Heat resistance of Paenibacillus polymyxa in relation to pH and acidulants

Area of Science:

• Food Microbiology
• Food Chemistry
• Bacterial Spore Resistance

Background:

• Paenibacillus polymyxa spores exhibit significant heat resistance, posing challenges for food preservation.
• Understanding factors that reduce spore heat resistance is crucial for effective microbial control in food processing.

Purpose of the Study:

• To evaluate the efficacy of various organic acids in reducing the heat resistance of Paenibacillus polymyxa spores.
• To investigate the correlation between the concentration of undissociated organic acids and the decreased heat resistance of spores.

Main Methods:

• Testing heat resistance of P. polymyxa spores in distilled water and milk across different temperatures (85-95°C) and pH (4).
• Utilizing lactic, citric, and acetic acids, along with their sodium salts, at varying concentrations (50-200 mmol l⁻¹).
• Quantifying the decrease in D-values (decimal reduction time) under different treatment conditions.

Main Results:

• The undissociated form of organic acids significantly increased spore heat sensitivity.
• Lactic acid demonstrated the highest efficacy in reducing heat resistance.
• A non-linear relationship was observed, with decreasing D-values ranging from 43% to 74% at 50 mmol l⁻¹ undissociated acid.

Conclusions:

• The undissociated fraction of organic acids effectively increases the heat sensitivity of Paenibacillus polymyxa spores, even in complex matrices like milk.
• Predicting undissociated acid concentrations based on substrate properties can optimize heat treatment lethality.
• Findings support the food industry in enhancing thermal process efficacy and potentially reducing processing times.