95 The Science of Baking-Mid

The Science of Baking FOCUS Question What are the physical and chemical changes that take place during baking?

烘焙过程中发生了哪些物理和化学变化?

Oven Chemistry Mmmmmm! Don't you love the smell of something delicious baking in the oven? Believe it or not, gooey cookies, fluffy cake, and warm bread are all made using chemistry. When a baker mixes together the right ingredients in the right order, the atoms inside start to interact. Each ingredient has a task, and once heat is added, a blob of batter transforms into a tasty baked treat. Let's find out why these kitchen chemical reactions taste so good!

烤箱化学呣呣!难道你不喜欢烤箱里烤东西的香味吗? 信不信由你，黏糊糊的饼干、蓬松的蛋糕和温暖的面包都是用化学物质制成的。 当面包师按照正确的顺序将正确的食材混合在一起时，里面的原子就开始相互作用。 每种食材都有一个任务，一旦加热，一团面糊就会变成美味的烘焙甜点。 让我们来看看为什么这些厨房化学反应味道这么好!

Mixing It Up Let's bake a cake! Combine the dry ingredients, or reagents—flour, baking powder, and salt—into a mixture. Separately, mix the butter and sugar. The sugar doesn't dissolve, but it spreads evenly throughout the butter. You have created a colloid. Add the dry mixture to the colloid and then blend in the eggs, milk, and vanilla. Now you have a thick solution. Mixtures, colloids, and solutions are all the result of physical changes. Some physical changes are easy to undo, like picking raisins out of trail mix. But with cake batter, you can't easily separate the ingredients once they are combined. This kind of physical change is what allows bakers to create something new, like a cake!

让我们烤个蛋糕吧!将干燥的原料或试剂——面粉、泡打粉和盐——混合成混合物。 分别将黄油和糖混合。 糖不会溶解，但会均匀地分布在黄油中。 你已经创造了胶体。 将干燥的混合物加入胶体中，然后加入鸡蛋、牛奶和香草。 现在你得到了浓稠的溶液。 混合物、胶体和溶液都是物理变化的结果。 有些身体上的变化很容易消除，比如从什锦干果中挑出葡萄干。 但对于蛋糕面糊，一旦它们混合在一起，就不容易分开。 这种物理变化使面包师能够创造出新的东西，比如蛋糕!

A Sticky Framework Like the frame of a building, a cake needs a structure, or framework. Without it, the cake will collapse into a pile of crumbs. Gluten, a protein substance found in wheat flour, provides that structure. When the flour gets wet from the milk and eggs, two proteins join to form long strands of gluten. Mixing the batter creates even more gluten, which holds everything together. Gluten molecules have links between them that hold them together and make them elastic, or able to bounce back. This property allows cake and bread to rise, but too much gluten can result in chewy bread or dense cake. Not so yummy! To prevent this problem, bakers use flour with the right amount of protein for their bread or cake recipe, and they don't overstir the batter. glutenin + gliadin = gluten When the two proteins in flour—glutenin and gliadin—get wet. they unwind and join together to form gluten. Think About It If you have ever tried to stretch out pizza dough, you know that it springs back when you let go. Why do you think it does that?

就像建筑的框架一样，蛋糕也需要一个结构或框架。 没有它，蛋糕就会碎成一堆面包屑。 麸质是小麦面粉中的一种蛋白质物质，提供了这种结构。 当面粉被牛奶和鸡蛋弄湿时，两种蛋白质结合在一起形成长链面筋。 混合面糊会产生更多的面筋，把所有东西都粘在一起。 面筋分子之间有连接，将它们连接在一起，使它们有弹性，或能够反弹。 这种特性可以让蛋糕和面包发胀，但过多的麸质会导致面包有嚼劲或蛋糕密度大。 不太好吃!为了防止这个问题，面包师使用含有适量蛋白质的面粉来制作面包或蛋糕，而且他们不会过度搅拌面糊。 当面粉中的两种蛋白质——谷蛋白和麦胶蛋白——变湿时。 它们会散开并结合在一起形成面筋。 如果你曾经试着把披萨面团伸展开来，你就知道当你放手的时候，它会弹回来。 你觉得它为什么会这样?

Rising Up Now you have a solution of batter with gluten ready to provide a framework. But your batter is still a bowl of goo. To get an airy cake or other baked goods, you need bubbles in the batter in order to expand the elastic gluten framework. Cookie dough uses the properties of butter to create some of the bubbles. Butter is an emulsion—a glob of water fat and solid dairy products all stuck together. Inside the hot oven, the butter in your cookie dough melts. The dough flattens out, and the water in the butter separates from the fat and dairy. The water molecules turn to steam, forming bubbles that make the cookie dough rise slightly.

现在你有一个面糊溶液和面筋准备提供一个框架。 但你的面糊还是黏糊糊的。 为了做出通风的蛋糕或其他烘焙食品，你需要在面糊中加入气泡，以扩大弹性面筋框架。 曲奇面团利用黄油的特性制造出一些气泡。 黄油是一种乳剂——一团水、脂肪和固体乳制品粘在一起。 在热烤箱里，饼干面团里的黄油融化了。 面团变平，黄油中的水分从脂肪和奶制品中分离出来。 水分子变成蒸汽，形成气泡，使饼干面团微微膨胀。

Heavy Lifting The real heavy lifter in baked goods is called a leavening (LEH-vuh-ning) agent. One of the chief leavening agents is baking soda, or sodium bicarbonate. Even before you place the cookie dough into the oven, the sodium bicarbonate begins to react with acids in the dough and creates carbon dioxide gas. In the oven, this reaction speeds up. The gas expands, opening air pockets in the gluten structure. This chemical change causes the dough to rise. It is impossible to reverse this step. Baking powder—baking soda mixed with an acid— is often used for cake batters that don't already have acid in them. It makes carbon dioxide gas as soon as it contacts the other ingredients, and it reacts further when heated in the oven. Lots of carbon dioxide gas bubbles create a fluffier cake!

在烘焙食品中真正的重量级提升剂被称为发酵剂(LEH-vuh-ning)。 一种主要的发酵剂是小苏打或碳酸氢钠。 甚至在你把饼干面团放进烤箱之前，碳酸氢钠就开始和面团中的酸发生反应，产生二氧化碳气体。 在烤箱里，这个反应会加速。 气体膨胀，在面筋结构中打开气囊。 这种化学变化导致面团膨胀。 这一步是不可能逆转的。 泡打粉-小苏打和酸的混合-通常用于蛋糕面糊中不含酸。 一旦接触到其他成分，它就会产生二氧化碳气体，在烤箱中加热时，它会发生进一步的反应。 大量的二氧化碳气泡创造了一个更蓬松的蛋糕!