other to form brown pigments and a host of new flavor molecules (p 778) But if the juices remain juices, they constitute a very basic sauce, a product of the meat that can be added back to moisten and flavor the mass of coagulated muscle protein from which they’ve been squeezed The problem is that the meat or fish only gives up a small amount of juice compared to the solid mass To satisfy fully our appetite for those juices, cooks have invented methods for making meat and fish sauces for their own sake, and in any quantity The main thickening agent in these sauces is gelatin, an unusual protein that cooking releases from the meat and fish Cooks also use other animal proteins to thicken sauces, but their behavior is very different and more problematic, as we’ll see (p 603) The Uniqueness of Gelatin Gelatin is a protein, but it’s unlike the other proteins that the cook works with Nearly all food proteins respond to the heat of cooking by unfolding, bonding permanently to each other, and coagulating into a firm, solid mass It turns out that gelatin molecules can’t easily form permanent bonds with each other, due to their particular chemical makeup So heat simply causes them to shake loose from the weak, temporary bonds that hold them together, and disperses them in water Because gelatin molecules are very long and get tangled up with each other, they give the mixture a definite body, and can even set it into a solid gel (p 605) However, gelatin is relatively inefficient at thickening Its molecules are very flexible, while those of starch and other carbohydrates are rigid and better at interfering with the movement of water and each other This is one reason why gelatin-thickened sauces are usually augmented with starch A sauce that contains only gelatin requires a large concentration, ... form permanent bonds with each other, due to their particular chemical makeup So heat simply causes them to shake loose from the weak, temporary bonds that hold them together, and disperses them in water... molecules are very flexible, while those of starch and other carbohydrates are rigid and better at interfering with the movement of water and each other This is one reason why gelatin-thickened sauces are usually...proteins that the cook works with Nearly all food proteins respond to the heat of cooking by unfolding, bonding permanently to each other, and coagulating into a firm, solid mass