I know the Maillard reaction to cook at 140–160 °C. I know the low temperature cooking reaction to cook at 70 °C. But which is the reaction that allow us cooking meat or fish with vinegar or lemon juice?
Apparently this question has been covered on the Cooking SE site - in this post, it is reported that:
The Oxford English Dictionary defines to cook as:
To prepare or make ready (food); to make fit for eating by due application of heat, as by boiling, baking, roasting, broiling, etc.
However, from a chemical point of view, what happens when you are cooking meat is that you are using heat, amongst other things, to denature the proteins of the meat. Denaturation can also be achieved by other means, such as marinating the meat in an acid, such as citric acid (contain in lemon juice) or acetic acid (contained in vinegar).
You can also use other agents to induce denaturation, but they are not always fit for eating.
However, it is important to understand that from a purely cooking perspective the two things are not the same: "cooking" with lemon (I guess it is fine to use the verb to cook as long as you put it in quotes), gives a completely different result than cooking with heat. This is because other chemical reactions happen during application of heat and because, obviously, you do not end up with an hot product!
which indicates that the application of acidic media to meat accomplishes the act of denaturing proteins therein in a way mechanistically similar to what cooking with applied heat does.
From Kitchen Daily:
Acids like lemon juice, lime juice and vinegar break down raw meat, allowing the marinade's oil and spices to deeply penetrate and infuse the meat with flavor and moisture. They dig out little pathways in the meat and allow the marinade to seep in. The scientific term for this breakdown is "denaturation," which is the process in which protein loses its structure by application of a strong acid, base, salt, alcohol or heat. Basically, the scientific process that cooks meat with heat in the oven is the same one that cooks it with acid. The results may taste a little different -- fish cooked in the oven is flaky, whereas fish cooked by lemon juice (a.k.a. ceviche) has a more raw-tasting consistency -- but the process is the same.