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Is it scientific fact that acid stabilizes meringue or is this a fallacy? If so does anyone know actually why and are there any other substances that do this well also?

Sebiddychef
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    Yes it is true. A very related question: http://cooking.stackexchange.com/questions/16210/why-do-my-egg-whites-separate-after-whipping (note that acid also denaturates proteins) – nico May 23 '12 at 07:27

2 Answers2

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Acids allow more air to be beaten into a meringue. In order to make meringue, the proteins in egg white must be denatured. In their natural state, the proteins are curled up into tightly packed balls. When the egg is beaten, they uncoil into long strands.

These strands then begin to coagulate, or join together, with the help of the sugar you add. The air you whisk in gets trapped between these joining strands, giving the meringue its characteristic light texture.

Acid delays coagulation, which means that there is more time for air to get trapped in amongst the proteins, resulting in a lighter meringue.

The acids usually added to meringue are white wine vinegar, lemon juice, or cream of tartar. Fresh eggs are more acidic than old ones, so these help too.

Some cooks use copper bowls to make meringue, because copper ions from the bowl bind to a particular protein (conalbumin) and strengthen it.

Basil Bourque
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ElendilTheTall
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    @Elendil- do you have a reference that I could look at? I know acid helps denature the proteins faster but I have never heard that they delay coagulation. – Sobachatina May 23 '12 at 14:33
  • http://highered.mcgraw-hill.com/sites/0078616441/student_view0/food_science_activities/demystifying_meringue.html or http://procrastibaking.co.uk/2011/06/01/the-biochemistry-of-lemon-meringue-pie/ – ElendilTheTall May 23 '12 at 14:47
  • @ElendilTheTall thanks but (I'm probably wrong) I thought that egg whites were alkali? – Sebiddychef May 23 '12 at 17:48
  • They are slightly alkali, but they are less so when they are fresh. Less alkali = more acidic :) The relative weakness of the acids used to tip the pH towards acidity are testament to the mildness of the alkalinity. – ElendilTheTall May 23 '12 at 18:19
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    I'm 90% sure that your references are unreliable; acid *promotes* coagulation, that's why people add vinegar to poached eggs (you can watch it for yourself and see how the whites coagulate almost instantly when the water has been acidified). And in my experience, acid makes a meringue firm up much faster (once you hit the foam stage you're basically just coagulating very slowly). – Aaronut May 24 '12 at 00:31
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    Research source: [On the "Heat Coagulation" of Proteins](http://jp.physoc.org/content/40/5/404.full.pdf): "Halliburton (1884) found in the case of serum albumen that neutralizing (to litmus) an alkaline solution lowered the coagulation temperature from 80° to 78° C. and, by the successive addition of small quantities of acid, it fell as low as 53° C." Maybe the chemistry of a chicken egg is different, but I doubt it. – Aaronut May 24 '12 at 00:47
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    Well, damn my sources for a pack of greasy dogs! – ElendilTheTall May 24 '12 at 06:01
  • Actually I think ElendilTheTall and @Aaronut are both correct. Coagulation of some proteins is what forms the meringue in the first place; but coagulation of others can make it collapse. An egg foam needs to have the proteins bonded tightly enough to form a stable structure, but not so tightly that they squeeze out air and water and collapse. Acids encourage coagulation via the weaker bonds that hold the structure, and discourage coagulation via the stronger disulfide bonds that would collapse it. – csjacobs24 Jan 21 '22 at 21:55
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I have made two separate meringue mixtures side by side: one with vinegar and one without. In my experience it makes no difference to the final outcome provided that you add the sugar really slowly (a tablespoon at a time) and not too early. If this is done correctly then there is no need to add an acid.

Sebiddychef
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scottishpink
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    Define "final outcome". Time to soft peaks? Time to stiff peaks? Stability when raw? Stability after baking? Were the quantities of ingredients measured reasonably precisely and incorporated using a consistent and repeatable method? This answer gives the impression of being based on experimental data but it's unclear what, if any, controls were used. – Aaronut May 24 '12 at 00:35
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    wow I am not a scientist just a busy mum who experiments with what ingredients are necessary, sorry for any confusion. "Final outcome" meant they look, taste, sound and eat the same !!Should prob not added my comment to such a professional and scientific question. – scottishpink May 24 '12 at 03:56
  • I'm with you, whether they taste the same is an important measure! But it's not very useful on this subject, because the point of the acid is to make it less likely that your meringue will collapse. Often a meringue will hold up fine without acid, and when it does it'll taste the same as one with acid. So you can't just make both and say that since they taste the same the acid didn't help. You'd have to make both several times and see if the acid-free one collapsed more often. – csjacobs24 Jan 21 '22 at 21:19