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Nut butters and spreads
All Containers›Shop by use case›Nut butters and spreads›The kill step›Dry is not safeShop all nut butters and spreads →
The kill step

Dry is not safe

By Dwight Davis, Founder

Updated

On this page6
This is the page the whole property rests on, and it inverts the lesson from every other craft here. Low moisture stops things growing; it does not stop them being there.

The inversion, stated plainly

A syrup is safe because its water activity is too low for anything to grow. A nut butter has a water activity just as low and is not safe on that basis. The difference is that a syrup is also hot filled, and a nut butter typically is not, so nothing in the jar has ever killed anything.

Salmonella survives in it for a long time

It does not multiply, which is the fact people reach for, and it persists. In a dry high-fat matrix it can remain viable for months, so a contamination event upstream reaches the consumer intact however long the jar has been on a shelf. Time is not a control here.

And the dryness makes it harder to kill

This is the part that surprises people. Salmonella becomes more heat resistant as water activity falls. Published work puts a five-log reduction at 140 degrees F at under five minutes in a food at a water activity of 0.99, and around fifty minutes in one at 0.85. The fat adds to that. A heat treatment that would be comfortably sufficient in a wet food is nowhere near sufficient here.

It has happened at scale

The multistate outbreak associated with peanut butter and peanut butter-containing products in 2008 and 2009 is the reference case, and it is why this product class attracts the attention it does from regulators and from wholesale buyers. The question about your roast is not hypothetical and it will be asked.

So the control is upstream and it is the only one

There is no acid, no sugar concentration, no process in the jar. The roast, or somebody else’s roast, is the kill step, and everything after it is about not recontaminating a product that has no way to recover.

References

Michigan State University, Center for Low-Moisture Food Safety. Thermal death kinetics of Salmonella in peanut butter as influenced by water activity, and the related work showing that Salmonella becomes more heat resistant as water activity falls. canr.msu.edu
Centers for Disease Control and Prevention. Multistate Outbreak of Salmonella Infections Associated with Peanut Butter and Peanut Butter-Containing Products, United States, 2008-2009. cdc.gov
United States Food and Drug Administration. Guidance for Industry: Measures to Address the Risk for Contamination by Salmonella Species in Food Containing a Peanut-Derived Product as an Ingredient. fda.gov
Written from federal regulation, FDA compliance policy and published food-safety research, not from a laboratory. The kill-step pages describe a real hazard and are a starting point for a conversation with your state department of agriculture and a process authority, not a determination that any roast you run is adequate.