Toxin Production by Clostridium botulinum in Shelf-Stable Pasteurized Process Cheese Spreads

Area of Science:

• Food Microbiology
• Food Safety
• Microbial Spoilage

Background:

• Pasteurized process cheese spreads are often shelf-stable, raising questions about their safety regarding microbial contamination.
• Clostridium botulinum spores can survive in processed foods, posing a significant health risk if toxin production occurs.

Purpose of the Study:

• To assess the potential for Clostridium botulinum (types A and B) spore growth and toxin production in five non-refrigerated, pasteurized process cheese spreads.
• To inform regulatory decisions regarding the classification of these cheese spreads under Good Manufacturing Practice Regulations.

Main Methods:

• Selected five cheese spreads based on pH (5.05–6.32) and water activity (a_w, 0.930–0.953).
• Inoculated spreads with a mixture of Clostridium botulinum types A and B spores at high (24,000) and low (460) concentrations.
• Incubated inoculated samples at 35°C and monitored for toxin production over time.

Main Results:

• Limburger and Cheese with Bacon spreads became toxic, with Limburger showing higher average toxicity (3000 MLD/ml) than Cheese with Bacon (54 MLD/ml).
• Toxicity was observed in samples inoculated with the higher spore concentration, and notably, in one sample with the lower inoculum (460 spores).
• Incubation times for toxicity varied, with Limburger reaching toxicity at 83 days and Cheese with Bacon at 50 days (high inoculum).

Conclusions:

• Certain shelf-stable process cheese spreads can support the growth and toxin production of Clostridium botulinum.
• The findings suggest a need for careful evaluation of these products concerning potential botulism risks.
• Results may influence the regulatory classification of these cheese spreads as low-acid canned foods.