If you're unsure whether your menudo is bad, there are a few things you can do to check. First, take a look at the color of the soup. If it's anything other than a deep red, it's probably not good anymore. Next, smell the soup - if it smells sour or off, it's time to toss it. Finally, give the soup a taste - if it's sour or rancid, you'll definitely want to discard it.