After learning about our, how our endocrine system and our nervous system help us to perceive the quality of food. Let's look at a particular situation, which is when we're stimulated by the same kind of food again and again, we develop something that's called sensory-specific satiety. Why do people develop such a sense when they are exposed to the same food again and again, and again gradually they lost interest in eating it anymore? Now, in fact, there have been different kind of hypotheses suggesting that how it takes place. Some people would suggest that it's because of the need of calories goes down. when we're eating the same kind of food, we basically keep on gaining more nutrients, and so therefore, we no longer need the nutrients for the energy, so therefore, we don't like it as much. Sometimes we say that well, there are other minerals, macronutrients that they are no long needed, so we develop this sensory-specific satiety. But I think that from all the experiments done in the past, what we learn is that there are two main factors. One of the factors is related to the amount of the food, or the volume of the food. The larger it is, in fact, you get sensory-specific satiety very quickly. The next thing is because of the amount of sensory stimulation. Think about that, if you are eating something which is sweet, I constantly give you sweet food, again and again, and again not necessarily, because of the amount, is because of the stimulation. The repeated stimulation is going to generate some sort of like desensitization. Then you lost interest in it, so therefore, the focus is the following. The volume and the amount of stimulation and the food. That is going to result in sensory specific satiety. Now, we would ask how the consuming of the one food would affect the pleasentness of the other. And in fact, if you understand how the sensory specific satiety comes in to places then certainly you would understand why sometimes when we're eating something sweet. And then you eat something which is not exactly the same food, but then if it's still sweet you've lost interest in that and you don't want to eat that anymore. Because they have the same kind of stimulation, and also sometimes we say that when the food will have the same kind of texture. Lets say if they're very soft. You constantly eat something that is very soft and very jello like again and again and again. Over time we repeat this stimulation results in sensory specific satiety. Now, that in fact is very important. We ask, when we develop that, how this response, this hedonic response, is going to be generated. We say that, well, can we simply stimulate your sensory input with or without ingestion. What are the two? Sensory input sometimes is coming from the tongue, coming from the nose. But when you ingest sometime it's in your throat so that's a different place being stimulated. And sometimes when we learn about whether a food is good or bad, we also think about what's behind the food. What's the knowledge about how the food is being prepared. That again is stimulating a different perception. And sometimes, of course, when we eat the same thing again and again, I can't eliminate the possibility that because, that we are no longer in demand of the energy or the nutrients. So the interest or satisfaction that we would obtain is much less. Now, we ask if that's the case, would there be any food which is, they taste so good, they would be resistant to any sensory-specific satiety? I guess, it's very unlikely, because we know that in all the sensory input that we obtain. In fact, all the sensory receptors that we were talking about a bit earlier, they were being stimulated, but then gradually they become desensitized. So, what happen is that sometime some food, if it tastes very good, it may take them a little bit longer to get desensitized and you lost interest in them. And some food, if they're not tasting very good, maybe they develop the sensory specific satiety a little bit earlier. Now, having that in mind, it reminds you of one thing. When you're preparing food, the most important element of it, we want to generate variation of flavor. We want to generation variation of shape of the food. We want to generate variation of the texture of the food, the appearance, and sometimes we want to use different material. All this, essentially, is talking about when more of these properties are being provided in the stimulations. We would have more satisfaction coming out of it. It enhances the quality of food. So what I mean is that there are two aspects. One is physicologically. that means we have more of senory organ being stimulated at the same time. At the same it has another element of it, which is about the nutritional input. It is instinct, it built evolution, that's why we want to have different texture at different taste. Because different taste stands for they represent different kind of nutrient. So more stimulation, that means we are capturing a lot of important type of nutrients. So therefore, it is good, isn't it? So that's what they say. This is a very important strategy for survival, because having this variation of stimulation means that we will have more energy intake, because there are more nutrients of different shape and form and taste and smell they are coming to us. So, we would able to maintain some sort of like a nutritional balance. Now, take that into mind even though we are not really aiming for getting this nutritional balance when we are preparing a meal, but then it help us to do the meal planning. So take for an example using a famous Chinese dish called Peking duck. We want to introduce idea that we want to increase the so called contrast to have more ingredients that can stimulate our sensory input. In this case, in the peking duck look at what is in the peking duck. The peking duck is not just a duck. What a Peking duck has is that we would have a duck. Usually they are a little bit of fat so they need to have fat underneath the skin, and they have meat. So, certainly and when they are roasted like this they have a very specific color. What other things do we add? We have the dough and it depends on different restaurants. Some of the dough are much softer or thicker some, some are harder and we have the, the, the onion, sometimes we have cucumber and all this together with the sauce. Now combined together, what do we do? When you eat them, you cut a piece of this duck with the skin, together with the fat and some meat. What do you do? You wrap them into the dough and you put the crispy cucumber and you put the sauce. What are you experiencing? It's something like this, and then you eat them all in one mouth and put into your mouth and you, what do you sense? You are sensing a variation of texture. You are sensing a variation of temperature. The duck is hot but the cucumber is cold and the taste You have the taste of the sauce. You have the taste of the cucumber. You have the taste of the meat. You have the taste of the skin, which is crispy. At the same they have a different texture. The cucumber is a bit crunchy, and the fat, they would be very soft. the meat maybe a little bit tender. So, at the same time, you combine all these in one single bite. That gives you the maximum stimulation of the sensory input. And that's why you find Peking duck is very tasty. And in fact, in the following we can do experiment with our students and see actually how they perceive this sensory specific satiety. And that will tell us how come sometimes you don't want to eat certain food and sometimes you want to eat more.
