Do we need to wash the raisins before eating？

Given the production process， fresh grapes must first be treated with alkali： immerse the grapes for 1-5 seconds in 1.5%～2% sodium hydroxide solution （grapes with thin skin can be immersed in 0.5% sodium carbonate or the mixture of sodium carbonate and sodium hydroxide for 3-6 seconds）. After the alkali treatment， rinse the grape immediately with water （there requires extra 3 to 5 hours for sulphuration to dry white grapes）.

Then put the grapes into a container and expose them in the sun for 10 days or so. When a part of the surface is dry， flip the grapes so that the inner facing outwards. Put away the container and dry the grapes directly for another week once the most of the grapes are dried. The total time for drying is 25 days if it is sunny. Then stack the raisins together for a week to soften them and the moisture will be distributed evenly.

This method is done outdoors in the sun， and there will inevitably have dust， so from the point of food safety， it is better to eat raisins after washing.

（Answerer： Jianping WU National First-level public nutritionist）

（Source：the WeChat Official Account of Knowledge is Power）endprint