Grape sampling for white/rosé vs red?

[hptasins]

agree - 'soaking up' makes a huge difference. (See my recent Syrah thread for another example)

It also makes a difference how you press the grape samples, eg mashing up by hand vs blending. The latter will likely give more meaningful results, though it's a bit harder to measure pH unless you have a centrifuge to spin out the solids. You can prepare a suitable sample by passing through successive filters (eg a tea strainer followed by filter paper) but it takes a while.

I'm now trying to figure out how to get "meaningful" results when sampling for whites and rosé vs. red wines. Mashing by hand then soaking up for 5 hours seems reasonable for reds, but obviously isn't going to give a good representation of what you'll get when making white or rosé. But mashing and taking a sample immediately seems like it might go too far the other direction. Any thoughts or experiences? And how much pH shift to allow for when cold stabilizing?

I'm wrestling with picking decision for a PN rosé, and there's rain in the forecast for Monday ...

 

[BarrelMonkey]

I'm now trying to figure out how to get "meaningful" results when sampling for whites and rosé vs. red wines. Mashing by hand then soaking up for 5 hours seems reasonable for reds, but obviously isn't going to give a good representation of what you'll get when making white or rosé. But mashing and taking a sample immediately seems like it might go too far the other direction. Any thoughts or experiences? And how much pH shift to allow for when cold stabilizing?

I'm wrestling with picking decision for a PN rosé, and there's rain in the forecast for Monday ...

Great point. I was thinking of reds - would definitely just sample the juice (crushed by hand, not blenderized) for whites and rose.

pH on cold stab is a tricky subject. If you're below pH 3.65 or so (which you probably are with whites or rose), both pH and TA will decreaase on cold stabilization. Above that value, pH will increase and TA decrease. The amount is hard to predict unless you know the relative abundance of tartaric and malic acid and potassium, and even then I think it's an educated guess at best.

 

[Rice_Guy]

I'm now trying to figure out how to get "meaningful" results when sampling for whites and rosé vs. red wines. Mashing by hand then soaking up for 5 hours seems reasonable for reds, but obviously isn't going to give a good representation of what you'll get when making white or rosé. But mashing and taking a sample immediately seems like it might go too far the other direction. Any thoughts or experiences?

With gravity/ brix a fresh dirty juice seems accurate.
With pH/ TA the digital read out seems to take longer to stop drifting if there are obvious particulates.
With YAN testing obvious particulates (solids) seem to give a higher nitrogen reading

 

[hptasins]

Great point. I was thinking of reds - would definitely just sample the juice (crushed by hand, not blenderized) for whites and rose.

pH on cold stab is a tricky subject. If you're below pH 3.65 or so (which you probably are with whites or rose), both pH and TA will decreaase on cold stabilization. Above that value, pH will increase and TA decrease. The amount is hard to predict unless you know the relative abundance of tartaric and malic acid and potassium, and even then I think it's an educated guess at best.

pH for just-squeezed juice is well below 3. Brix is around 22. If I let the grapes macerate for a few hours, the pH shifts up a bit (Brix stays fairly constant).

The vines (not mine) are in pretty rough shape, some have completely shut down and some others are looking pretty close - few leaves, and any left have at least some yellowing. There are already many clusters with lots of raisins. We had temps >> 90F the last 3 days which didn't help. Cooler today and tomorrow, with some rain on Monday.

At this point, I'm thinking I should pick tomorrow, do some manual crushing (I don't have a stemmer/crusher), and macerate for a couple hours. Then press and see where it ends up. Between the maceration and doing cold stabilization later, hopefully the pH will move just enough to not require any deacidification. I'm not planning on doing ML, but that's an option too if the TA is way too high.

There are enough grapes that I'll do a second pick later next week for a red PN.

 

[hptasins]

Picked 137lbs this morning. Avoided the raisins or semi dried out clusters. Macerated 2/3 for a few hours, rest went into the press whole cluster. Pressed everything off this afternoon and ended up with 8 gal. Brix 22.6, pH 2.96. I'll rack tomorrow and take samples to a lab for full numbers.