When it comes to plant sausage, there are a few things you can look for to determine whether or not it has gone bad. The first is the color. If the sausage is brown or grey, it is likely past its prime. Another indicator is the smell - if the sausage smells sour or off, it's best to discard it. Finally, take a close look at the texture. If the sausage is slimy or has developed mold, it should be thrown away.