Carbs and browning

What do we call small carbohydrates?

Monosaccharides or sugars

What are two examples of monosaccharides?

Glucose & fructose (or galactose)

What is an example of a disaccharide?

Sucrose (or lactose or maltose)

What is the difference between the structure of a monosaccharide and a disaccharide?

Monosaccharides are single sugar molecules, while disaccharides are larger molecules, each made of two monosaccharides that are covalently bonded together.

What are three properties of sugars that make them useful in the kitchen?

- Sugars dissolve very well in water. (Water can dissolve twice its weight in sugar!)
- Sugars activate our sweet receptors.
- Their crystals are extremely hard.

What are complex carbohydrates/polysaccharides made of?

Monosaccharides covalently bonded together in long polymer chains

What are some examples of polysaccharides used in cooking? Name at least 3.

Starch, agar agar, and pectin

What are the three properties of complex carbohydrates/polysaccharides that make them useful in the kitchen?

- Polysaccharides larger than 2 or 3 units are too large to activate our sweet receptors.
- Their solubility in water varies.
- They are used as thickeners.

What is enzymatic browning?

- Starts from a compound call Phenols found in certain veggies
- This reaction occurs when the fruit/vegetable is cut, bruised, or otherwise damaged and the interior flesh is exposed to oxygen. This gives the surface of the bruised or cut fruits and vegetables a dark brown color. It is generally considered undesirable.

What role does the enzyme polyphenol oxidase play in enzymatic browning?

It converts pleasant smelling phenol molecules into bitter tasting melanin, which acts as a barrier to prevent further rotting and causes the brown color.

Explain how the size of a cut potato influences the rate at which it enzymatically browns.

Smaller pieces of potato have more surface area that exposes more flesh to the oxygen in the air. As a result, there are more polyphenol oxidase reactions that cause more browning.

Enzymes are proteins, which means they can become denatured (lose their shape and, therefore, lose their function). What are the two factors that can denature enzymes?

Heat and changes in pH

What are some ways that you could slow the rate of enzymatic browning of a cut apple?

Mix it with an acid like lemon juice to change the pH or wrap the fruit very tightly/vacuum seal it to reduce contact with oxygen.

If non-enzymatic browning reactions do not involve enzymes, what is required for browning to occur?

The presence of certain substances such as sugar and/or amino acids and heat.

In non-enzymatic browning, what results in “burnt” food?

Removing hydrogen and oxygen, leaving behind more and more carbon.

What are three types of non-enzymatic browning reactions.

Caramelization, dextrinization, and maillard browning

caramelization

Molecules involved: sugars - monosaccharides or disaccharides

dextrinization

Molecules involved: polysaccharides (not sugars like monosaccharides or disaccharides!)

maillard browning

Molecules involved: sugars and amino acids (from proteins)

How are thickening and gelation similar?

Both increase a mixture’s viscosity by adding large polymers to a mixture of smaller particles

What makes thickening and gelation different?

Thickeners: increase a liquid’s viscosity and the mixture retains its ability to flow and remains a liquid

Gelation: gelation’s polymers create a matrix of large particles that trap and prevent the smaller molecules from moving, forming a solid.

What types of macromolecules are used to thicken or create gels?

Polysaccharides, fats, and protein (gelatin)

What are some advantages and/or disadvantages to each type of macromolecular thickener?

Advantages: lots of polysaccharides to choose from and its vegan

Disadvantages: can change a flavor and/or texture of the food and not necessarily vegetarian/ vegan, and some can’t be used to thicken/gel foods that are room temperature or warmer because they turn liquid, like gelatin