How much sodium benzoate to put in you liter of ketchup?

The typical usage rate for sodium benzoate as a preservative in food products is around 0.1% to 0.2% of the total weight. For one liter of ketchup, which weighs approximately 1,000 grams, you would use about 1 to 2 grams of sodium benzoate. Always ensure to follow food safety guidelines and regulations specific to your region when using preservatives.