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Demi Glace - The Topic


hollis
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Is that who I am? The 'other poster?' Well, since quoting etiquette seems to have gone out the door, tell 'that guy' who said re-boiling stock 'works in the real world' that 'working' is subjective. Sure he survived boiled stock and maybe it didn't taste terribly off, but the bacteria were there- in very 'real' way.

Why take unecessary chances with food? Freeze it.

P.S. If you work in a kitchen, don't get caught by the health inspector doing that 're-boiling' bullshit.

Edited by scott123 (log)
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P.S. If you work in a kitchen, don't get caught by the health inspector doing that 're-boiling' bullshit.

Could you elaborate? How does ten minutes of simmering not kill bacteria?

I know it's traditional in French kitchens to keep stock pots going for days at a time, getting depleted and replenished (but not completely changed). And it's also pretty normal procedure for certain soups and stews (like a pot au feau) to be kept going almost perpetually through refrigerating, replenishing, and simmering.

I haven't seen any science related to this; if you know of any I'd love to check it out.

Notes from the underbelly

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P.S. If you work in a kitchen, don't get caught by the health inspector doing that 're-boiling' bullshit.

Could you elaborate? How does ten minutes of simmering not kill bacteria?

I know it's traditional in French kitchens to keep stock pots going for days at a time, getting depleted and replenished (but not completely changed). And it's also pretty normal procedure for certain soups and stews (like a pot au feau) to be kept going almost perpetually through refrigerating, replenishing, and simmering.

I haven't seen any science related to this; if you know of any I'd love to check it out.

From Bone Appetit by Robert L. Wolke

…according to my correspondents, among them a food safety consultant and a biochemist at the National Institutes of Health. It seems that all bacteria are not necessarily killed at 212 degrees Fahrenheit. Some of them can survive by forming highly invulnerable spores.

…A common pathogenic -- disease-causing -- genus of spore-forming bacteria found in soil, water and the intestinal tracts of humans and animals is Clostridium, especially the species C. perfringens, which is a major cause of food poisoning, and the much rarer C. botulinum, which produces botulin toxin, one of the most potent poisons known. Clostridium bacteria don't need oxygen to live; in fact they can't survive in air, so the interior of a pot of stock is a perfect growth medium.

To kill these spores, temperatures higher than 212 degrees are needed. That's why medical and surgical equipment is sterilized in an autoclave, a sort of pressure cooker.

Quoting guidelines prevent me from posting more of the article- I highly recommend reading the whole thing as it goes into far more detail regarding the ways in which these bacterial spores can survive boiling temps.

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Correct me if I'm wrong, gentlemen, but the presence of those spores in the stock is contingent on the bacteria being there in the first place. Which-- given that the bones are roasted at 400, the vegetables are caramelized at 350 or so, and the water is chlorinated, UV-treated, and boiled--shouldn't be the case.

This is why I love Classical cooking: If you do it right; if you perform each (in itself) very simple step right, you almost can't go wrong. Also, I would like to point out that commercial, feedlot beef and henhouse chickens are much more loaded with (for lack of a better term) impurities. I've been getting grass-fed bison and mixed-breed beef bones for my beef stock. It's cool, everything behaves exactly as Auggie E says it should; no need to correct or tweak at all. I buy free-range chickens from an Amish family 30 miles from here, and until the restaurant started getting in whole ducks, I sourced my duck bones from the sky. No overcrowding issues there I believe. I hope Wisconsin can get the Chronic Wasting Disease thing under control soon, because I miss my venison glace.

This whole love/hate thing would be a lot easier if it was just hate.

Bring me your finest food, stuffed with your second finest!

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Correct me if I'm wrong, gentlemen, but the presence of those spores in the stock is contingent on the bacteria being there in the first place.  Which-- given that the bones are roasted at 400, the vegetables are caramelized at 350 or so, and the water is chlorinated, UV-treated, and boiled--shouldn't be the case.

Reefpimp, the bacterial spore threat relates only to the myth that re-boiling stock every few days will maintain it's freshness/edibility. The initial process isn't in question. It's the post-cooled stock we're talking about. During cooling, micro-organisms from the air take root. This is where the threat stems from. Re-boiling it every few days does nothing to remove that threat.

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Is that who I am? The 'other poster?' Well, since quoting etiquette seems to have gone out the door, tell 'that guy' who said re-boiling stock 'works in the real world' that 'working' is subjective.  Sure he survived boiled stock and maybe it didn't taste terribly off, but the bacteria were there- in very 'real' way.

Scott, my apologies if you were offended; the reason I didn't quote you by name is that your quote was on a previous page when I was posting, and I couldn't figure out how to scroll back to see your name (and I don't know how to do the multiple quotes thing). No rudeness intended; you're reading a negative tone into my post that I assure you isn't there.

Regarding the quote from Bone Appetit (which I will read, thanks for the recommendation), every C. perfringens outbreak I've read about was related to improper cooling/holding, usually of big roasts, rather than prolonged storage of liquids at fridge temperatures followed by full re-heating. Here's the most similar case I could find, this from the US FDA's 'Bad Bug Book':

"In November, 1985, a large outbreak of C. perfringens gastroenteritis occurred among factory workers in Connecticut. Forty-four percent of the 1,362 employees were affected. Four main-course foods served at an employee banquet were associated with illness, but gravy was implicated by stratified analysis. The gravy had been prepared 12-24 hours before serving, had been improperly cooled, and was reheated shortly before serving. The longer the reheating period, the less likely the gravy was to cause illness." (italics mine)

This shows that properly reheating liquid does kill this bacteria, even in an extreme situation where the product wasn't cooled fast enough and the bacteria multiplied to dangerous levels - something that's not the case in my kitchen. Labensky's 'On Cooking' textbook also says C. p. can be prevented by re-heating to 74c or higher. So while I don't wish to dispute Wolke on C.p. possibly being able to survive boiling, from a practical as well as historical standpoint, re-boiling does seem to work.

Hong Kong Dave

O que nao mata engorda.

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Is that who I am? The 'other poster?' Well, since quoting etiquette seems to have gone out the door, tell 'that guy' who said re-boiling stock 'works in the real world' that 'working' is subjective.  Sure he survived boiled stock and maybe it didn't taste terribly off, but the bacteria were there- in very 'real' way.

Scott, my apologies if you were offended; the reason I didn't quote you by name is that your quote was on a previous page when I was posting, and I couldn't figure out how to scroll back to see your name (and I don't know how to do the multiple quotes thing). No rudeness intended; you're reading a negative tone into my post that I assure you isn't there.

Regarding the quote from Bone Appetit (which I will read, thanks for the recommendation), every C. perfringens outbreak I've read about was related to improper cooling/holding, usually of big roasts, rather than prolonged storage of liquids at fridge temperatures followed by full re-heating. Here's the most similar case I could find, this from the US FDA's 'Bad Bug Book':

"In November, 1985, a large outbreak of C. perfringens gastroenteritis occurred among factory workers in Connecticut. Forty-four percent of the 1,362 employees were affected. Four main-course foods served at an employee banquet were associated with illness, but gravy was implicated by stratified analysis. The gravy had been prepared 12-24 hours before serving, had been improperly cooled, and was reheated shortly before serving. The longer the reheating period, the less likely the gravy was to cause illness." (italics mine)

This shows that properly reheating liquid does kill this bacteria, even in an extreme situation where the product wasn't cooled fast enough and the bacteria multiplied to dangerous levels - something that's not the case in my kitchen. Labensky's 'On Cooking' textbook also says C. p. can be prevented by re-heating to 74c or higher. So while I don't wish to dispute Wolke on C.p. possibly being able to survive boiling, from a practical as well as historical standpoint, re-boiling does seem to work.

Dave, I did read a dismissive tone into your post, and I also flew off the handle (just a little bit :wink:), which I apologize for doing. I can now see that you weren't being dismissive at all.

I think it's important to convey the fact that I don't see the perpetuation of the re-boiling myth as a public health crisis. I don't think x number of people are dying every year because of consuming re-boiled stock. Or even x number people are getting sick. Re-boiling probably does kill off quite a few bacteria, and, although many people subscribe to the re-boiling paradigm, I get the feeling that very few people actually re-boil stock, and, those that do probably don't re-boil it more than a couple of times.

The chance of getting sick from re-boiled stock is probably extremely low. My guess is that it's far less than getting sick from a raw egg and that's 1 in 10,000 (if you live in the NE US and even less elsewhere). It could very well be in the realm of 1 in 100,000 or even 1 in a million.

My point is 'why take the chance?' Do you really want to be that millionth person? Would you want your loved ones to be? Your restaurant patrons? If you freeze the stock, the threat is removed.

For me, the autoclave example is especially compelling. If boiling kills all the nasties, why do hospitals use autoclaves?

If re-boiling was portrayed as a last resort, I think I'd be okay with it (I found some stock in the back of my fridge that's 10 days old, what do I do?). My problem is the perpetuation of the idea that stock can be re-boiled indefinitely. Months, years, decades. That concerns me- the portrayal of this repercussionless utopia where stocks live longer than we do :smile:

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Well, thanks for taking the time to at least think about what i said. And consider this in re the re=boiling: Botulism is anaerobic, and C. Perfringens is a micro-oxyphiliac (I think that's the right term). So by the very act of boiling, even very gently, it aerates the stock quite thoroughly, and thus providing a hostile environment.

No, stocks won't survive forever. But for safely storing glace for a few months, I think we're all gonna be okay if we follow HAACP guidelines and exercise a little common sense. Besides, it's healthy to expose your body to toxins every so often, right? Isn't that what Friday nights after close are for??

Edited by Reefpimp (log)

This whole love/hate thing would be a lot easier if it was just hate.

Bring me your finest food, stuffed with your second finest!

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Let me tell you guys what I think about storing demi-glace for home use. Don't bother, find a restaurant that makes their own, make friends with the chef, and barter, barter, barter. It's generally not worth buying what is sold as demi-glace, and making your own is worthless, because you throw away too much to spoilage. I make my own because I like cooking, some would call me crazy. I don't keep demi-glace however, reduce it by half and store it as glace de viande in small cubes in my fridge in glass jars, ten pounds of beef(chicken, pork, other game or fowl bones also acceptable) keeps me for six or eight months that way. I guess it's not right to call it glace de viande(a la Jacques) as it is not the result of a second boil but simply an extended first boil. Really, it is just demi glace reduced over medium heat for a while, then over low until there isn't any water. When it gets moldy, you didn't do it right, re melt, and further reduce, and throw it away if there is any other mold besides white mold on it. There is a noticable a taste difference to demi glace, but in no way is it bad, and it should not taste burnt (you also screwed up). It's good for some recipes, not for others, if any other way is better, school me egullet. Does anybody who lives by the ocean do this with fish, if so what kind?

Edited by coquus (log)
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I was just reading the Les Halles Cookbook while I was eating lunch and saw that AB said that a lot of chefs don't even bother with the veal demi-glace now--just do a dark chicken one--any thoughts on this?

I'm going to make a D-G in the next few weeks--have to collect the bones--which is more versatile in your opinion? Obviously the chicken one won't have quite as much of the gelatinousness of the veal base--any other differences?

Z

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I do both. I don't actually roast my veal bones - following on Thomas Keller's method, I find the non-roasted demi lends a more subtly sweet, round and versatile quality to many other sauces. My dark chicken "demi," made with roasted bones, meat trim, and vegetables, is just as gelatinous, just as useful, but has more of a roast quality, for obvious reasons. When I want a more pronounced or sharper character of this sort, I will go with the dark chicken.

-Paul

 

Remplis ton verre vuide; Vuide ton verre plein. Je ne puis suffrir dans ta main...un verre ni vuide ni plein. ~ Rabelais

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Wasn't it discussed in the thread on storing demi that much of the gelatin in stock is broken down in making demi?  I know not all, as the demi itself is quite thick, but I got the impression that demi is not a substantial source of gelatin.  Is this wrong?

I read the thread, but I'm afraid I can't agree. Gelatin is a breakdown product of collagen, but from what I know, gelatin itself is not heat labile; it survives heating quite nicely. If it didn't, glace would not be as thick as it is...

Looking through McGee on the subject:

Gelatin owes its remarkable properties to a peculiar amino acid makeup...which gives it a great affinity for water molecules, prevents its chains from coiling into more compact helical structures, and prevents the chains from coagulating when heated.  Some sauces, especially the concentrated, starchless reductions favored in the "nouvelle cuisine," owe their texture entirely to their gelatin content.

- i.e., classic espagnole based sauces would be aided by starch, and the imperfect proteins found in flour. But today's reduced stocks are almost entirely thickened by the gelatin present; even moreso, for true glace.

Edited by paul o' vendange (log)

-Paul

 

Remplis ton verre vuide; Vuide ton verre plein. Je ne puis suffrir dans ta main...un verre ni vuide ni plein. ~ Rabelais

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Wasn't it discussed in the thread on storing demi that much of the gelatin in stock is broken down in making demi?  I know not all, as the demi itself is quite thick, but I got the impression that demi is not a substantial source of gelatin.  Is this wrong?

I read the thread, but I'm afraid I can't agree. Gelatin is a breakdown product of collagen, but from what I know, gelatin itself is not heat labile; it survives heating quite nicely. If it didn't, glace would not be as thick as it is...

Looking through McGee on the subject:

Gelatin owes its remarkable properties to a peculiar amino acid makeup...which gives it a great affinity for water molecules, prevents its chains from coiling into more compact helical structures, and prevents the chains from coagulating when heated.  Some sauces, especially the concentrated, starchless reductions favored in the "nouvelle cuisine," owe their texture entirely to their gelatin content.

- i.e., classic espagnole based sauces would be aided by starch, and the imperfect proteins found in flour. But today's reduced stocks are almost entirely thickened by the gelatin present; even moreso, for true glace.

Gelatin slowly breaks down/loses it's ability to gel/thicken when heated. When exposed to the higher temps involved in reducing demi-glace and glace, this process is accelerated. Yes, demi is thick and glace is thicker and both do get their body from gelatin, but neither have the totality of body of the stocks from which they were made. A substantial loss of body/viscosity occurs.

Split a stock in half, make a demi with one part, then dilute that demi with enough water to match the volume of the other half. Chill. The water diluted demi will have a fraction of the gelling ability/mouthfeel of the unreduced stock.

The idea that prolonged heat damages gelatin's ability to gel/provide body is fairly well known. This is why you should simmer stocks until all the collagen is extracted but no further. If you keep simmering them indefinitely, the collagen will continue to break down and body will be lost.

From Dr. Bernard Cole, Food Scientist and Gelatin Specialist

It should always be remembered that heating, slowly destroys gelatin's gelling ability so one should always use the least amount of heating possible and for the shortest time possible.

From the Gelatine Manufacturers of Europe

Never add gelatine to boiling liquid because it loses its jelly strength.
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Scott, that would be an interesting experiment. I do wonder, though, if it would be hard to detect any differences between a dilute demi-glace and non-reduced stock - whether it would or wouldn't exceed a sensory threshold. It would be interesting to send it to a lab and compare molecular weights.

All I speak from is my experience. My demi-glace was made over the course of 3 days - strong stock, day 1, remouillage, and final reduction/clarification; a total of 14 hours or so of simmering. If the gelatin was that heat labile, I would expect that on day 3 - when bones are no longer present, and collagen extraction was no longer taking place - the stock would thin, rather than thicken; I am not extracting any collagen any longer, but merely reducing. Even though we are evaporating water, if the gelatin was broken down, all we should end up with is less, thin stock, not a viscous demi or glace. Additionally, since collagen is preferentially labile when compared to gelatin, its breakdown product, I also wouldn't think it would remain in favor of that breakdown product.

I did find some interesting info in this regard:

Gelatine Use in the Dairy Industry

Among other things, what they write squares with my understanding:

Gelatine, with its unique molecular structure has some very interesting properties which are virtually unaffected by "denaturants" like modification of the thermal or charge environments, because the protein is already denatured.

(denatured from collagen).

From what I have read, it is true that gelatin undergoes thermo-labile destruction at temps higher than boiling (actually, from what I've read, high temps induce reformation to helical, collagen-like structure - not dissolution to simpler forms), such as are obtained under pressure; but at normal boiling, no such destruction occurs. See

Stanford Study - Properties of Gelatin

-A very interesting study on the chemical properties of gelatin, from the point of view of many stressors and conditions. Among other things, I think a concluding comment is relevant:

Thirdly, gelatin features a rather wide temperature range of the glassy state with the upper limit of 205°C-210°C. This characterizes gelatin as a material with a fairly wide range of heat resistance.

In the range of normal simmering, in particular, gelatin is shown to exhibit reversible properties:

In the second region (20° to 120°C) the behaviour of gelatin is mainly determined by its moisture content. The thermal contraction of cold and hot gelatin films observed in this temperature region (Figure 7) is not associated with relaxation processes since it is independent of the conformational state of gelatin macromolecules. Rather, it is in essence a purely physical contraction of samples caused by water desorption. This contraction is completely reversible on repeated moisturing of the gelatin and correlates well with the contraction caused by decreasing air humidity at room temperature1.

(In other words, at least as I read it, changes are not structural in nature - the coil structure is maintained - but rather due to water desorption; and even this change is completely reversible).

The article is a bit to go through, but it does square with my experience in the kitchen (again - I can only speak from my experience). Intuitively, the idea that gelatin is destroyed by prolonged simmering just doesn't intuitively register with me - the gummy "lip smack" of a glace, for instance, obtained after only truly prolonged simmering, tells me otherwise.

Edited by paul o' vendange (log)

-Paul

 

Remplis ton verre vuide; Vuide ton verre plein. Je ne puis suffrir dans ta main...un verre ni vuide ni plein. ~ Rabelais

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I don't know if gelatin breaks down in a way that reduces its thickening power, but it definitely runs the risk of developing unpleasant textures when it's over reduced. When making strong reductions for glace de viande, it's possible to end up with a sticky or gluey texture in the final sauce that is not present if you use greater quantites of less reduced glace.

It's also next to impossible to get the same luxurious texture that comes from coulis thickened by multiple immersions (tripple jus, for example) but which are too expensive for most people to consider.

A bigger issue for me is the loss of subtle, volatile flavor components from extreme reduction. I tend to prefer a traditional demiglace (made with a fair amount of meat in the stock, slightly thickened with starch and moderate reduction) over highly reduced glace, for this reason.

Notes from the underbelly

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I don't know if gelatin breaks down in a way that reduces its thickening power, but it definitely runs the risk of developing unpleasant textures when it's over reduced. When making strong reductions for glace de viande, it's possible to end up with a sticky or gluey texture in the final sauce that is not present if you use greater quantites of less reduced glace.

It's also next to impossible to get the same luxurious texture that comes from coulis thickened by multiple immersions (tripple jus, for example) but which are too expensive for most people to consider.

A bigger issue for me is the loss of subtle, volatile flavor components from extreme reduction. I tend to prefer a traditional demiglace (made with a fair amount of meat in the stock, slightly thickened with starch and moderate reduction) over highly reduced glace, for this reason.

I agree with you, Paul. Not only an overreduced stock, but the rate at which it reduces matters, in my book - too fast a reduction, and the localized heating is too radical - the stock tastes harsher than is obtained when a simmering reduction is more gently pursued. Depending on what I am doing, I may do a double stock (never done a triple, for cost reasons, as you mention), or even a classic sauce from espagnole. I have found the remouillage method I've adopted from Thomas Keller's technique yields a wonderful, velvety, impeccable mother stock for many applcations.

-Paul

 

Remplis ton verre vuide; Vuide ton verre plein. Je ne puis suffrir dans ta main...un verre ni vuide ni plein. ~ Rabelais

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  • 2 weeks later...
... and making your own is worthless, because you throw away too much to spoilage.

You believe there's a problem with freezing it?

Sorry Paul, I've been on vacation. I don't know the science behind it, but it gets freezer burnt eventually, especially when reducing it's surface area into ice cubes as some have suggested. I wouldn't freeze glace de viande (or whatever you would call the way I make it), firstly because it doesn't need to be frozen when made properly, and secondly because my freezer space is at a premium :smile: .

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  • 1 year later...
I like to mix softened butter with flour in a small bowl with a whisk.  Pick up some of the mixture on the whisk and stir it into the simmering sauce.  Adds a little richness in addition to thickening.

but it interferce with the colour

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i want to know the best way to thicken a espagnol sauce or demi glace besides reducing it?

I've had good luck reducing just to the point where the flavor is right, and then adjusting the consistency with arrowroot starch (starting with 1/2 tsp per quart, made into a slurry with a bit of cool water. It thickens the sauce after a low simmer for a minute or so. Be sure to test consistency by drizzling onto a cool plate.

For my last couple of batches of demi, I've moved away from the reduced espagnole method, and experimented with modern methods that are really an update of 17th and 18th century meat coulis.

Time requirement is about the same, and food costs are lower. I like the results much more. The technique is appropriate for a glace that has a distinct meaty flavor; it will not always substitute for more neutral glaces (reduced veal stock, etc).

Recipe is here: http://recipes.egullet.org/recipes/r2081.html

Notes from the underbelly

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  • 4 years later...

I'm looking at Escoffier's recipe for demi-glace (which I'll be using as a base for his Madeira sauce). He mentions finishing the sace with 'one-tenth of a quart of excellent sherry'. What kind of sherry would he be using? Or rather, what kind of sherry should I use? A fino is going to a very different outcome to, say, an oloroso.

Chris Taylor

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