When people use the microwave to heat Mantou, steamed buns and other flour products, have you ever had this problem: Mantou is put into the microwave to heat, but it is still soft when it is just taken out, and it will become hard, dry and even hard like "stone" after a dozen seconds.
People generally think it's simply 'dried', but the real reason is not only dehydration, but also irreversible changes in starch structure. The long heating time is a very important reason, which is also the biggest difference between microwave heating of noodles and steaming pot heating.
1、 Microwave ovens use "rapid vibration heating of water molecules", and their dehydration speed far exceeds that of steamers
The steamer is heated in a humid and hot environment, and the environment is full of steam. Mantou will only heat up, almost without losing water, so it is soft and glutinous.
Microwave ovens generate heat through high-speed friction of water molecules excited by high-frequency electromagnetic fields. The free water and combined water in Mantou will boil, evaporate and run out of the pasta in a short time.
The ordinary heating is slow heat transfer, and the microwave generates heat directly from the internal water molecules. The water loss rate is extremely fast, and the rapid water loss on the surface is the first reason for the drying of Mantou.
Here we should pay attention to: if the heating time is properly controlled, the water will not be lost in large quantities, and Mantou will not be easy to dry and hard; Once the heating time is too long, a large amount of water will continue to evaporate, and the problem of dryness and hardness will immediately worsen.
2、 Core Key: Starch 'Rapid Dehydration and Hardening'
The essence of Mantou soft waxy is that starch absorbs water and gelatinizes to form soft gel structure.
The Mantou that is cooled normally hardens, and the starch slowly recovers; But the hardening after microwave heating is rapid structural hardening.
After microwave takes away a large amount of water instantaneously, the starch gel structure loses water support, collapses rapidly, shrinks, and solidifies compactly, which is called starch vitrification in the industry.
Simple colloquialism: ordinary cold Mantou hardens=slowly recovers; Microwave oven Mantou hardens=starch directly hardens after dehydration. This hardening is mostly irreversible, and it tastes dry, hard, and inelastic when eaten. The longer the heating time, the more severe the dehydration, and the more obvious the phenomenon of starch hardening.
How to heat it to make it soft and sticky?
When heating, add some water to the Mantou plate/cover it tightly to lock the water and simulate the humid and hot environment; At the same time, strictly control the heating time and avoid prolonged high heat heating. By using a dual combination, the soft texture can be maintained after heating.
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