FSIS-GD-2023-0002

Degree-hours

Hours above 60 F multiplied by the degrees above it, accumulated until the product reaches pH 5.3, which is the accounting FSIS uses to limit Staphylococcus aureus growth during fermentation.

FSIS defines degree-hours as the amount of time in hours above 60 F, the critical temperature at which staphylococcal growth effectively begins, that a fermentation can take at a given temperature to reduce the pH to 5.3 or below in order to control S. aureus growth.

Degrees are the excess over 60 F. Degree-hours are degrees multiplied by hours, computed for each temperature the fermentation passes through and summed. The count stops when the pH target is reached.

Definition

Base temperature: 60 F
Count until: pH 5.3 or below
Controls: Staphylococcus aureus
Standard: no more than 2 log growth

FSIS Ready-to-Eat Fermented, Salt-Cured, and Dried Products Guideline, FSIS-GD-2023-0002.

The one ceiling that can be derived

Derived, not transcribed

900 degree-hours

110 F less the 60 F base is 50 degrees. 50 degrees for 18 hours is 900 degree-hours. FSIS calls 18 hours at 110 F the maximum allowable, so 900 degree-hours is what that sentence means at that temperature. FSIS does not itself publish a table of maxima.

FSIS-GD-2023-0002, Ready-to-Eat Fermented, Salt-Cured, and Dried Products Guideline

Calculate

Stage 1 temperature (F)

Stage 1 duration (hours)

Degree-hours accumulated

180

Working

Degrees are the excess over 60 F. The count runs until
the product reaches pH 5.3 or below.

stage 1: (75 - 60) x 12.0 h = 180
total  = 180 degree-hours

This site does not print a maximum. FSIS does not publish one: it points at an American Meat Institute document for the limits, and that document is not a government publication. The one ceiling that can be read out of an FSIS text is 900 degree-hours, and that is a derivation, set out on this page.

Worked example

12 hours at 75 F, then 10 hours at 85 F, pH reaching 5.3 at the end.

stage 1: (75 - 60) x 12 = 180
stage 2: (85 - 60) x 10 = 250
total                   = 430 degree-hours

What this does not tell you

FSIS does not publish a table of maximum degree-hours. It points at an American Meat Institute document, which is not a government publication. The maxima that circulate widely are not printed on this site as FSIS figures, because they are not.
Meeting degree-hours controls S. aureus and nothing else. FSIS answers the question directly: no, meeting degree-hours is not enough to show the biological hazards are addressed.