Why does lotus root turn black? Latest explanation of the causes
Lotus root is also known as mi, rong yu jie, and yu ling long. It grows underwater and is rich in nutritional value. Eating lotus root regularly can boost our immunity and also help reduce internal heat, making it one of the vegetables many people love to eat. However, in daily life people often encounter the phenomenon of lotus root turning black. After buying lotus root and not finishing it in time, you will find after leaving it for a while that it has already turned black. So what exactly causes lotus root to turn black? Today we will help you understand the causes of lotus root turning black and the solutions!
1. Causes of lotus root turning black
In fact, the reason lotus root turns black in an iron pot is related to the polyphenolic chemical substances it contains. These substances share a common property: they can combine with iron ions to form purple or blue colored complexes. One of the abundant polyphenols in lotus root, gallic acid, combines with iron ions to form a blue-black substance, which is the main component of blue-black ink. No wonder it can turn pork rib soup into ink soup.
The secret of lotus root stewed in an iron pot turning into ink has been found, but why does lotus root that has not come into contact with any iron utensil and is just placed in a vegetable basket also turn black? This is because the polyphenolic substances in lotus root mentioned above, under the action of polyphenol oxidase (PPO), are oxidized into a chemical substance called “quinone”, and these quinones then polymerize together to form melanin. In fact, cut apples turning brown and bananas in the refrigerator turning black are both due to this reason.
2. Solutions for lotus root turning black
In fact, keeping lotus root white by nature is not difficult. Blanching in boiling water at 100°C for 70 seconds can deactivate all polyphenol oxidase, thus halting the process of polyphenols turning into quinones. However, this method may only be suitable for dishes like pork ribs stewed with lotus root that require a soft and glutinous texture. If you use this method to make cold dressed lotus root slices, although they will not turn black, they will also lose their crisp texture.
Do not worry. In addition to high-temperature treatment, properly adding acidic substances can also tie the hands and feet of polyphenol oxidase. When making cold dressed lotus root slices, immediately add vinegar to the blanched lotus root slices, which can greatly avoid the catalytic effect of polyphenol oxidase and keep lotus root white in color. In fact, some ready-to-eat packaged lotus root slices have added substances such as citric acid that inhibit polyphenol oxidase activity.
For those fresh lotus roots bought and not finished within a short time, how can they be kept white? This is not difficult either. Although polyphenol oxidase has a strong catalytic effect, it requires the participation of oxygen for the phenolic substances in lotus root to oxidize into quinones, so isolating oxygen is also a method. Soaking lotus root in water can slow down the process of lotus root turning black.
There are many ways to prepare lotus root that we know of, including cold dressing, stir-frying, stewing soup, and braising, among others. Lotus root enjoys the reputation of the king of ingredients because it has many cooking methods and can also be paired with different cuisines. In fact, there are many little secrets in life that we do not know. As long as we discover them with care, we will gain something. After reading this, I believe everyone has some understanding of how to handle lotus root, right?