Fact sheet on lactic acid bacteria (LAB)

Lactic acid bacteria (LAB) are a group of several bacterial genera that can ferment sugars to lactic acid. These include, for example, the genera Lactobacillus, Lactococcus, Streptococcus, Leuconostoc, and Bifidobacterium.

Many strains are deliberately used in food production as starter and protective cultures or as probiotic cultures. However, in many food groups they also play a role as spoilage organisms, for example in fresh meat, heat-treated meat products, fish and fish products, delicatessen products, as well as fruit and vegetable juices.

Characteristics

• Cocci-shaped or rod-shaped bacteria
• Gram-positive
• Oxidase-negative (generally)
• Catalase-negative

Origin / Occurrence

• LAB occur at only a few natural habitats due to their high nutrient requirements (e.g., soil, wastewater, orchards, mammals…)
• In humans and animals they are natural residents of the intestinal tract, the skin and the mucous membranes
• LAB are also present on the surfaces of many plant-derived foods (e.g., fruits and vegetables), and in raw milk from cows, goats and sheep

Importance

• LAB are deliberately used in some foods as "fermenters", such as in yogurt, quark, many types of cheese, sourdough, sauerkraut and raw sausage. → Elevated counts of LAB are to be expected and are desirable in these foods. The aerobic mesophilic count (total viable count) is therefore, alongside LAB, correspondingly high in these products and cannot be evaluated as a hygiene or spoilage parameter
• Lactic acid fermentation lowers the pH value, which can inhibit the growth of other bacteria. This fermentation effect is decisive for the flavor and shelf life of these foods
• LAB can also play a role as spoilage organisms if fermentation becomes uncontrolled. The product can become overly acidic, develop off-flavors or gas formation and thus spoil.

Growth conditions

• Temperature:
  • Optimum: +30 °C to +40 °C
  • Minimum: +10 °C (depending on the strain)
  • Generally no growth above +50 °C
• pH: growth at pH 4.0 to 6.5 (exceptions even down to pH 3.0)
• aw: growth at a water activity of at least 0.94
• Oxygen requirement: aerotolerant, anaerobic metabolism

Inactivation by heat

• At +72 °C for at least 2 minutes exposure time (note: check core temperature). There are some exceptions that can survive high temperatures. However, they are by far not as heat-resistant as spores.

1. Check the implementation of cleaning and disinfection:
   1. Hygiene plan
   2. Execution of cleaning and disinfection, e.g., dosing of disinfectant, contact time, use of suitable and clean materials and cleaning cloths
2. Avoid residual moisture and biofilms. Ensure good drying of equipment, utensils and surfaces
3. Train staff regarding potential errors and improvement measures
4. Repeat cleaning and disinfection
5. Verify effectiveness by visual on-site inspections, environmental testing and follow-up examinations

1. Request cold-chain traceability from the supplier for transport
2. Check incoming and storage temperatures
3. Monitor cooling temperatures / cold chain during processing, transport and sale
4. If overage (or excessive shelf life) is suspected, perform appropriate storage tests
5. Verify effectiveness through follow-up testing

1. Check processes, production records and documentation
2. Inactivation of most bacteria at a core temperature of +72 °C for at least 2 minutes. Exceptions are, for example, heat-stable spores and toxins. In these cases significantly higher temperatures and exposure times are required. For further information see the respective information sheets (profiles)
3. Verify correctness of processes and temperatures
   1. In general, hot-holding temperatures above +60 °C are required
   2. Rapid cooling: after 3 hours a core temperature of at least +7 °C must be reached (special care is required for large quantities)
4. Verify effectiveness through follow-up testing

1. Check work organization in the facility
   1. Separate work areas, equipment and utensils for raw and processed foods
   2. Separation of "clean" and "unclean" areas and activities
2. Train staff regarding potential errors and improvement measures
3. Verify effectiveness through visual on-site inspections and follow-up testing

1. Inspect products on receipt for e.g., incoming/transport temperature, shelf life, packaging, deviations or abnormalities
2. The same applies to goods before use in production. In case of doubt, do not use the food and consult a supervisor
3. Check microbiological specifications. If necessary, arrange laboratory testing of suspicious products or request results from the supplier
4. Verify effectiveness through follow-up testing

1. Check processes, environmental conditions, production records and documentation
2. Verify effectiveness through follow-up testing