The third ingredient that I'm going to tell you today, is so called protein in sauce. There's different type of proteins. The first one is gelatin, it can be from egg yolk. Or even, it can be from cheese or yogurt. For gelatin, just try to remind you, so, you wonder where gelatin comes from. So one of the major source of gelatin is actually from the meat. And, inside the meat, if you still remember contains connective tissues. Which mostly, they are the collagen. So, so when a collagen, when we try to heat up the collagen, and the collagen if you still remember, it contains three strains of protein. And when we heat it for a long period of time. And at high temperature, this three, protein will start to unwind. Once it's unwind, it forms the gelatin, and most of the gelatin, in fact, it can be obtained from meat, from cooking meat. However, for the gelatin, it can add not only to the flavor, but sometimes it also can add to a certain thickening of the sauce we've prepared. But, however, when we try to look at most of the recipe in the sauce, what you mostly discover is whenever we use gelatin. As one of the major component in thickening our sauce. Normally they also add starch, you wonder why. So, one of the simple reason is, starch probably can serve better as a thickening compared to gelatin. But, in fact, gelatin itself can still serve as a thickening agent. But why the thickening ability is a bit weaker than starch. It's because, for the gelatin, the molecule itself. They hold so tight with each other. Sometimes, it's really hard for the water to get into the, this between the gelatin molecules. It make the so called thickening process become slower and it's not as effective as compared with starch. So, similar to, as I said, similar to starch when we can able to have prolonged heating and water can also get into some of the gelatin molecule and eventually, it become a thickening agent. But as I said, the effectiveness is relatively lower than starch because the molecule, they tango so close of each other, sometimes really difficult for water to get in. The second source of protein, what people normally use is so called egg yolk. Egg yolk, in fact, is the most cheapest and most easily available so called protein source. If we look at the composition of egg yolk, it contain quite a lot of water, over 50% and the rest of it and most of it, 16% is composed of protein. And in fact it can be readily and when we try to break it down by whisking, so it can be form a rich and creamy fluid. So, this actually we mostly use it in preparing some sauce by simply whisking the whole egg yolk into become a fluid and not only sometime. We use it as a thickening agent because it contains protein, but sometimes we have some added value, is it add more color to it. It, because egg yolk is yellow in color, sometimes it make the food become more appealing. The third one is so called cheese and yogurt. So in fact for cheese and yogurt, apart from it contains protein, in fact it also contains fat. Because fat and water they are, immiscible, sometimes when we use cheese and yogurt, they form emulsion. And some of the emulsion in fact when we try to break up the cheese and yogurt, you can see we define so called fat droplets inside your sauce. This actually come from the fat inside the cheese and yogurt. But however, since the cheese and yogurt is still contain protein. It also can serve as a thickening reagent. But for those protein, because, the protein has been stabilized, in when we try to prepare the cheese and yogurt, because it actually undergoes, so called fermentation. And the protein has gone through a really stable state. So that's why, in mostly, when we try to use cheese and yogurt, it normally won't add a new so-called thickness. Because they all been stabilized by the fermentation process. So, that's why when we try to use cheese and yogurt in preparing the sauce, that thickness is only contribute by their original thickness. But they cannot develop further thickness by itself because all the protein inside the yogurt and the cheese mostly they has been denatured. But I will get into the protein denaturing in the later. For the protein. In fact, they have different interaction in the aroma. And also the flavor perceptions. Because protein, as I said, they have a, some force that they tangle with each other. Not only they have strong force tangle with each other, they can also have some force actually bind with some other molecule like flavor and aroma. Those binding force, what we call the force is hydrogen bond, because they can bind so well with the aroma and also flavor, sometime it actually takes time for them or really hard for them to get out. So, what we end up is, whenever, we use the protein, mixed together with aroma, the flavor, in fact, once it get into the protein molecule. Sometimes, it's difficult for it to get out. So what you end up is the flavor persistence will become longer. Because it binds so tight with the protein molecule. And the flavor eventually will slowly release to our mouth. So that we won't actually sense a strong flavor. But instead of strong flavor at a short period of time, the flavor actually come to our mouth in a much gentler or in a much longer time. Now, what I'm going to show you is a typical so called egg custard, by using protein as one of the major ingredient in preparing the sauce. Zoe, firstly what we are going to do is, we try to heat up the pan. And the protein mainly, firstly, is come from milk. This is the continuous phase of our sauce. Here what we have, we have egg yolk as one of the protein source and we have sugar. And what we are going to add is we need to have flavor. That is vanilla, so we have a vanilla flavor. So, as I mentioned, even though we put flavor. It won't actually give a strong flavor. Because here, we have protein. Protein can bind the flavor really tight. So that the flavor won't suddenly go out in a really short period of time. Instead, it, it will become. Coming out is a really long period of time. So it's actually become a certain consistency there. After, it reach to a certain consistency. Yeah, pour the whole thing away. Right, okay, and then we pour it back right, okay. So, and then we stir it, okay. We simmer it for a while. It, yeah, becomes a, yeah. It's very thick. Okay, yep. So, mm, let me try it. So it's much thicker than the egg itself. Mm. It's really delicious. I can smell a really intense vanilla flavor together with egg.
