Not all vegetables can be used in cold dishes. Starchy vegetables like potatoes, taro, and Chinese yams must be cooked, otherwise the starch granules will not break down, making them indigestible by the human body. It is best to eat such vegetables less often in cold dishes.
Category 1: Wild vegetables such as purslane
Wild vegetables like purslane need to be blanched to thoroughly remove dust and small insects to prevent allergic reactions.
Category 2: Cruciferous vegetables
Cruciferous vegetables such as broccoli and cauliflower are rich in nutrients. They taste better after blanching, and their abundant dietary fiber is also easier to digest.
Category 3: Mustard and mustard-green vegetables
Mustard and mustard-green vegetables like turnips contain a substance called glucosinolate. When hydrolyzed, it can produce volatile mustard oil, which promotes digestion and absorption.
Category 4: Vegetables high in oxalic acid
Vegetables high in oxalic acid, such as spinach, bamboo shoots, and water bamboo, have oxalic acid that combines with calcium in the intestines to form calcium oxalate, which is difficult to absorb and interferes with the body's calcium absorption. Therefore, they must be blanched in boiling water before being served cold to remove most of the oxalic acid. Additionally, for vegetables like lettuce and water chestnuts, it is best to peel, wash, and blanch them in boiling water before eating raw. This is more sanitary and does not affect the taste or nutritional content.
Green beans contain large amounts of saponin and hemagglutinin. If not cooked thoroughly, they can cause food poisoning. The cooking time for green beans should be long, not short, until they are fully cooked and their color changes, before they can be safely eaten. Bean sprouts should be stir-fried. Even in cold dishes, they must be cooked first.