Study on Spore Contamination in Food Products

Spore Contamination in Food

• A study investigated the prevalence of spores in 90 food products using a multiparametric PCR-based tool.
• Most samples contained one or several of the targeted genera and species.
• Clostridium or Bacillus contamination was present in 100% of raw materials, 72% of dehydrated ingredients, and 80% of processed foods.
• Spore-forming bacteria can resist extreme conditions and remain dormant for centuries.
• The Bacillus genus is split into 18 genera, and similar rearrangements are proposed for Clostridium.
• Spore-forming bacteria are commonly found in soil and are responsible for food spoilage and food poisoning.
• Endospore-forming bacteria exhibit a wide range of phenotypic and genotypic characteristics.

Study Methodology

• DNA extraction from 10 ml of enriched food samples.
• Enrichment step validated by streaking on different agar media (PCA, RCM, Mossel).
• Samples incubated under different conditions optimized for the germination and growth of specific bacterial types (aerobic, anaerobic, mesophilic, thermophilic).
• Identification of cultivable strains of Bacillus cereus through 16S rRNA gene sequencing.

Spore Contamination Results

• Most analyzed products were contaminated with Bacillus genera, with 30-40% of products contaminated with both Clostridium and Bacillus.
• Other thermophilic genera, such as Anoxybacillus and Geobacillus, were detected in some processed dairy products and canned foods.
• The most frequently encountered Bacillus species were B. cereus, B. subtilis, and B. licheniformis.
• B. sporothermodurans found only in milk and dairy products.
• The psychrotolerant B. weihenstephanensis-B. mycoides was detected in all three food categories but with a higher occurrence in egg-based products.

Spore Contamination and Food Spoilage

• The presence of spores in food can lead to spoilage activity.
• A variety of spore formers can be detected in food without visible spoilage.
• Typical spoilage activity like sweet curdling, bitty cream, and flat sour spoilage were not reported in the tested samples.

Factors Affecting Spore Resistance and Growth

• Harsh conditions encountered during processing might strongly influence the spore resistance and growth ability of foodborne contaminants.
• 100% of raw materials with no visible spoilage were contaminated with Clostridium or Bacillus.
• Other thermophilic contaminants, such as A. flavithermus, Geobacillus, Stearothermophilus, Thermoanaerobacterium, and Moorella, were also present.

Spore Contamination in Raw Milk

• The impact of environmental conditions on foodborne spore diversity in raw materials has been largely studied in raw milk quality.
• Efficient control of silage fermentation and hygienic farm management can reduce transmission of environmental spores in farm tank milk and minimize the presence of aerobic and anaerobic spores in raw milk.

Adaptation of Endospore-Forming Bacteria

• The presence of endospore-forming bacteria in modern food industries may be an adaptation or selection to the man-made competitor-free ecological niche.