Process
Fermentation with starter cultures
Lactic acid bacteria acidify the meat, and where staphylococci are included they develop colour and flavour.
Published parameters
| Parameter | Value | Source |
|---|---|---|
| Target pH for S. aureus control | 5.3 or below | FSIS-GD-2023-0002 |
| Degree-hour base temperature | 60 F | FSIS-GD-2023-0002 |
| Derived ceiling at 110 F | 18 hours, which is 900 degree-hours | Derived from FSIS-GD-2023-0002 |
| S. aureus performance standard | no more than 2 log growth during processing | FSIS-GD-2023-0002 |
What the step is for
Lowers pH, which limits Staphylococcus aureus and contributes to the eventual lethality. It does not by itself constitute a lethality treatment.
The most consequential sentence FSIS has written about fermentation is that fermentation itself is not a particularly effective lethality treatment. Salmonella, shiga-toxin producing E. coli and Listeria all survive it, and a slow fermentation makes matters worse because the organisms become acid tolerant on the way down.
What fermentation does is control Staphylococcus aureus, and it does that by getting to pH 5.3 fast enough. Degree-hours is the accounting: degrees above 60 F, multiplied by hours, summed until the pH target is reached.
The starter culture is a hurdle in its own right, not just a fermenting agent. FSIS notes that pediocin-producing Pediococcus acidilactici reduce Listeria more effectively than non-producing strains of the same species.
Hazards this step bears on
Arithmetic for this step
Regulatory citations are to the Electronic Code of Federal Regulations, Title 9, as in force on 1 January 2026. FSIS guideline citations give the guideline identifier; the documents are listed with their URLs on methodology.