Everyone who fry rice may face a common problem which is that fried rice sticks to the pan.
Regardless of cast iron pan, carbon steel pan, stainless steel pan, or Teflon non stick pan, all these are facing the fried rice sticking problem.
So actually what is the science behind the food sticking to the pan?
And probably what we have done may cause the food sticking to the pan?
Here I am going to discuss why fried rice sticks to the pan or wok (basically both pan and wok are about the same, just different in shape, pan is flat bottom and wok is round bottom) and hope it helps you.
Table of Contents
Why does fried rice stick to pan (or wok).
Fried rice sticks to the pan because food molecules (protein & carbohydrate) form strong chemical bonds with the pan (metal atom like iron), and enhanced by the tiny pores, uneven surface on the pan surface. The fried rice sticks to the pan, probably the pan is not seasoned, not properly seasoned, or seasoning weakens during the washing process. Lack of oil and slow stirring rate during cooking are also the factors of fried rice sticking. For a Teflon pan, probably the non-stick coating layer is damaged.
Science behind food sticking pan.
Fried rice sticks to the pan because food is forming a chemical bond with the pan.
Food refers to carbohydrates and protein.
Pan material is metal, it could be cast iron, or stainless steel.
When heat is applied, van der Waals forces (relatively weak) or covalent bonds forming between food and pan.
The surface of the pan looks flat and smooth.
But if you look at the surface of the pan through a microscope to magnify the view, you will discover there are a lot of valleys, caves, cracks, and tiny pores on the surface.
So the pan surface is not smooth and not flat.
Because of the rough surface the food easily sticks to a heated pan.
Especially the protein rich food like egg, protein molecules (acid amino) can form chemical complexes with metal like iron.
The pan is not seasoned or not properly seasoned (for cast iron, carbon steel, and stainless steel pan).
A layer of barrier needs to be created between food (fried rice) and the pan surface.
Seasoning process is to bake a layer of carbonized oil on top of the pan surface for cast iron, carbon steel, and stainless steel pans.
As the layer is built up, the carbonized oil fills up the pores, small cracks , valleys of the pan surface and forms a smooth, even, and non-stick surface.
If your pan has the problem of fried rice sticking to the pan, most probably the pan is not seasoned or not seasoned properly.
For the new pan that you just bought, you may find an instruction that is attached together with the new pan on how to clean (the new pan contains industry oil) and season the pan.
The pan seasoning weakens during washing.
For cast iron, carbon steel, and stainless steel pan, washing the pan with water could weaken the seasoning layer, even before that the pan is well seasoned.
Adding soap could easily wash away the seasoning.
And using something that is too abrasive (steel wool, metal scrubber, and harsh detergent) also could remove the seasoning layer as well.
Cast iron and carbon steel pan have better resistance of seasoning layer wash away by water compared to stainless steel pan.
This is because cast iron and carbon steel pan have bigger size pores compared to stainless steel pan’s pores.
With larger pore size, the oil is able to penetrate deeper into the pan, this makes the seasoning of cast iron & carbon steel pan can last longer and more resilient to be washed away than stainless steel pan.
To avoid the seasoning layer washed away, some people choose not to wash the pan with soap after using it for cooking, just wash with water only.
For cast iron & carbon steel pan, regularly using them for cooking could strengthen the seasoning layer as you are adding oil & fat when cooking.
Lack of oil when frying rice.
When frying rice, the rice and food ingredients will absorb the oil.
When the pan becomes dry, the fried rice will start to stick on the pan surface and get burnt.
Some amount of oil needed to stay in the pan for frying rice without sticking and burning.
Fried rice stays on the pan surface without stirring for too long.
There might be a hot spot at the pan surface.
The hot spot might be created due to the material of the pan and the heat source.
If rice or food stay at the pan’s hot spot for too long without moving, there is a high chance the fried rice may stick at that spot and get burnt.
High stirring rate also ensures the fried rice is uniformly cooked.
When you enter the Cantonese restaurant, you may see the chef toss-fry the fried rice at high speed.
Non-stick coating damaged (Teflon)
If you are using a non-stick Teflon pan to fry rice and experiencing fried rice sticking problems, most probably the Teflon non-stick coating layer is damaged.
The non-stick layer might be damaged for a few factors.
The non-stick coating layer is scratched by metal spatula, or by abrasive steel wool scrubber when washing, or anything which is hard and sharp enough to damage the coating layer.
Another factor might be the Teflon layer is damaged by high heat.
Generally, heat that is applied to a Teflon pan cannot exceed 260 °C (500 °F).
High heat will break down Teflon molecules and release toxic gas into air.
You can see discoloration at the Teflon pan which is already damaged by high heat.
Preheating an empty Teflon pan could heat up the pan to a high temperature and cause coating layer damage.
In summary, when you notice the fried rice is sticking to the pan, check the seasoning of the pan as it may be washed away by water and soap, or corroded by an abrasive object. It is time to season the pan again.
If fried rice sticks to a Teflon non-stick pan, it might be that the nonstick coating layer is damaged and no longer stops the food molecules bonding with metal atoms.
When frying rice, increase the stirring rate to avoid the rice and ingredients sitting in the same location for too long and add some oil if it is drying in the pan.