Once opened, tomato sauce can be kept in the refrigerator between 5 and 7 days. After this time, the sauce may develop mold, which contains harmful toxins.
Tomato sauces or tomato-based sauces for pasta have a long shelf life when unopened. They can last for up to 1 year unopened in the pantry. Most tomato sauces do not have preservatives, which means they should be consumed quickly.
Do not actually wait to see mold on the sauce before tossing it, since it may be present in the food days before it becomes visible. Other signs that tomato sauce may be spoiled include getting thicker, and darkening from red to a brown hue. The temperature of the refrigerator, as well as any kind of cross contamination and exposure to bacteria, can also affect the shelf life of tomato sauce.
Besides mold, other common spoilage organisms include lactic acid, bacteria and yeast. In general, the longer the jar has been opened without being refrigerated, the higher the chances it will spoil sooner. Always refrigerate the sauce in a tightly sealed jar or container. To keep the tomato sauce for a longer time, consider placing it in a sealed container in the freezer.