The content of a fruit in fact is going to change the texture a lot. Let me demonstrate that to you. I have two kiwi fruit. Okay, so it's here. one is ripe and the other one's not. Let me try it out. This one Hmm. Okay. I'm going to try to like, take some of it out. It's not as easy. How about the other one. Much softer. I'm going to try to take something out. Easily I can put my spoon into it. Now. So, what happened? In fact for the right fruit, the texture of the fruit is quite different because they have a lot of sugar, solution in it, and also the cell will actually, they are much soften. So therefore, this sugary solution where the succulent kind of like impression. We call that a very melty type of appearance. Now, in fact, we always associate that with fruits; such as, mango, kiwi and pear, right. So, therefore, substance inside a particular vegetable or fruit, is going to, in fact, change the texture. Now for example, potato juice/g. Potato, in it, there are a lot of grainy substance in it. That in fact, that is the starch. What happen is that if you have just a potato, you purchase it from the market, actually they are pretty tough. We have some potato here. Yep, pretty tough. But you'll find that, after you have cooked them, in fact, some of these starch granule, they become like a soft and they aggregate together and become a little bit mushy. And of course, if you wanted to be very like crispy also, you can prepare it into potato chips. So, definitely, they can be of different kind of texture. And that is depending on the starch granules in them. So in raw vegetables these starch granules, usually they're very hard. And so therefore when they're packed together they become very granular. This chalkiness of, of texture that you, you sense in fact is the starch granules. Now. The interesting thing that as I pointed out, as you try to cook them a little bit, at, 50 to 60 degree, you'll find that in fact, these kind of starch granule, they will start to swell a little bit, soft water and what they found is some sort of gel like structure. And they're gel like; therefore, they're much softer. You don't sense the same kind of granule and they form some sort of a sponge on sopping water. And in a way, that give you the tenderness, or meshy type of like a feeling. So, therefore, the change of temperature can change the texture. Now, of course, you can continue to do that with when you cook. initially at the wrong temperature, all the plants or vegetables. They have their cell wall more or less intact. But then when you raise the temperature to 60 degree, what you have is that the cell membrane, they would be damaged, so some of the material inside would be released. And the cell start to lose water, and they start to deflate and become very flaccid, and at the end, they are no longer as rigid as original. They are, they become a little bit more chewy. Why chewy? Because a lot of time they still have fiber in them. But if you continue to, cook them, and increase the temperature, or you boil them for a while, you find that well, all these cell walls disintegrate. They are totally destroyed. They become weakened so much that. Well, all this cement that links all the cells together, they're broken down. So what happens? This is something like that. It's like a puree, right? So, ti's like a suspension of all this plant substance. Together like a paste. Now, having that, so we wonder. Well, what other factors can change the texture? Would the pH of water affect the texture of fruit or even vegetables? Let me show you something. Which is in fact a lot of these fruits they are being bind together by some of the same manners that link them together. And these are sometimes the hemicelluloses, they are not very soluble in the acid condition, but however if you change it to the alkaline condition They will start to melt away. So let me show you something. So this is a, diagram of some vegetable, this is it's choy sum. This choy sum we simply cook it in tap water. I want you pay attention two thing. One is this popular choy sum in fact is and you pay attention to the color of the plan as well as the medium what is this one,this one is we cooked in tap water for five minutes ,how about the next one,the next one is like this,so you find that by the choice of stew rather to be intact Pay attention at the medium. The medium is much lighter in color. What happened to it? In fact, it is cooked in the vinegar for five minute. But, how about the third one? The third one, well, it's really like a soup. So, you look at that. Well, the can you still recognize what the is like? It's somewhere here and the medium is very dark green. So what happened to it, in fact, we cook it in baking soda for 5 minutes, so what's the difference? Tap water, we all know that from most of the city, tap water is usually a little bit alkaline, alright, a little bit. But if you put it in vinegar, it is a relative acidic. That means it, as we call it, pH is much lower. But when you put in baking soda that gets rid of the alkaline. So I want to show all this plants to you again and see actually how they look like. So this one we cook it in tap water. Look at what happened. So basically the plant is still relative intact, relatively green. Okay. How about the next one? This one. So this is the one that we cook it in vinegar. You notice that it's still relatively intact. Okay, but pay attention to the color. The color seems to change a little bit. We're going to cover that a little bit later. How about the third one? This is the one that we cooked in the baking soda. I hope that you can still recognize it. Well, this is the one which we cook in baking soda for five minute. So basically they're so mushy that I can't even tell that is a vegetable. And the solution the, the medium that we use to cook it is relatively green. But even for the vegetable, it's still green. Okay. Now, having that in mind, we say that in fact we can use this particular property. We can play around with it and say determine how we want to cook vegetables. Sometimes we say, whoa, whoa, if I don't want to put it in the water or medium to cook it, can we cook it some other way? Yes. we can steam it, we can fry it or we can bake it, but in all these cases, what happened? We don't have a medium surrounding this particular vegetable. So, but remember when we cook them, this plant is start to disintegrate. So the membrane will be broken. And so therefore whatever inside will be released. Remember what I said? Inside, that's the vacuole. The vacuole usually is slightly acidic. So therefore, this acidic would come out. So therefore, what happen is that. The acid when it comes out, it doesn't really change anything about the or the cements that have to glue all this together. So therefore the plant would still be pretty good looking.Okay. Except the color. I'm going to talk about that later. Now. What happens, in fact we notice that the presence of some of the ions, they are also playing a very important role in changing the texture of these plants. For example we say that the calcium, well having the calcium there would slow the softening of all these plants. Why is it Remember that I said that these plants out they need to use the glue them together and what happen is that calcium is a very essential ion to help to make this semen work very well. So therefore it will put a lot of the calcium there, they are going to stick together much better so that means it stick together much better. They are not going to dissolve away. Or to be separated or disintegrated. So what happens that when you have calcium, they usually, they would be tougher, little bit stiffer. On the other hand, if you add a little bit of salt, sodium chloride, table salt, what happen is that table salt is going to compete with the calcium for the same binding of all the cement. So, it kicks out all the calcium, so that the association between the plant and cell become less tight and as a result this sodium displacing the calcium ion would make the cell wall and the cement weaker. So, therefore, what happen? They would dissolve away much more easily. Okay. So, adding different kind of ion makes a difference. Now, so therefore, when we are cooking there are things we need to pay attention to Do you want to cook it, where hard water those you collect it from wells. Also, these would rich in calcium. When they're rich in calcium usually when you cook the plants would stuck together, you know, more firm appearance. or you could shorten the softening time by adding a little bit of sodium salt. Then they would be softer much faster. Now, so with that we also say that sometime for some of the vegetables, in fact we would like to use approach which is called precooking. This precooking refers to we take some of these fruits or vegetables. We raise the temperature to 55 to 60 degree. For a while, why do we want o do that? And we find that once you do that in fact, those vegetables, they can stay firm for a longer time. What happened to that? Is that in fact we notice that in the virtue of mode they do have some enzymes. These enzymes is going to be acting to help to glue the cells together and they would be activated only at this temperature about like at 50 degrees. And at that temperature if these enzymes are activated; so that means they help to glue the cells together to make them firmer. And after they have done it, even though you continue to cook them to a higher temperature they will be stuck togther permanently. So therefore the firmness can be maintained. And at the same time remember if you cook them to 50 degrees some of these cells they would be Killed and when they're killed, the vacuole sometimes they will release calcium and the endoplasmic reticulum, they also release calcium. This calcium further strengthens a sensation of all this cement. And as a result by this pre-cooking you basically preserve the firmness of the vegetables. Now don't forget that in fact we commonly we have also another type of plant that when we eat them, you notice that no matter how long you cook them, they are still very crunchy. What kind of plants are they? These are such as the, the water chestnuts, the lotus roots, the bamboo shoot, or so. These kind of fruits, you can cook them for hours. They still, they are very crunchy. So what happened to them? So they look very different, they belong to different classes of plants. But it turns out that, again, enzymatic reactions play a very important role. Because all these vegetables or, or, or fruits what they have is they have something which is called phenolic compound. Phenolic compound they are present in the cell wall so what happen is that when these in the cell wall this phenolic compound such as a ferulic acid they will form bonds were off the cell wall carbohydrates, so what happen is that help to stick them together very well and prevent them from being dissolve away So as a result when you cook them, these kind of fruit, even though you cook them for a long time, they stay stuck together to maintain the original texture. Now with that, essentially I tell you about how the texture can be changed because of the pH. Because of the various enzymatic reaction in, in them. And also of course very importantly, it depends on what kind of vegetable you're talking about. And you need to understand the basic features of these fruits or vegetables.
