Why do you add bran when boiling bamboo shoots?

I don't think I usually boil bamboo shoots at home, but I think I've heard of boiling with rice bran.

Bamboo shoots are plants that grow rapidly immediately after germination, and their metabolism is also active, so if you dig them up and leave them alone, the ingredients will change in increments of one minute.

Freshly dug bamboo shoots are soft and tasty, so you can eat them without boiling them, but after a while they become hard and have a harsh taste.
In particular, oxalic acid, which is the main component of harshness, increases by 2-3 times after 24 hours of standing.
When the bamboo shoots are boiled, adding 20% ​​to 30% of the amount of rice bran to the amount of water dissolves more than 10 times more oxalic acid than when the bamboo shoots are boiled in water alone, and the amount of oxalic acid remaining in the bamboo shoots is reduced by about half. It is also said that the starch particles of the rice bran cover the surface of the bamboo shoots, preventing oxidation and making them white when boiled.
It is said that boiling bamboo shoots with the skin on will make them softer, but this is thought to be due to the reducing sulfite contained in the skin, which prevents oxidation and softens the fibers.

In addition, the enzymes in the bran soften the tissue of the bamboo shoots, and the starch in the bran coats the bamboo shoots to protect the ingredients inside.