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The third chapter Baking & Cooking covers the chemistry and science behind of baking and cooking processes.

Baking

There are many ingredients that can be varied for different flavour and textures of baked goods, from cookies and breads, to macarons and cakes. I will be focusing on breads as it is the simplest baked goods to discuss in detail here. There are 4 general factors to making breads:

1. Flour & Water
   The ratio of flour to water ratio determines what is it called. If the mixture is predominantly flour, it is a dough. If the mixture is predominantly water, it is called a batter. Doughs are used for making breads while batters are used for making crépes, and griddle cakes (pancakes).When the flour is mixed with water and kneaded, the randomly oriented glutenin molecules forms a network of gluten chains. Repeated kneading helps to stretch and elongate the gluten chains by forming strong chain end-to-end bonds. This produces a stretchy and elastic final product. If the dough is over-kneaded, the dough becomes sticky and inelastic.Kneading also introduces air into the dough by forming small trapped air pockets. The more pockets formed, the finer the texture of the final bread.
2. Salt
   Salt is added 1.5-2% of the flour weight, to help tighten the gluten network and improve the final volume of the loaf. The sodium and chloride ions cluster around the charged regions of the glutenin proteins, preventing them from repelling each other.
3. Leavening agent
   There are 2 types of leaveners, microbiological (yeast) and chemical. Yeast consumes sugars in the dough to produce carbon dioxide in the gluten network, forming small air pockets and increasing the volume of the dough (refer to my post on fermentation, on how yeast works). Doughs using yeast for rising would need to incubate the yeast in a warm environment for a few hours before baking the dough.The other method is chemical leavening. No, it’s not something artificial and unhealthy. It works via the chemical reaction between an acid and a carbonate (a base), which releases carbon dioxide. Baking soda is chemically known as sodium bicarbonate (NaHCO3), which would react with an acid such as buttermilk or citric acid. Baking powder is a mixture of sodium bicarbonate and tartaric acid (cream of tartar; can be found naturally in fruits such as grapes), which only requires water to initiate the acid-base reaction. Much simpler, eh? However, that depends on what ingredients the baker wants to use.

Of course, nonetheless we have the actual baking process where the magic happens. When introduced into a pre-heated oven, the moisture within the dough vaporizes and the dough expands and rises. After 6-8 mins, the gluten molecules would start to form strong cross-links and forms a rigid structure that does not stretch. The air pockets within the rigid structure can no longer stretch and would rupture forming the open network of pores that you see in the final product. Over time, continued baking would result in surface browning, forming the bread crust and develops the flavour. This process is also known as the Maillard Reaction (covered in the next section; read on!).

That’s a summary of how bread is made! I wish to talk more in detail about other baked goods but it will be too long.

Fun fact: Biscuits and cookies can become soft and ‘airy’ if not stored properly. This is due to the absorption of moisture from air by the sugar in the biscuit. This can be reversed by toasting or baking it at a sufficiently high temperature and time to remove the moisture within.

How you say? Let’s talk about cooking methods.

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Cooking

As a Chemistry major, we learnt about the interactions between the electromagnetic radiation and molecules. Scientists uses these intrinsic characteristics based on quantum physics and chemistry to investigate the structures of compounds of interest. On the other hand, we use it everyday to prepare and cook food.

Don’t be intimidated by the diagram 🙂 As you might remember from your science classes, atoms and molecules rotate and vibrate in the fixed positions. When the energy of the electromagnetic radiation coincides with the required energy, the molecule absorbs the energy and achieves a higher energy state, similar to fitting a key in the right keyhole. The molecule would then relax and release this energy in the form of heat. This is why your frozen food would heat up after spinning around in the microwave. Generally, what would be commonly used for food preparation are microwaves and infrared radiation.

Microwave radiation coincides with the energy for molecules to rotate, while infrared radiation coincides with the energy for molecules to vibrate. As chemical reactions occur between molecules when their bonds break and form new bonds, they would first need to stretch beyond its limits and snap apart. Infrared energy is responsible for this process and can be observed while barbecuing food, where hot burnt charcoal releases heat in this form. (This is due to a phenomenon called the Blackbody Radiation). However, chemists would understand that only polar molecules would absorb infrared energy.

This is a good time to transit into the cooking processes. Moving on!

Processes

Caramelization

Caramelization is the process where any sugar (glucose, fructose, sucrose, etc.) are heated and the structure starts to break apart. The broken sugars form hundreds of new compounds of varying taste and aroma. The longer a sugar is cooked, the less sugar and sweetness remains, the darker and bitter it becomes.

(Insert glucose, fructose and sucrose molecules)

Glucose and fructose are referred to as “reducing sugars”, in which they are easily oxidized and reduces other compounds, making them more reactive. Sucrose is made of 1 glucose and 1 fructose molecule bonded by an alcohol group, hence making less reactive than its constituent sugars. This is why sucrose requires a higher temperature for caramelization (170 deg C) than glucose (150 deg C) or fructose (105 deg C). This is the same process occurring when the cookbook or video asks you to caramelize your onions.

 

Maillard Reaction

The Maillard Reaction occurs between a carbohydrate (a sugar) and an amino acid, forming an unstable intermediate product before further forming hundreds of different by-products. A brown colouration and full, intense meaty flavour will be produced.

Maillard flavours are more complex and meaty than caramelized flavours (in the next subsection) due to the involvement of amino acids containing nitrogen and sulfur atoms, introducing whole new possibilities for new families of molecules.

This is the process occurring during the cooking of meat at barbecues, where Maillard reactions can take place temperatures below 100 deg C. Thus, in general, Maillard reactions occurs at lower temperatures, while caramelization starts at higher temperatures.

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Workshop

This week, we had a self-directed Pancake workshop. There were two pancakes, one souffle and one western. Both similar in their ingredients but their amounts varied.

The goal was to observe and investigate the role of ingredients, the amount of ingredients, and the preparation process. My group got the western pancake recipe, which was significantly easier than the souffle style. The souffle style would required to foam egg whites till peaking is observed. A foam is essentially gas (air) dispersed through a liquid (egg white). This allows the final souffle to have a light, fluffy mouthfeel after the pancake batter solidifies.

As mentioned earlier, baking powder is added to allow carbon dioxide to be produced without a need of an additional acidic ingredient. This also introduces air pockets within the batter that makes final product slightly more fluffy, but still varies significantly from the souffle style.

The cooking of the pancake also gives it that beautiful brown colour, which is likely the Maillard reaction occuring as the temperature of pans would not reach the high caramelization temperatures of table sugar (glucose).

We had fun eating our pancakes with maple syrup and milk 🙂 It was a fun workshop and to see people cooking outside the library for the first time.

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Sorry that this blog post is kinda lengthy~ Hope you enjoyed reading it 🙂

Next chapter: Ice Cream & Chocolate!