Modeling the Effect of Modified Atmospheres on Conidial Germination of Fungi from Dairy Foods

Abstract

Modified atmosphere packaging (MAP) is commonly applied to extend food shelf-life. Despite growth of a wide variety of fungal contaminants has been previously studied in relation to modified-atmospheres, few studies aimed at quantifying the effects of dioxygen (O2) and carbon dioxide (CO2) partial pressures on conidial germination in solid agar medium. In the present study, an original culture method was developed, allowing microscopic monitoring of conidial germination under modified-atmospheres in static conditions. An asymmetric model was utilized to describe germination kinetics of Paecilomyces niveus, Mucor lanceolatus, Penicillium brevicompactum, Penicillium expansum, and Penicillium roquefoti, using two main parameters, i.e., median germination time (τ) and maximum germination percentage (Pmax). These two parameters were subsequently modeled as a function of O2 partial pressure ranging from 0 to 21% and CO2 partial pressure ranging from 0.03 to 70% (8 tested levels for both O2 and CO2). Modified atmospheres with residual O2 or CO2 partial pressures below 1% and up to 70%, respectively, were not sufficient to totally inhibit conidial germination,. However, O2 levels < 1% or CO2 levels > 20% significantly increased τ and/or reduced Pmax, depending on the fungal species. Overall, the present method and results are of interest for predictive mycology applied to fungal spoilage of MAP food products.

Dynamics of the Apple Fruit Microbiome after Harvest and Implications for Fruit Quality

“…Our data suggest that a further optimization, tailored specifically to the inhibition of fungal genera, could lead to an improved suppression of pathogenic fungi and thus to a reduction of food losses due to spoilage. This has been shown, for example, in dairy products [ 47 , 48 ] but to our knowledge not in fruits. In addition, microbiome studies can inform the effectiveness of and assist in improving postharvest methods such as washing and waxing [ 18 ].…”

High sorbic acid resistance ofPenicillium roquefortiis mediated by the SORBUS gene cluster

“…roqueforti is often encountered as a spoilage organism of food and feed. This can partly be attributed to its ability to grow at refrigeration temperatures [23], low O 2 levels [24] and/or its resistance to preservatives, such as sorbic acid [25]. The inhibitory effect of propionic, benzoic and sorbic acid on P. roqueforti growth was assessed and benzoic acid was found to have the strongest inhibitory effect on 34 P. roqueforti strains.…”

Heterogeneity of food spoilage fungi

“…roqueforti is often encountered as a spoiling contaminant in food. This can partly be attributed to its ability to grow at refrigeration temperatures (Kalai et al, 2017), low O2 levels (Nguyen Van Long et al, 2017b) and its resistance to preservatives, such as sorbic acid (Quattrini et al, 2019). The inhibitory effect of propionic, benzoic and sorbic acid on P.…”

“…In nature, it is also known to be a saprophytic fungus degrading dead organic material (Coton et al, 2020;Samson et al, 2010). The ability of P. roqueforti to grow at high CO2 concentrations (up to 84.8 %), low O2 levels (as low as 0.3 %), and at low temperature (as low as 0 °C) distinguishes this species from other filamentous fungi (Kalai et al, 2017;Nguyen Van Long, et al, 2017b). After a period of vegetative growth, P. roqueforti forms conidia that are distributed via the air.…”

“…A fungus that is capable of overcoming these hurdles is P. roqueforti. This can be attributed to its ability to grow at refrigeration temperatures (Kalai et al, 2017), at low O2 levels (Nguyen Van Long et al, 2017b) and its resistance to biological and chemical preservatives, such as sorbic acid (Quattrini et al, 2019).…”