Facts and fiction about food and cooking, by Peter Aitken
Many people believe than an acidic marinade – one containing wine, vinegar, or citrus juice – will make meat tender. In fact, the opposite is often the case. Acid interacts with the proteins in the meat, causing the protein molecules to pack more closely together and thus squeezing liquid out of the meat. The result? Tough and dry steak, chicken, or what have you. What’s more, extended exposure to acid can cause the surface of the meat to become mushy because the proteins start to break down. The rule, then, would be to keep acidic marinade periods short, but then of course the flavor won’t get into the meat very well. My approach is to rely on non-acidic marinades.
The fact is, marinades in general don’t have nearly the effect that many people think because the flavors just cannot penetrate beyond a millimeter or two at the surface. Salt and water in a marinade can penetrate deeper, and the benefit of most marinades is the result this factor.
Kitchen Myths 
“The acid in marinades does weaken muscle tissue, and increases its ability to retain moisture”
p155, On food and cooking, by Harold McGhee
Whats you’re source evidence for this controversial claim?
My source is “The Science of Good Cooking” from Cook’s Illustrated. As much as I respect McGee, I think he is wrong on this one – as borne out by my own experience.
I grew up eating Sauerbraten, which is a German beef dish marinated in vinegar and spices for up to a week. I remember my father making it with tough cuts of meat that would come out extremely tender after he marinated it for so long. The meat would literally melt in your mouth, similar to how lamb in Indian dishes comes out. If the marinade wasn’t making it tender, what was?
Good question about the sauerbraten. Let me look into this further and I’ll post if I find out anything.
I got some more information on the acid marinade / sauerbraten question. It turns out that whatever effect the wine and vinegar marinade has is limited to the surface of the meat because, other than salt and water, the components of any marinade just don’t penetrate the meat very well. The tenderness of the sauerbraten has nothing to do with the marinade but rather with the long slow cooking, just like with unmarinated meat.
Thanks!
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