Starch is a complex carbohydrate that provides a ready source of energy. It is easily broken down by alpha amylase enzymes and absorbed into the blood stream. Starch is commonly used as a thickener in foods. Common sources include corn, potato, tapioca, and wheat. In this article, I outline a few properties of starch that you might find interesting.
Starch Is Made Up of Glucose But Is Tasteless
Glucose, glucose, everywhere, but not a taste! This is because the glucose is no longer free but is bounded closely together in a large complex consisting of hundreds of glucose molecules. Therefore, the shape and size of starch is very different from glucose molecules. Glucose can bind to taste buds and send signals to the brain that we are eating something sweet. Starch cannot trigger this signal.
Starch Can Be Easily Be Digested
Starch is a complex carbohydrate similar to cellulose. However, it can be easily digested while cellulose cannot. That’s because although both are made up of glucose, the way the glucose is joined is different. In starch, glucose is connected by alpha 1, 4 and alpha 1, 6 glycosidic bonds. These bonds are recognized by enzymes in the human body and therefore can be easily cleaved to yield energy. Cellulose is made up of beta 1, 4 bonds which our enzymes cannot recognize.
Starch Can Behave Like Fiber
While starch is generally highly digestible, a small percentage may resist digestion. This type of starch is referred to as resistant starch. There are different forms. The type known as RS3 is made from cooked starch that has recrystallized. Resistant starch bypasses digestion in the small intestine and goes to the large intestine where it is fermented just like fiber. Beans are known to have a high concentration of resistant starch. This is responsible for their slow digestion compared to simple carbohydrates that produce rapid increase in blood glucose after they are eaten.
Starch is Responsible for Bread Staling
When bread becomes dry and crumbly, and loses its sensory appeal, we say it is stale. The process is due to starch retrogradation or recrystallization. In this process, starch transitions back to its more ordered structure. The best way to reduce staling is to freeze your bread.
Starch Cannot Dissolve in Water Unless Cooked
Raw or native starch is composed of granules having a very strong and stable semi-crystalline structure that cannot be easily dissolved. However when heated, the crystal breaks down to form a more amorphous structure that is capable of water absorption and binding. This property is great for thickening food products such as soups and sauces.
Starch Can Make You Walk On Water
Have you ever seen one of those funny videos where someone adds starch to water in a tub or swimming pool and then walks across it. It’s always amazing to watch. A ratio of 2 cups of cornstarch to one cup of water can do the trick. The mixture turns into a non-Newtonian fluid called oobleck which gets harder whenever it is poked. Therefore, a person walking or running on oobleck will never sink. They can only sink if they stand still.
Starch Turns Bluish Black When Iodine Is Added
A quick test for starch is to add iodine. It quickly turns the starch bluish black. This happens because iodine slips into the center of the helical amylose crystal found in starch.
Starch has many interesting functional properties due to its unique physical and chemical structure. These functional properties are useful for various food processing applications.