Fermenting Salami: Temperature, Humidity, pH and the Degree-Hour Limit

Last updated November 2, 2026.

Fermentation is the step where your salami turns sour, and it's a safety step first. BCCDC puts it plainly: "It is key for the pH of the product to be lowered to 5.3 quickly enough to limit the amount of enterotoxin produced" (BCCDC 3.13). The full recipe lives in How to make salami at home. This page goes deep on the fermenting step.

Why fermentation matters for safety (and what it doesn't do)

The bug in question is Staphylococcus aureus. BCCDC says its toxins "can only be produced at temperatures above 15.6°C (60°F) AND if the pH of the product has not yet reached 5.3" (BCCDC 3.13). So the race is simple. Get the pH down to 5.3 before the meat spends too long warm.

This part's serious. pH 5.3 is the S. aureus control point, not a kill step. FSIS says "Degree-hours are intended to control the outgrowth of S. aureus. To reduce levels of other pathogens such as Salmonella, products often need to be fermented to a lower pH than 5.3" (FSIS-GD-2023-0002).

Starter cultures and sugar

Use a culture. BCCDC says "Fermentation requires lactic acid bacteria (LAB) commercial starter culture," and that "Spontaneous (natural, wild) fermentation of meats is not recommended, as the time required for pH drop may allow growth of unacceptable bacteria." Backslopping, meaning reusing a previous batch, "is also not recommended" (BCCDC 3.13). BCCDC also says the starter "is not outdated and that it has been stored according to the manufacturer's instructions" is something the maker must ensure (BCCDC 3.13).

The culture needs food. AMI explains that the bacteria "convert fermentable carbohydrate (i.e., dextrose or sucrose) in the meat mixture to lactic acid, and thus lower the pH" (AMI Foundation GMP, via UW-Madison). How much sugar, and which kind, depends on your culture. BCCDC says "The type of sugar and the dose to be used varies according to the starter culture used," and "the supplier of the starter culture is the best advisor" on how to use it (BCCDC 3.13). Follow the instructions that came with yours.

Temperature and humidity in the fermenting chamber

For dry sausage, BCCDC gives a chamber temperature of "20-24°C for dry sausages," which is 68 to 75°F, "and the relative humidity should start at 95% and decrease over time, kept at 5% less than the moisture of the product" (BCCDC 3.13). So don't park it at one number. Start near 95% and step it down as the salami gives up water.

Get humidity wrong and you'll see it. BCCDC warns that "Humidity that is too low or when there is too much air movement will cause case hardening" (BCCDC 3.13). That's covered in Case hardening. Too little airflow causes the opposite problem, "wild mould growth (if air flow is too low)" (BCCDC 3.13), which we cover in Mold on salami.

Humidity comes down. Illustration, not a photo: relative humidity should start at 95% and decrease over time. The only value shown is the 95% start; the chart is not to scale and is not a schedule.

Target pH: 5.3 or below

AMI says fermented sausages "shall attain a pH of 5.3 or lower" within the degree-hour time frame (AMI Foundation GMP, via UW-Madison). You start well above that. BCCDC says the pH "of fresh meat is approximately 5.6-5.8," and that fermentation "could be accomplished in less than a day or up to 6 days, depending on temperature used and starter culture employed." On average, "Fermentation to pH 5.3 will be complete on average within 48 hours" (BCCDC 3.13).

You may see a lower number, pH 5.0, quoted for commercial semi-dry sausage. That comes from an FSIS labeling memo: "Semi-dry sausages having a moisture - protein ratio of 3.1:1 or less and a pH of 5.0 or less are shelf-stable" (FSIS Policy Memo 056, in FSIS Label Policy Memoranda). It's about commercial semi-dry products, not a home target for dry salami. We mention it so it doesn't confuse you.

The degree-hour limit, explained

Degree-hours put a cap on how long the meat can sit warm before it reaches pH 5.3. FSIS explains: "Degrees are measured as the excess over 60°F (15.6°C). Degree-hours are the product of time at a particular temperature and the 'degrees.'" The limit "depends upon the highest temperature in the fermentation process prior to the time that a pH of 5.3 or less is attained" (FSIS-GD-2023-0002).

In Fahrenheit, AMI's limits are "Fewer than 1200 degree-hours when the highest chamber temperature is less than 90°F," "Fewer than 1000 degree-hours when the chamber temperature is between 90 and 100°F," and "Fewer than 900 degree-hours when the chamber temperature is greater than 100°F" (AMI Foundation GMP, via UW-Madison).

If you work in Celsius, use BCCDC's numbers instead. It says degree-hours "must not exceed 665 degree-hours when the highest fermentation temperature is <33°C" (BCCDC 3.13), with 555 between 33° and 37°C and 500 above 37°C. These are the same rule as AMI's, just counted in Celsius degrees. Our arithmetic: a Celsius degree is 1.8 Fahrenheit degrees, so 665 × 1.8 is about 1197, which is AMI's 1200. Pick one unit and stick with it for the whole batch.

Here's AMI's own example, in Fahrenheit: "Constant 80°F for 55 hours with a pH decline to 5.3," which works out to "(20) x (55) = 1100 degree-hours," so "Process A passes the guideline (Limit: 1200 degree-hours)" (AMI Foundation GMP, via UW-Madison). AMI's table also shows that at a 75°F chamber you get at most 80 hours to reach pH 5.3 (AMI Foundation GMP, via UW-Madison). If your chamber shifts temperature, FSIS says degree-hours "are calculated for each temperature used during fermentation" (FSIS-GD-2023-0002), so add up each stretch.

How to measure pH

You need real readings, not a guess. AMI says "pH readings must be taken from each lot," and "It is important to record all pH measurements before the product surface temperature reaches 110°F or before the degree/hour limitation has been reached" (AMI Foundation GMP, via UW-Madison). BCCDC tells operators to "take pH readings" and keep records in log sheets, and its Appendix 1 includes a calibration log (BCCDC 3.13). Use a meter, keep it calibrated, and write down every reading with the time.

We're not giving step-by-step home testing instructions here. We didn't find a source we trust for that yet, so follow your meter's instructions.

What to do if pH doesn't drop

BCCDC is blunt about missing the target: "If the degree-hours standard is not met, then we cannot be assured that the product will be safe" (BCCDC 3.13). Commercial plants have a fallback. AMI describes sending samples to a lab, where "Positive thermonuclease readings would strongly indicate that a product should be destroyed" (AMI Foundation GMP, via UW-Madison). At home there's no lab.

If the pH hasn't reached 5.3 by the degree-hour limit, throw the batch out.

For next time, check your culture. BCCDC says it must not be "outdated" and must be "stored according to the manufacturer's instructions" (BCCDC 3.13). We won't list other causes. Our sources don't name them, and we won't guess.

After fermentation

BCCDC says that when the sausage "has reached a pH of 5.3 or below, with a calculated degree-hours that did not exceed the maximum permitted degree-hour limit, then the fermentation stage is complete." Then: "If not further processed at this point, the sausages must be refrigerated within 6 hrs or frozen" (BCCDC 3.13).

Most salami goes on to drying. BCCDC says dry sausages are "dried in a drying chamber/room after fermentation to reduce aw to 0.9 or below" (BCCDC 3.13). How long that takes depends partly on your casing, so see How to choose a salami casing.

When in doubt, throw it out.

Sources

Read our disclaimer. This page is general education, not professional food-safety advice.