Red bean soup called patjuk (팥죽) is commonly eaten during the winter season. On Dongjinal, a Korean traditional holiday which falls on December 22, Korean people eat Donji patjuk.
In old Korean tradition, patjuk is believed to have a mysterious power to drive evil spirits away. According to Korean traditional folk beliefs, the color “red” is a symbolic color of positive energy which can defeat negative energy. Cooking and eating patjuk is a ritual to prevent bad luck, epidemic disease, and comes from evil spirits. Before eating the dish, Korean people used to serve it their own house shrine, they scattered it all around the house like in the kitchen, storage house, gate, yard and so on.
Patjuk embodies a custom of conserving food. Koreans usually eat rice and side dishes. However, in the wintertime when Korean families had shortage of grains, patjuk became a complete meal itself. It could be made of simple ingredients. For example, red beans, water, small grains of rice and also it requires no need extra side dishes. Thus, when people prepare some events in winter, patjuk is an economical food for conserving grain (Source)