How to keep the lotus root slices white without changing color

We all know that cold lotus root slices are a common home-cooked dish. Many people make cold lotus root slices at home, especially in summer. When many people make cold lotus root slices, they will find that the lotus root slices turn black, which is a normal phenomenon. So how can cold lotus root slices not turn black? Let's take a closer look!

Why does the cold lotus root slices turn black?

To make the lotus root slices white and not black, we must first understand the reasons why the lotus root slices turn black. Only by understanding the specific reasons for the blackening of the lotus root slices can we find a solution. There are two main reasons why the lotus root slices turn black: one is that the polyphenols in the lotus root slices undergo oxidation reactions to produce black substances. The other is that the polyphenols in the lotus root slices react with iron ions to form complexes and change color.

1. Lotus root slices contain a large amount of polyphenols, and these polyphenols can easily produce quinones under the action of their own polyphenol oxidase. When quinones aggregate, they appear black.

2. The polyphenols in the lotus root slices react with iron ions to form a complex that is blue or black in color.

According to the above two reasons, as long as the polyphenols can be prevented from reacting, the color of the lotus root slices can be kept white and not black. To prevent the lotus root slices from undergoing oxidation and complexation reactions, the conditions for the reactions must be changed.

How to prevent the cold lotus root slices from turning black

The two prerequisites for the oxidation reaction of polyphenols are oxygen and polyphenol oxidase. To prevent the oxidation of polyphenols, these two prerequisites must be changed. The specific approach is:

1. Isolate oxygen

After the lotus root slices are cut, quickly soak them in cold boiled water to isolate the oxygen in the air, delay the oxidation reaction of the lotus root slices, and delay the discoloration of the lotus root slices. Note that the lotus root slices should not be exposed to the air for a long time after being cut. They should be put into cold boiled water as soon as possible to avoid oxidation and discoloration. (Tips: Be sure to put them into cold boiled water, not directly into cold water. Because the air content in the water is less after the cold boiled water is heated.)

After the lotus root slices are cut, quickly put them in vacuum packaging to isolate the air, which can keep the lotus root slices white and not change color.

2. Inactivate polyphenol oxidase

There are two ways to inactivate polyphenol oxidase: one is heating, and the other is changing the pH value of the reaction environment.

The best way to inactivate the polyphenol oxidase in lotus root slices is to heat them. Generally, polyphenol oxidase will lose its activity at around 60 degrees. Blanch the lotus root slices in boiling water. The heating time should not be too long, generally about one minute. Otherwise, the lotus root slices will become soft and not crisp. The surface of the lotus root slices will be very sticky after blanching, so quickly rinse them in cold water.

Changing the pH of the reaction environment:

The specific method is to add an appropriate amount of white vinegar or citric acid to the lotus root slices, which can effectively inhibit the activity of polyphenol oxidase, thereby avoiding the rapid oxidation reaction of polyphenols and preventing the lotus root slices from turning black.

Specific methods to prevent polyphenols from undergoing complexation reactions:

Try to avoid contact between lotus root and iron containers. Use a stainless steel knife when cutting lotus root slices, and try not to use an iron knife. Never use an iron pot when blanching lotus root slices, a casserole is best. Do not place the cut lotus root slices in an iron basin, it is best to place them in a plastic basin or a stainless steel basin.

[Summary of the key points to prevent lotus root slices from turning black]:

To prevent the lotus root slices from turning black, it is necessary to prevent the polyphenols in the lotus root slices from oxidizing or undergoing complexing reactions. Only when all links are controlled well can the lotus root slices be prevented from turning black. First of all, a stainless steel knife should be used to cut the lotus root slices, and a stainless steel basin or a plastic basin should be used to hold the lotus root slices. After the lotus root is cut, it should be blanched quickly to avoid being exposed to the air for a long time. When blanching the lotus root slices, do not use an iron pot, it is best to use a casserole. The lotus root slices should be blanched over high heat for one minute, and then quickly soaked in cold boiled water. And add a little white vinegar or citric acid to the water. As long as you pay attention to these points, the lotus root slices will be white and will not change color.

How to keep lotus root slices white

Since lotus root slices are easily oxidized when exposed to air after being cut, the only way is to reduce the chance of lotus root slices coming into contact with air. This can be done in the following ways:

1. Cut and mix immediately

Generally speaking, the cut lotus root slices will not turn black in a short period of time. Only if they are cut for too long will they gradually turn black. Therefore, when making cold lotus root slices, you must cut and mix them immediately. Do not cut the lotus root slices too far in advance.

2. Soaking method

The second method is to isolate the lotus root slices from contact with air, which is to use the soaking method. There are many ways to soak them. You can add a small amount of salt to the water, or you can add a small amount of vinegar to soak them, or you can soak them directly in water. These methods can prevent the lotus root slices from turning black.

3. Blanching

After peeling and slicing the lotus root, blanch it in boiling water for 2 minutes (the specific time depends on the thickness of the lotus root slices), then take it out and quickly soak it in ice water. This will not only prevent the lotus root slices from turning black, but also make them taste crisper.