Why have these outbreaks only happened in the past 15 years?
Some of these processing plants are quite dated, and that may be part of the problem. They just haven't been maintained. Thirty years ago when they were built, they didn't have leaks like that.
Is there any way to destroy the bacteria once it's in there?
Not by current procedures.
Theoretically, you could irradiate it. It's not an approved process. And because it’s a high-fat product, you'd get a lot of off odors because of lipid oxidation. I'm not sure radiation would be good approach.
We have done thermal inactivation studies on trying to kill salmonella in peanut butter. But even when you get up to 190 degrees Fahrenheit (90 degrees Celsius), it takes many minutes and might affect the integrity of the product. Heating may not be an easy fix.
So, how can you keep salmonella out of peanut butter in the future?
The key is to have a rigid system in place that does not allow contamination by water or other vectors after the roasting process. Water in a peanut butter processing plant is like putting gasoline on a fire. It will not only spread the salmonella, but the salmonella will grow when water is present. Salmonella is not likely to grow in a dry environment.