It's a sad fact that these days it has become almost essential to marinade most cuts of meat, unless you intend to casserole them. I'll go into why that is the case a bit later on, but for the time being let's just examine why we use marinades at all. Principally there are two reasons. One is to add flavor, and the other is to tenderize. Usually, we are trying to do both.

It's worth bearing in mind that marinating is a cooking process, even though heat is rarely applied. The importance of recognizing this is that, like any other cooking process, you can overdo it. It's not just a case of putting the meat or fish in a sauce and leaving it there until you are ready to use it. Many of the fruit juices we use in marinades, such as lemon and pineapple, contain enzymes that break down proteins. In essence, what they do is digest them.

Leaving meat in them for too long would result in an unpalatable mush. If you want to try this for yourself, leave a piece of pork in fresh pineapple juice overnight and then see what happens when you cook it. You probably won't like the result. Why is meat tough?

It's a tragedy that although we are killing our animals at an earlier age in order to satisfy the demand for fresh meat, the end product still tends to be tough. There are good reasons for this, and it is useful to have a working knowledge of them if only to avoid potential disasters.

It is not, as some cooks would have you believe, simply a matter of finding a butcher who will take the trouble to discuss your needs with you, if indeed such a person still exists outside of the more fanciful cookbooks. Our meat is tough because it started out that way. And here's why: