How to take chewing gum away from my child?

Prevention. I don't think it is healthy for kids to chew gum. Therefore i would not encourage them using gum in the first place.
Set limits! Set your rules and limits for chewing gum for your child. You may provide opportunities to allow gum chewing in clearly defined guidelines/parameters. Offer an alternative choice when it comes to this consumption. Create self consciousness/inner authority re: choices/decisions made re: gum chewing.