. I trim that off where it goes into the bung. I had a few wines go off for no reason I understood untill I began doing that, I get it smooth on all of them and have no issues now.

Joe

Hi.....for what its worth,my Zin last year had an off taste that I couldn't identify....almost sherry like.....I recently talked to my produce supplier about this years winegrape order and was informed that last years shipment of california grapes was very poor , also confirmed by a local fellow winemaker I recently met....perhaps sprayed with a preservative of some sort???.andy j.

Pete, Are you sure it isn't C02? Take a bottle and drink half. Then shake the bottle vigourously. If there is more than 1/2 inch of foam you could still have dissolved C02 in it. I "think" that might be your answer.

Bob

That's almost certainly due to too much oxygen exposure and insufficient free SO2.

Tom S

Andy, I don't know about that. I made California wines last year and they are good. Western Pennsylvania grapes were awful, that I agree with. They still made good wine, just took more effort (A lot more effort).

A sherry-like taste is usually a sign over-oxidation, either not enough sulfite or too much headspace ( more likely). The preservative they usually spray on grapes has sulfur in it and you don't spray them near harvest; the problem that usually causes is a stink, like rotten eggs (H2S).

Joe

Hi......glad your grapes were good last year......ours were not apparently.....this was a direct confession by the supplier/produce wholesaler who supplies our region....he had plenty of complaints 4 months after delivery I guess........my sherry like observation may have been inaccurate as the amount of sherry i've drank in my life might fill a thimble.......the grapes(zin) were high brix....26-27.....and I may have left too many stems in the must ....prolly 20%....I sulphited as would normally but have no accurate way of measuring ph.....I made 2 batches of "false wine" as well and results were the same....drinkable but disappointing...hoping for better luck with merlot in a few weeks.......ALSO.......how accurate are litmus strips?.....andy j.

Nowhere near good enough for winemaking. Even narrow range pH paper is useless. You need a pH meter with resolution to 0.01 pH units.

Tom S

There are winemakers who would strongly disagree with that statement. Infact, there was a hotly debated thread on this ng on it some time ago (see thread "Using narrow range pH papers").

Ben

Ben, I'm not one of them, I would never use pH strips for winemaking, narrow range or not. A decent meter and a few years worth of buffers can be had for around $100 (US). Why take a chance? Getting accurate data is everything. Joe

Joe,

I know this is your position (from what you wrote in the very thread I mentioned). I think it is unfair to say they are "useless", however I completely share your point of view that accurate data is very important and a decent pH meter is well worth having (I personally would not use narrow range pH strips either).

I maintain my opinion expressed in that thread too: essentially that pH accuracy is important (e.g. in terms of SO2 additions). Like all things in winemaking, decent wine can be made without accuracy, but it's a much more hit and miss afair.

Ben

Hi Ben, I follow you. I am pretty interested in repeatability also and that goes more toward my comments than anything else. That said, I'm doing something related to this you may be interested in.

I've been doing another experiment and it would relate to narrow range pH strips also.

I have been testing samples before degassing and after. Degassing, even of wines that appear still, seems to be significant; Returning the sample back to it's original volume is also important. It seems pre-degassed samples can read high by at least 0.1 pH, and the TA reads high too. That's counterintuitive to me. I was just fooling around before and will start keeping some data now.

I guess I'm saying the process is as important as the equipment when measuring acidity.

Best regards, Joe

Joe,

Interesting observations. Are you saying this for when the sample has been diluted back to it's original volume or for when it has not (or both)?

Actually, I don't see why you'd really want to dilute the sample back. I mean, eventually that CO2 is going to come out of solution (in a non-sparkling wine) and the data you'd want is surely for what the final values (and final volume) are going to be (unless you take a very minimalist approach, it shouldn't be too long before the CO2 comes out either). Comments?

Very true.

Ben

Joe, Ben

What is the boiling point for Tartaric acid ?? TIA

Frederick

Hi Ben,

I used to not worry about returning the volume to original until I measured it, I'm losing about 3%. Now I correct for that and return it to the original volume.

As soon as I see bubbles I pull the sample out of the microwave and cool it back down to room temperature. That's when I return it to the original volume. I'm pretty much using Margalits procedure from Winery Technology and Operations; he suggests a 100 ml sample, but I use 50 ml.

I'll probably do some testing this week, I have 6 or 7 batches going now. I'll post the results.

Fred, I'm not sure I understand what you meant by the boiling point of tartaric, but I'm pretty sure the sample does not have to boil; I think it has to get to around 180 or 190 F. I figure it doesn't hurt to boil, you know you drove off the CO2 once it boils.

Joe

I haven't done extensive testing on this idea, but I think it would be easier to put your sample into a 187mL bottle and use one of those vacuum-wine-saver stoppers which would allow you to essentially pull enough vacuum on the sample to degass it without heating it up.

CHEERS!

Joe,

I'm not sure if you missed the point I made in my previous post: that I don't really see the point in adjusting the volume back to the original. The CO2 is eventually going to come out of solution anyway, so why not just take the values for when the CO2 will be out of solution anyway? Unless that CO2 is going to be in the wine for ages (atypical) then I see no reason why the values taken at the time when the CO2 is in are really relevant. You follow?

I await with interest.

Fred,

I'm not sure what you mean by the boiling point of tartaric acid either. Do you mean: how does the presence of a certain amount of tartaric acid in a wine solution affect the boiling point of that solution?

Ben

Nope. Just a straight forward question. At what temp does Tartaric acid change from a liquid to a gas. Just thought you or Joe would know the answer off the top of your head.

A comment, if I may, on the original topic. The original volume of the sample has to be restored when measuring pH because pH is a measure of

Frederick

Yeah, sure, I have memorised the boiling point of most organic acids ;-) Seriously though, I think tartaric decomposes (at around 210 C) - so it doesn't really have a boiling point.

That doesn't make sense to me. TA is a concentration (mass/volume), not a quantity (mass). If you change the volume, you change the concentration. When you boil wine, the mass of acid will stay constant whilst the volume will change, thus changing the TA.

Ben

True - BUT..... The test (itself) determines how much base it takes to neutralize an unknown quantity of acid. Since (as you say) the quantity of acid remains constant, then the test result will also remain constant. This info is then used to

Frederick