After few day of plastick bag packing of Tomato sauce increase the size of it and produce gas in plastic bag

I am one small manufacturer of tomato sauce and dates sauce . And my question is regarding preservative i.e we make tomato sauce and paking it in plastic bag after few day this paket size increasing and produce gas in plastic bag ,so I want to know about proper method of manufacturing . Our preservatives are sodium benzoate, acitic acid and suger.