People often like to eat hot sweet potatoes to keep them warm in winter. However, some people might be concerned that purple sweet potatoes may have been artificially coloured, as bluish-purple colored liquid may seep out when they are washed or cooked.

Actually, the above-mentioned observation is a natural phenomenon. Purple sweet potatoes are known to contain a natural water-soluble pigment - anthocyanin. Anthocyanin is a pigment commonly found in some fruits and vegetables like grapes, red cabbage, and berries. Generally speaking, eating fruits and vegetables containing anthocyanin is not harmful.

When purchasing fruits and vegetables, please take note of the following points:

• Buy fruits and vegetables from reliable and reputable sources, and do not patronise illegal hawkers
• Try to avoid buying extremely low-priced fruits and vegetables with abnormally bright colours
• If the colour of vegetables looks suspicious upon cooking, it is advised not to eat them