I made pizza today. The last time I did this I had some leftover tomato sauce; when I opened that it went POP and smoke came out of the jar. Tasted really bad, too, so I threw it away and opened a new jar.
I keep having to do this. I close the jar tight and put it directly in the refrigerator, but it still goes bad.
What can I do to prevent this? Is there some sort of preservative I could add to the remaining sauce to keep it from spoiling?