Different ingredients and different uses.

1. Lactose and white sugar are different in composition. Lactose is a disaccharide composed of glucose and galactose and is found primarily in dairy products. White sugar is a simple sugar, glucose, which is pure sugar extracted from sugar cane or beets. Therefore, the chemical structures and compositions of lactose and white sugar are different.

2. Lactose and white sugar also have different uses. Lactose is mainly used in the processing and production of dairy products, such as milk, milk powder, dairy pastries, etc. Because lactose requires the enzyme lactase to digest lactose in the human body, some people may be lactose intolerant. White sugar is a common edible sugar that is widely used in food processing such as cooking, baking, making desserts and beverages. White sugar has a high sweetness and is easy to dissolve, so it is widely used in various fields.