Why can fried potatoes be crispy outside and soft inside? Why do fried sweet potatoes make the color more golden? Why is the smell of fried food so different from other foods? In fact, all these can be explained by science. This issue of fried cooking science will show you the chemical changes of three kinds of starch during frying!
Reaction to make fried food appear golden yellow
The creator of the striking golden coat of fried food that gives food a beautiful coat is Mena reaction, which is a chemical reaction of "reducing sugar and amino acid" at high temperature. This reaction requires three key steps:
Remarks: Reducing sugar refers to the sugar that can produce aldehyde group and carbonyl group in alkaline solution, such as monosaccharide, lactose and maltose. Both starch and refined sugar contain this reducing sugar.
Step 1. Dehydration and rearrangement of reducing sugar and amino acids;
N- glycosylamine is formed by dehydration of carbonyl group with amino group and reducing sugar, and N- glycosylamine is rearranged by continuous heating to form fructosamine, also known as Amadori rearrangement product.
Step two. Further degradation of fructosamine at high temperature;
After continuous heating, fructosamine continued to react at high temperature. After several reactions, such as dehydration, crushing, enolization or Strake degradation, a variety of products with or without fragrance are produced.
Step three. Amine group degenerates again:
At the end of the reaction, the amino group returns again, and after condensation, dehydrogenation, cracking, cyclization and other reactions with various products in step 2, a brown nitrogen-containing polymer, also known as melanoid, is formed, which is the protagonist of the golden coat of fried food.
Because amino acids participate in Mena reaction, the reaction speed and quantity are faster than Cramelisation, and the high temperature of frying, starch of frying powder and amino acids of ingredients perfectly meet the necessary materials for Mena reaction. With the passage of time, the food was dressed in a golden coat from head to toe, and the clothes were finished, which became delicious on the table.
A chemical reaction that makes fried food smell attractive.
Besides the golden coat, fried food is more attractive. Every time I pass by the salty crispy chicken stall, I can't help but be attracted by the fragrance alone. How did this mouth-watering aroma come from? Volatiles produced during frying are the main characters of attractive fragrance, and the sources of these volatiles can be divided into two types:
1. Fried oil
High temperature decomposes oil into free fatty acids and produces many peroxides. These unstable peroxides will make decomposition more active and produce many volatiles, such as ketones, aldehydes and esters. 1998 The volatiles produced when frying oil is heated are analyzed, and it is found that there are nearly 100 compounds from beginning to end. Among them, aldehydes are the main components that provide attractive aroma, and other compounds will be produced, volatilized and then disappeared during frying, which is a process of constant change and emission.
From food
There are many sources of food, such as fried pork chops, which are also divided into stir-fried and fried with powder. Different preparation methods will also affect the aroma!
Take fried pork chops as an example. When frying, pork chops are in direct contact with oil, and the oil contained in pork chops will be mixed with oil. Lard has more saturated fat, while salad oil has both saturated fat and unsaturated fat. Different oils will make fried oil decompose faster. When meat is heated, it will produce sulfur-containing compounds and various heterocyclic compounds, which will be mixed with the compounds produced by oil, so it will produce a completely different flavor from fried oil.
In addition, when starch coated with flour is fried, it will produce ketone groups, aldehyde groups and other compounds with simpler structures. There are fewer kinds, and the smell is very different from the smell of meat, so this difference will let you know that this is fried pork chops instead of French fries!
The gelatinization reaction makes fried food thick and delicious.
When frying, the crispy layer formed on the surface of fried food can preserve the water in the food, but heating will make the water evaporate continuously, and the evaporated gas will open the gap between starch particles, and water will surround the starch particles from the gap, so that the linear and amylopectin in the particles will form polymers and dissolve in water, and the starch particles will be completely destroyed by continuous heating, forming a translucent colloidal solution. This process is called gelatinization reaction.
Food gelatinizes from the moment it comes into contact with hot oil. It was found that the water content required for gelatinization should be at least 20%, so the gelatinization reaction on the surface of fried food started and ended quickly. Only the food center is protected by the outer layer, so the water will not evaporate to keep the food gelatinized. Like fried sweet potatoes, the skin remains crisp and the center still retains enough water, which can make the starch in the center gelatinize continuously and provide a dense taste. This is the delicious secret of fried food that is crisp outside and soft inside.
The golden coat that we see with our eyes, the attractive aroma that our nose smells, the strong smell of biting, and the sparks that food and oil inspire, let us enjoy the beautiful feeling brought by fried food from three different senses. Although high calorie and fat have adverse effects on our health, if we make good use of oil, choose fresh food, use appropriate preparation methods, eat more vegetables during meals, keep enough exercise and eat fried food, we can easily reduce your burden!
Good food class authorized to reprint the original source of delicious science of fried food, and once analyzed three changes of fried starch.
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