High Pressure and Thermal Processing of Heat-Resistant Fungi

Heat-resistant fungi represent a formidable challenge in food and beverage preservation, as their spores can survive conventional pasteurisation and sterilisation treatments. Species such as Neosartorya, Byssochlamys and Paecilomyces produce ascospores that resist temperatures exceeding 80 °C, often leading to spoilage in fruit juices, jams and other acidic products. Combined high-pressure and thermal processing integrates hydrostatic pressures (up to 600 MPa) with moderate heat to disrupt spore integrity, inhibit germination and accelerate inactivation. Hyperbaric storage at room temperature further extends control by maintaining elevated pressures after an initial pasteurisation step, thus preventing hyphal development and mycotoxin formation. Advances in kinetic modelling—using parameters such as decimal reduction times and z-values—allow precise design of time–temperature–pressure regimes that ensure microbial safety while preserving nutritional and sensory quality. Emerging techniques, including sequential HPP-thermal cycles and pressure-assisted thermal sterilisation, have demonstrated effective reductions of at least 4–5 log units of resistant spores. These innovations carry global significance for the fruit processing, dairy and beverage industries, reducing reliance on chemical preservatives, lowering energy consumption and extending shelf life without compromising product quality.

Research from Nature Portfolio

Recent studies have demonstrated that natural plant extracts and essential oils can inhibit and alter the metabolism of heat-resistant Neosartorya spp., suggesting sustainable alternatives to chemical fungicides. Investigations screened multiple extracts against diverse fungal isolates and revealed distinct sensitivity clusters. Lavender and tea tree oils showed the strongest inhibitory effects at milligram-per-millilitre concentrations, while lower doses nevertheless impaired growth and metabolic activity. Metabolic profiling indicated a shift in nutrient uptake, with reduced amino acid and carbohydrate consumption and increased reliance on carboxylic acids under stress. Such findings support the integration of botanical agents into crop protection strategies and point to targeted interventions that complement high-pressure and thermal regimes in postharvest management.

High Pressure and Thermal Processing of Heat-Resistant Fungi publication trend

The graph below shows the total number of articles in high pressure and thermal processing of heat-resistant fungi across all publications each year (not limited to Nature Index journals).

Technical terms

Ascospore: A sexual spore produced within an ascus by certain fungi, characterised by robust walls that confer heat resistance.

High-pressure processing (HPP): A non-thermal preservation technique applying pressures up to 600 MPa to inactivate microorganisms while minimising heat damage.

Hyperbaric storage: Maintenance of food under elevated pressure at ambient temperature to suppress microbial germination and proliferation.

Decimal reduction time (D-value): The time required at a specific temperature to achieve a one-logarithm reduction in microbial population.

z-value: The temperature increase needed to reduce the D-value by a factor of ten, reflecting thermal resistance of spores.

References

1. Development Control and Inactivation of Byssochlamys nivea Ascospores by Hyperbaric Storage at Room Temperature. Foods (2023).
2. Soil-Borne Neosartorya spp.: A Heat-Resistant Fungal Threat to Horticulture and Food Production—An Important Component of the Root-Associated Microbial Community. International Journal of Molecular Sciences (2023).
3. Comprehensive antifungal investigation of natural plant extracts against Neosartorya spp. (Aspergillus spp.) of agriculturally significant microbiological contaminants and shaping their metabolic profile. Scientific Reports (2024).
4. Functionality and prevalence of trehalose‐based oligosaccharides as novel compatible solutes in ascospores of Neosartorya fischeri (Aspergillus fischeri) and other fungi. Environmental Microbiology (2014).
5. Modeling the Thermal Inactivation of Monascus ruber Ascospores Isolated from Green Olive (Arauco Cultivar) Storage Brine: An Alternative Strategy to Reduce Antifungal Chemical Agents. Foods (2024).