I found a debate on the Internet. Here's one comment, it might help us.
I have been making soap approximately 15 years. I use veggies in my soap all the time and I make it using the CP method. THIS ADVICE IS NOT TRUE FOR MELT AND POUR SOAP.
It is science. Soap is an alkaline, like salt, which was used to preserve beef before we had proper refigeration methods. If you puree your veggies to a water consistency in the proper percentage it will react chemically with the soap making process and will combine in the final soap thus being preserved by the soap. You are more likely to find bacterial growth in your lotion products which are binding oils and water. Ive seen lotion grow mold just through using the wrong preservative.
Furthermore if by your theory that fruits and veggies add to bacterial growth, what do you think would happen adding goatsmilk or coconut milk? Or the fact that you are adding water to oils?
Use common sense. make sure you are adding it at the right percentage and that it is pureed into liquid form. Yes it is SCIENCE. Even if you dont send it off to a lab. Soap making is science. Btw have you looked at studies involving many commercial preservatives? Scary!