Starter Cultures for Salami: What They Do and How to Use Them
A dry salami is never cooked. Acid from fermentation does much of the early safety work, and a starter culture is what makes that acid. New Zealand's MPI defines a starter culture as "a commercial preparation of microorganisms for fermenting the batter" (MPI UCFM guidance). This page covers what's in one, why the agencies want you to use one, and how to handle it. For the full process, see How to make salami at home.
What a starter culture is
Most of the work is done by lactic acid bacteria. MPI explains that "lactic acid bacteria from the starter culture use sugars within the meat and sugar added to the batter to produce acid which lowers the pH of the batter and prevents the growth of pathogenic bacteria" (MPI UCFM guidance).
BCCDC lists what a culture can contain: "Lactic acid bacteria (LAB): commercial source recommended. Other starter cultures may include Micrococci and Pediococci" (BCCDC 3.13).
Some cultures are there for color and flavor. BCCDC says "Micrococcus bacteria convert nitrate to nitrite and have been used for a long time as a starter culture in salami because of their contribution to development of curing colour and flavour" (BCCDC 3.13). The acid makers add flavor too. MPI notes that "the starter culture also produces flavour compounds, enzymes, and other compounds which prevent the growth of other bacteria" (MPI UCFM guidance).
Why not rely on wild fermentation
Meat already carries some lactic acid bacteria, and salami used to be made that way. The agencies are blunt about it now. The AMI guidance calls natural fermentation "highly unreliable" and says it "should not be used" (AMI Foundation GMP). BCCDC says "Spontaneous (natural, wild) fermentation of meats is not recommended, as the time required for pH drop may allow growth of unacceptable bacteria" (BCCDC 3.13).
FSIS explains what goes wrong: "in the absence of a starter culture Salmonella, STEC, and other undesirable microorganisms will instantly become the dominant microflora." It lists why a culture helps: "Microbial competition," "Production of lactic acid which lowers the product pH and inhibits the growth of pathogenic bacteria," and "Possible production of bacteriocins" (FSIS-GD-2023-0002).
Backslopping means using a piece of the last batch to start the next one. BCCDC says it is "NOT RECOMMENDED for small operators who cannot conduct routine pH and microbiological tests," because it "may amplify pathogen loads if the culture becomes contaminated" (BCCDC 3.13). MPI says plainly: "You must not use back slopping" (MPI UCFM guidance).
AMI names the method it prefers: "a commercially prepared culture which is handled and used as prescribed by the manufacturer" (AMI Foundation GMP).
Use a commercial starter culture. Don't use wild fermentation or backslopping.
Reaching pH 5.3 in time
The culture has a deadline. BCCDC says "the pH drop within degree-hour requirements must be achieved to control Staphylococcus aureus if fermentation is performed above 15.6°C" (BCCDC 3.13).
AMI counts degrees as "the excess over 60°F," and sets the limit by the highest temperature before pH 5.3. Processes under 90°F get 1200 degree-hours, those above 89°F get 1000, and those above 100°F get 900 (AMI Foundation GMP). We work through the math in Fermenting salami, and explain the numbers in pH and water activity explained.
How fast the pH falls isn't fixed. MPI says it depends on "the number and type of lactic acid bacteria in the starter culture," "the fermentation temperature," and "the amount and type of fermentable sugar" (MPI UCFM guidance).
Acidifiers such as GDL can help, but BCCDC calls them "an optional aid in addition to use of LAB starter culture" (BCCDC 3.13).
pH 5.3 is not a kill step. AMI says reaching it "is insufficient to destroy E. coli O157:H7 without a cook step" (AMI Foundation GMP).
If the pH hasn't reached 5.3 by the degree-hour limit, throw the batch out.
Warm and cool cultures
Cultures are made for different temperatures. MPI says "individual culture strains may work best at different temperatures and tolerances" (MPI UCFM guidance).
BCCDC describes the two usual patterns. Semi-dry sausages ferment warmer, "between approximately 25oC to 45oC," which takes "less than 24 hours or up to 2 days to reach pH 5.3 or less." Most aren't dried afterward, so BCCDC says "these sausages require refrigeration." Dry sausages ferment cooler, "20oC to 24oC," usually "48 hours but up to 6 days to reach pH 5.3 or less" (BCCDC 3.13). BCCDC adds that you "should refer to starter culture manufacturer instructions for optimal fermentation temperatures."
If your cure uses nitrate for a long dry, the culture matters too. BCCDC says nitrate is for products needing "3 weeks or longer" and "should be used with a micrococcus starter culture" (BCCDC 3.13).
Handling the culture
Treat it as a living ingredient. BCCDC says the starter must be "not outdated" and "stored according to the manufacturer's instructions" (BCCDC 3.13). MPI says the supplier's storage and shelf life instructions "should be strictly followed" (MPI UCFM guidance).
Follow the maker on how to add it. MPI lists what those instructions should cover: the "reconstitution method (e.g. some freeze-dried cultures have to be dissolved in distilled water for about 30 minutes before adding into the batter mix)," the "amount of starter culture to be added to any given amount of batter," the "type and amount of fermentable sugars to be added," and the "fermentation temperature" (MPI UCFM guidance).
Some things slow a culture down. BCCDC says "additions of 4% or higher salt may inhibit the bacterial culture" (BCCDC 3.13). MPI says adding alcohol "can inhibit the starter culture" (MPI UCFM guidance).
Mold cultures
A mold culture works on the outside of the salami. FSIS says "Sometimes a commercial mold culture will be added prior to fermentation to actively apply a live mold culture to prevent the growth of undesirable molds and for flavor development." It's applied "by dipping or spraying the sausage casing," and the mold "may result in more uniform drying with less chance for case hardening," though it can also mean "slower drying" (FSIS-GD-2023-0002). A mold culture does not replace the starter culture inside.
For telling good mold from bad, see Mold on salami. For the dry outer ring, see Case hardening.
When in doubt, throw it out.
Sources
Read our disclaimer. This page is general education, not professional food-safety advice.