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Time v. Temp in reduction

post #1 of 11
Thread Starter 
I'm making some brown chicken stock & I plan to use some of it for glace de poulet. Is there anything to be gained flavor-wise by reducing it very slowly @ say 150 f as opposed to just boiling the **** out of it? I've had very good results using low-temp reductions of wine - fewer volatile goodies vape off at lower temps - & figure the same principle should apply to stock.

But reducing half a gallon of stock @ 150 f is going to take a long time, & it seems to me that such long exposure to heat, even if it's below the boiling points of various flavor compounds, will have to cause some degradation in & of itself.

Where's the sweet spot? (time isn't an issue - I can leave the stuff in a slow cooker with the lid off overnight if need be).

Also, I've always added the mirepoix etc at the last hour or so of cooking. It occurred to me today that I might get more oomph out of the deglazing liquid if I held it till the end as well. I'm going to try this in any case, but if anyone has any thoughts about this I'd love to hear them.
The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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post #2 of 11
Never thought about this before. I always reduce as quickly as possible. Just watch it.
post #3 of 11
Depends on the level of quality you're reaching for.

Stock is an infusion, just like tea or coffee. Would you choose to intensify the flavor of either by boiling?

On the other hand, you're right that 150F is too slow. It's not hot enough (except at extreme altitude). Assuming sea level, go for the hottest temperature below a boil you can maintain, probably 195ish.

The slow cooker at 150F is still a way of shortcutting the amount of attention you have to pay. There's a certain tradeoff in absolute time. Whether or not there's also a dimunition in quality, I can't say.

Mirepoix is ALWAYS added very early in the process in order to extract the maximum amount of the best flavor. If you want vegetables in your soup, strain the stock, and add the vegetables very late in the soup making process. Onion, carrots, and celery aren't always mirepoix; sometimes they're just veg.

If you add mirepoix as part of a deglaze, the mirepoix goes in before the deglazing liquid and is allowed to brown -- which makes it sweeter in its own right -- and helps create more fond. If mirepoix, as a rule (with exceptions) it's strained out before serving. If, on the other hand, it's a fine dice of aromatics intended for the table as in any sort of jardiniere, cut the vegetables attractively (e.g., "fine dice), saute them in a separate pan until browned and add to the nearly completed deglaze as late as possible; and if the deglaze depended on mirepoix, strain the mirepoix, and press the essence into the sauce before adding the fresh jardiniere.

BDL
post #4 of 11
Thread Starter 
Thanks, bdl -

The question stems from reducing wine. I've done 2 cups of wine + aromatics reduced to 1 cup both by boiling & slowly @ ~175f side by side & the low-temp reduced wine retained quite noticeably more complex flavor than the boiled wine. I wondered if the same principle might apply when reducing stock down to glace, & whether the much longer time spent at a still relatively high temp might cancel out those gains (if any) anyway.

As for adding the mirepoix & sachet for the last hour, those are the directions in the CIA textbook, & it made sense to me. Why boil vegetables for 6 hours? You don't when making vegetable stock.

I wound up boiling the stock to reduce it.

Hmmm - I kept a quart of the the stock aside... I could slow-reduce that & then I'd have a side-by-side comparison... will post results if I decide to go ahead & do that.
The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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post #5 of 11
I think when you boil a stock it re emulsifies the fat into the stock which is why it is usually kept at a slow simmer -- so you can skim the fat off. I assume with the fat re emulsified it would just change the mouth-feel of the stock.
post #6 of 11
Thread Starter 
That is my understanding as well. I strained & defatted the stock before I reduced it.
The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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post #7 of 11
Maybe I'm not sure exactly where in the process you are; but mirepoix which is going to be strained out and pressed, should be added as soon in the process as possible in order to ensure complete extraction and intensification. In some cases, it should be strained out after only a few hours in the pot, but that's a different story. The essence is still added and made a part of the reduction asap.

I'm probably more conservative and old-fashioned when it comes to technique than whomever wrote that particular section of the CIA textbook; and for whatever it's worth, my advice is better.

Oh well.

Looking forward to it.

Good luck,
BDL
post #8 of 11
Wow, that is a bold statement.

For whatever it's worth, when I make a brown stock i will caramelize the mirepoix after roasting the bones, wrap in rinsed cheesecloth and add to the stock for just the amount of time necessary to infuse the flavors, then remove and discard. White stock I add my mirepoix toward the end of the reduction to highlight the flavors, not mute them. I'm not a "pusher" when it comes to passing the solids through a chinois, makes the stock cloudy.
Baruch ben Rueven / Chanaבראד, ילד של ריימונד והאלאן
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Baruch ben Rueven / Chanaבראד, ילד של ריימונד והאלאן
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post #9 of 11
You're tea-bagging your mirepoix. Cool.

With white stock, I add the ingredients in the same sequence and with the same timing as I would for a normal (yellow) or roast chicken (brown) stock -- but don't use anything that would add color to the stock. For instance, the chicken is raw and the mirepoix contains parsnip rather than carrot in order to avoid coloration.

In my experience as a saucier, what's important about white stock is the color -- or rather lack of it -- and not any extra flavor. White stock is more about presentation and delicacy than flavor, and a good thing too. As a rule, the darker the stock the more flavor.

Furthermore, I think that less time in the stock for the mirepoix means less flavor. Less time doesn't "highlight," just the reverse.

I don't pass the solids through a chinois, I extract the moisture, and their last bit of essential juices by pressing them the back of a wooden spoon in a very fine sieve. If I thought I was getting solids, I'd add a layer of cheesecloth to prevent that. No way will I let those essences go to waste. They are structure, they are part of the spine of flavor, they make a difference.

If I'm attempting a completely clear stock, no matter how careful I am during the process to eliminate solids, I'll clarify the stock as a nearly final step by fltration with an egg-white raft and/or a cheesecloth lined sieve. Then, I'll sieve again just before service. just to break up any remaining air bubbles -- for clarity and silkiness.

However, that's another thing entirely. In this case, the OP is working towards a glace, not a buillon or consomme; and that sort of clarity is unnecessary.

BDL
post #10 of 11
vérité dans la cuisson
Baruch ben Rueven / Chanaבראד, ילד של ריימונד והאלאן
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Baruch ben Rueven / Chanaבראד, ילד של ריימונד והאלאן
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post #11 of 11
Thread Starter 
As to when to add the mirepoix, most recipes do put everything in at once, but adding the mirepoix for the final ~hour only is a fairly common move, not just limited to The Professional Chef (the CIA textbook).

I did just look at half a dozen vegetable stock recipes; only one called for simmering even an hour & a half - most were an hour or less.

I don't doubt your experience, BDL, but this doesn't make sense to me as a matter of logic. It's notoriously difficult, apparently, to get enough flavor into vegetable stock, yet no recipes call for simmering the veggies for 6+ hours. Why should vegetables behave differently in a meat stock?

(PS: when I said I reduced my stock by boiling, I didn't mean a full rolling boil. It was in fact right about 195-200f. Also, the quart of stock I had left over had to be used, so I can't do a super-slow reduction v. simmered reduction side-by-side with this batch. Maybe next time).
The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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The genesis of all the world's great cuisines can be summed up in a four word English phrase: Don't throw that away.
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