Tween (or polysorbate) is a non-ionic surfactant with a peculiar smell, warm and slightly bitter. It is a series of partial fatty acid esters of polyoxyethylene dehydrated sorbitan. It is widely used as an emulsifier and solubilizer for oily substances. Polysorbate is generally considered to be a non-toxic and non-irritating material. According to the assessment of WHO, the daily intake can be as high as 25 mg/kg body weight based on the total polysorbate.