The Transformation of Starch
- Daisy Lin
- 2 days ago
- 3 min read
Starch is omnipresent in our every day diet. It is the main and most commonly consumed form of carbohydrates in the human diet, taking up around 45% of our daily caloric intake. Starch can be extremely harmful when consumed in excess. Fortunately, it is able to reshape into a healthier alternative. So how do these transformations work, and how can we use them to our advantage? Let’s break it down
Starch is a complex carbohydrate that’s used as a thickening agent in cooking. Soups, sauces, and pasta commonly include some form of starch. In order to activate its role, most starches require heat: just adding the powder to liquid doesn’t hold the same effect. From here, it undergoes a process called gelatinization.
Gelatinization aims to break down the intermolecular forces in starch. It’s important to know that starch is made up of two polymers: amylose and amylopectin. Water first enters amorphous regions of the carbohydrate, which then penetrates crystalline areas of amylopectin.
Heat plays an essential part of this process by causing these areas to spread out, allowing water in. This causes swelling and an increase in the percentage of amorphous areas. Eventually, amylose chains begin to separate and diffuse out into the surrounding water, disintegrating the granule structure of starch. In simpler terms, gelatinization allows starch to engage water and dissolve, thus increasing the viscosity of the liquid.
Consuming too much gelatinized starch can happen easier than you think. Foods such as pasta, bread, and cereal are all considered to have a high starch content. Because starch is a carbohydrate, overconsumption can lead to a higher risk of obesity, an increase in blood sugar levels, and other health issues.
This problem raises the question: How can we alleviate these health risks without abandoning our favorite high-starch foods?
Luckily, gelatinized starch is capable of forming resistant starch. The main difference between resistant starch and normal starch is that resistant starch isn’t digested in the small intestine like other starches. Instead, it travels into the large intestine, where it acts as a prebiotic—feeding beneficial gut bacteria. Resistant starch poses fewer health risks than regular starch and even supports digestive health.
To form resistant starch, gelatinized starch has to undergo the process of retrogradation. Retrogradation occurs when cooked starch cools down. Short-term retrogradation occurs after a few hours of cooled storage and is irreversible, meaning it can’t reform back into gelatinized starch after being heated. Long-term retrogradation occurs after 12 hours of cooled storage and is reversible.
When starch is in storage, the previously dissolved amylose and amylopectin structures start to rearrange itself. Amylose crystallization occurs at a much faster rate than amylopectin. This means that short-term retrogradation focuses more on amylose rearranging and long term-retrogradation is dominated by amylopectin rearranging. More and more crystalline areas start to form, which causes the substance to expel some water. Although the newly-formed resistant starch is healthier for consumption, the quality of texture might go down.
Understanding the science behind what we eat is crucial to meet our nutritional needs. By using the process of retrogradation, we can consume smartly by promoting gut health.
Daisy Lin is a rising junior at Thomas Jefferson High School in Alexandria, Virginia. She volunteers at a local non-profit school and teaches a science class for elementary schoolers, helping conduct lessons and experiments. She is also interested in art.
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