My daughter eats oatmeal for breakfast, just boiled oats with some sugar and milk. She likes it, but she eats slowly. Like any 13-year-old girl, she also sits down to eat breakfast a few minutes before the school bus arrives. Inevitably, there are leftovers. “I promise I’ll have it in the evening,” she said recently before rushing out the door. When evening came, we took the remaining oatmeal out of the fridge, but its consistency had changed, looking watery. Meanwhile, the second portion of extra, untouched oatmeal that I had also saved from the pot that morning was not only not thick, it was slightly congealed. This seemed rather strange.
I can’t be the only one who noticed this, right? So I started searching for information about foods that soften after cooking and found several questions posted on various cooking websites over the years. In almost all cases, they used starchy or starch-heavy recipes:
- Why is leftover chowder watery?
- Why do all my thick sauces and soups turn into a thin liquid when I eat them?
- Why does my soup get thin halfway through serving?
People often responded with more questions: What type of starch did you use to thicken the dish? How much did you add? How long did you cook it? The original poster’s answers tended to indicate that these lines of inquiry were dead ends.
So, why were these foods so thin? No one seemed to know for sure, but every now and then someone in the discussion would make a suggestion that made everyone uncomfortable: Have you double dipped into food?
It’s a question that comes with the inevitable “eww!” Factor – Double dipping is like backwashing, and most of us cringe at the idea of bad mouth germs mixing with whatever we haven’t yet consumed. If we can pause our vomiting reflex for just one second, there are a lot of interesting things about this suggestion, because what it hints at reveals more than just the answer to the puzzle of food dilution; it’s a great example of the important digestive powers of saliva.
Without saliva, eating and digestion would be much more difficult and less effective. Mucus in saliva, for example, is necessary for swallowing. When we chew, the mucus and water in saliva turn dry or crumbly food into a soft, sticky mass called a bolus, making it easier to swallow. This helps prevent choking and protects the esophagus from damage caused by rough food particles.
But mucus is not the main point here. Saliva is mostly water, about 99%. The remaining 1% is a mixture of mucus, proteins and electrolytes. Among the proteins there are enzymes that help break down food into smaller pieces, making it easier for the body to digest. The most abundant enzyme in saliva is salivary amylase, and this is the critical enzyme to consider in this conundrum of diluting and double-dipping foods.
Salivary amylase: I have one job to do
The task of salivary amylase is to break the α-1,4 glycosidic bonds in starch molecules to form smaller units such as maltose and dextrin. Not surprisingly, it works inside the mouth. This is where the saliva is located. What’s surprising is that it continues to work outside The mouth, too, which may cause potential shock and horror to oatmeal eaters, soup drinkers, and party guests crowding around dipping bowls everywhere.
But this shouldn’t surprise you, because you’ve seen amylase enzymes operating outside their intended environment before. When you hydrate flour to make dough, the enzyme amylase in the flour begins breaking down the starches into smaller units for the yeast to feed on, starting the fermentation process and producing the gases that cause bread to rise. Even traditional alcoholic beverages, such as chicha and masato beer, use saliva to start the fermentation process, breaking the starches into smaller pieces that can then be fermented by yeasts. Enzymes takes the motto “You only have one job to do” very seriously. Like robots programmed in an infinite loop, they continue to do their work until they finally become inactive, whether denatured by changes in pH or temperature, or stopped by dehydration.
Salivary amylase test on starchy foods
Now that we know that amylase can continue to function outside the body, the question is: What types of foods might it affect, and under what conditions? To test this, I needed a few starch-dense dishes. Here are the ones I tested:
In all these cases, the dishes were partially or completely thickened with starch molecules, a simple and inexpensive way to make foods less runny. It works by heating a liquid containing starch; Once the temperature exceeds 140°F (60°C), the starch molecules begin to break down and absorb water in a process called gelatinization. The initially cloudy mixture turns into a clear gel, trapping water molecules between the starches.
I compared one group of untouched starchy foods (as a control) with another group in which I licked a spoon and swirled it around the foods. She repeated the licking and rotating process three times. After waiting 15 minutes, I checked the results.
Why 15 minutes? Researchers estimate that salivary amylase remains active in the body for about 15 minutes before the food we chew and swallow fully mixes with gastric juice, where the acidic environment denatures the enzymes. This time also roughly matches how long it takes to finish a meal. Therefore, whether inside or outside the body, we should see the effects within this time frame. All dishes were kept at room temperature, as enzymes work best at body temperature of 90-98°F (32-37°C).
If the enzymes did their job, the smaller cleaved molecules would lack the thickening power of the longer starch molecules that each dish begins with. So, if my hypothesis is correct, the resulting foods should be thinner compared to the control version.
results
Within 5 minutes, I started to see some dilution in the mushroom and potato soup. After 15 minutes, the results were very significant for both the soup and the oatmeal. There was obvious thinning and it was easy to visually differentiate the control from the amylase control. Salivary amylase had a clear effect on the texture of these three foods in a short period of time.
However, the cheese sauce and mac and cheese showed very little change. Why did the hypothesis fail for thick dishes? Most likely, it’s because thicker dishes rely in part on the proteins in the cheese to thicken them. Since saliva does not contain enzymes that break down proteins, this may have limited the effect. Additionally, the increased viscosity of cheese sauce can slow down enzymes, reducing their ability to break down as many starch molecules as possible in the given time frame.
Does this mean that one should never double dive?
Enzymes work and have an effect. But if you are cooking for your family and check the salt level 18 times while cooking, you don’t need 18 spoons. Enzymes are incredibly efficient at what they do, but they are easy to inactivate. You do this on a daily basis. For example, when you apply lemon juice to apples and avocados, you inhibit the enzyme polyphenol oxidase, which prevents browning. Likewise, blanching vegetables before freezing uses high heat to quickly deactivate enzymes. Refrigerating foods also slows enzyme activity.
So, when feeding your family, don’t worry about licking the tasting spoon. Enzymes need a combination of moderate pH and temperature requirements to function optimally. The farther away from their ideal zone they are, the less they will perform. For example, placing a spoon in boiling porridge renders it completely inactive. Likewise, tomatoes or other acidic soups and soups also denature the enzymes.
But if you find a runny soup, porridge, or thick sauce or dip in the office refrigerator or at a holiday party, you might want to stay away from it… because the enzymes in someone’s spit have been hard at work!