Impact of sodium chloride and carbon dioxide on conidial germination and radial growth of Penicillium camemberti

Penicillium camemberti is a domesticated species adapted to the dairy environment, which is used as adjunct cultures to ripen soft cheeses. A recent population genomics analysis on P. camemberti revealed that P. camemberti is a clonal lineage with two varieties almost identical genetically but with contrasting phenotypes in terms of growth, color, mycotoxin production and inhibition of contaminants. P. camemberti variety camemberti is found on Camembert and Brie cheeses, and P. camemberti variety caseifulvum is mainly found on other cheeses like Saint-Marcellin and Rigotte de Condrieu. This study aimed to evaluate the impact of water activity (aw) reduced by sodium chloride (NaCl) and the increase of carbon dioxide (CO2) partial pressure, on conidial germination and growth of two varieties of P. camemberti: var. Camemberti and var. Caseifulvum. Mathematical models were used to describe the responses of P. camemberti strains to both abiotic factors. The results showed that these genetically distant strains had similar responses to increase in NaCl and CO2 partial pressure. The estimated cardinal values were very close between the strains although all estimated cardinal values were significantly different (Likelihood ratio tests, pvalue = 0.05%). These results suggest that intraspecific variability could be more exacerbated during fungal growth compared with conidial germination, especially in terms of macroscopic morphology. Indeed, var. Caseifulvum seemed to be more sensitive to an increase of CO2 partial pressure, as shown by the fungal morphology, with the occurrence of irregular outgrowths, while the morphology of var. Camemberti remains circular. These data could make it possible to improve the control of fungal development as a function of salt and carbon dioxide partial pressure. These abiotic factors could serve as technological barriers to prevent spoilage and increase the shelf life of cheeses. The present data will allow more precise predictions of fungal proliferation as a function of salt and carbon dioxide partial pressure, which are significant technological hurdles in cheese production.

Characterization of microbial population of breba and main crops (Ficus carica) during cold storage: Influence of passive modified atmospheres (MAP) and antimicrobial extract application

The purpose of this work was to study the changes of bacterial and fungal population of breba fruits such as 'Banane' and 'San Antonio' as well as 'Cuello Dama Negro', 'Cuello Dama Blanco' and 'San Antonio' fig cultivars stored in passive modified atmospheres (MAP) by the use of three different microperforated films (M10 with 16 holes; M30 with five holes and M50 with three holes). Moreover the effects of the application of aqueous soy polyphenolic antimicrobial extract (APE), alone or combined with MAP, were also studied for 'Cuello Dama Negro' and 'Cuello Dama Blanco' fig cultivars. Bacteria and fungi isolates were identified by PCR-RFLP of 16S rRNA and ITS regions, respectively, and subsequently sequence of the different patterns obtained. The results indicated that Pseudomonas gessardii, Pantoea agglomerans and Enterobacter asburiae were the main species of bacteria found in all the treatments studied. The fungal species identified were Aureobasidium pulullans, Cladosporium cladosporioides and Alternaria alternata, which were found in a lower percentage in fruit stored in MAP and fruits treated with antimicrobial extracts, as this treatments allowed to reduce the microbial growth of moulds and yeasts. Thus, the application of treatments such as M30, M50 or the combination of MAP with antimicrobial extract was highly effective to control fruit spoilage in fig and breba crops.

Physiological behavior and quality of fresh ginseng stored in modified atmospheres generated by several package films

Physiological behaviors and quality attributes of fresh ginseng (Panax Ginseng) stored in modified atmospheres generated by several package films were investigated. The chemical compositions were also measured before and after storage. The respiration rates of fresh ginseng were inhibited effectively by film package, especially in package with lower gas permeability coefficient film. The polyphenol oxidase (PPO) activity reduced markedly and high Hunter L (*) value was maintained. Significant differences (p < 0.05) in firmness, weight loss, decay rate and pectin content were found between 0.10 mm packages and 0.05, 0.07 mm packages after 5 months of storage. The best quality parameters of fresh ginseng were obtained from the combination of 0 °C-0.10 mm. Significant difference (p < 0.05) in total saponin content was not found, and the highest total saponin content was also obtained from the combination of 0 °C-0.10 mm. The content of total sugar and reducing sugar increased significantly (p < 0.05), especially for package film with higher gas permeability coefficient. The storage life of fresh ginseng was extended significantly by film packages to 5 months with good quality and lower decay rate, especially for package film with low gas permeability coefficient.

Effects of temperature and modified atmospheres on diapausing 5th instar codling moth metabolism

The oxygen and capacity limitation of thermal tolerance (OCLTT) has been established in aquatic insect larvae, but OCLTT has not been shown to generally apply to terrestrial insects. Previous research indicates that heat treatments in combination with high concentrations of carbon dioxide and low concentrations of oxygen may be effective for controlling diapausing codling moth, a quarantine pest in walnuts, but treatment requires long times and the killing mechanism is unknown. In this study, the effects of temperature and modified atmospheres on metabolism in diapausing 5th instar codling moth (Cydia pomonella) was investigated with multi-channel differential scanning calorimeters, one equipped with an oxygen sensor. O2 consumption and metabolic heat rates in air were measured simultaneously at isothermal temperatures from 5 to 50°C at 5°C intervals. Both rates increased with increasing temperatures from 5 to 40°C. The ratio of metabolic heat rate to O2 consumption rate at temperatures ≤40°C shows that a portion of the metabolic heat is from normal anabolic reactions of metabolism. At 45 and 50°C in air, O2 consumption and metabolic heat rates dropped to near zero. These results indicate that treatment of walnuts in air at >45°C for a short period of time (minutes) is effective in killing diapausing 5th instar codling moth larvae. Continuous heating scans at 0.4°C/min were used to measure metabolic heat rates from 10 to 50°C with air and modified atmospheres with lowered oxygen and high carbon dioxide. A rapid increase was observed in heat rates above 40°C in scans with O2≥11%. Taken together with the isothermal results showing no metabolic heat production or oxygen uptake at 45 and 50°C, these results demonstrate that thermal damage to cell membranes and loss of control of oxidation reactions is the lethal mechanism at high temperature when O2≥11%. The data from scans with O2≤2% and high CO2 show the effects of oxygen limitation as postulated by the OCLTT. However, CO2 anesthesia appears to protect larvae from oxygen limitation at high temperature. These results show that treatment of walnuts in air at temperatures >45°C will rapidly kill diapausing 5th instar codling moths.