1. The tomato sauce may not have been sterilized or autoclaved when it was homemade, so there may have been bacterial growth, resulting in red foam spraying out.

2. Improper storage of homemade tomato sauce, such as high temperature or unhygienic storage environment, may also lead to the growth of bacteria, causing red foam spraying.

It is recommended not to consume tomato sauce that has spoiled to avoid food poisoning. If you need to preserve tomato sauce, you can keep it in an airtight container in the refrigerator to extend the shelf life.