Inhibition or Stimulation of Ochratoxin A Synthesis on Inoculated Barley Triggered by Diffuse Coplanar Surface Barrier Discharge Plasma

Abstract

Ochratoxin A (OTA) is one of the most abundant food-contaminating mycotoxins. Besides their high toxicity, mycotoxins are highly stable to physical, chemical or biological detoxification. Therefore, the treatment with cold atmospheric plasma could be one approach to reduce the amount of mycotoxins in different products. The aim of this study was to determine the influence of cold atmospheric plasma on the inactivation of Aspergillus niger and Penicillium verrucosum inoculated on barley and their production of OTA. Inoculated barley was treated with plasma generated by dry air, CO2 or CO2 + O2 for 1 or 3 min and stored for up to two weeks at 9, 25, or 37°C. Three minutes of air plasma treatment effectively significantly reduced the total mold count of both microorganisms by 2.5–3 log cycles. The production of OTA from A. niger was only low, therefore the treatment effect was indistinguishable. The treatment of P. verrucosum on barley after an incubation of five days using a CO2 + O2 plasma resulted in a reduction of the OTA content from 49.0 (untreated) to 27.5 (1 min) and 23.8 ng/g (3 min), respectively. In contrast, CO2 plasma caused an increase of the OTA amount from 49.0 (untreated) to 55.8 (1 min) and 72.9 ng/g (3 min). Finally, the use of air plasma resulted likewise in a decrease of the OTA concentration from 56.9 (untreated) to 25.7 (1 min) and 20.2 ng/g (3 min), respectively. Reducing the incubation time before the treatment to 24 h caused in contrast an increase of the OTA content from 3.1 (untreated) to 29.1 (1 min) and 20.7 ng/g (3 min). Due to the high standard deviation, these changes were not significant, but the tendencies were clearly visible, showing the strong impact of the plasma gas on the OTA production. The results show, that even if the total mold count was reduced, under certain conditions the OTA amount was yet enhanced, probably due to a stress reaction of the mold. Concluding, the plasma gas and incubation conditions have to be considered to allow a successful inactivation of molds and in particular their toxic metabolites.

Cold plasma for the disinfection of industrial food‐contact surfaces: An overview of current status and opportunities

“…Nevertheless, it has been shown that CAP treatment might lead to an increase of toxin prodcution in some cases, possibly due to the stress response mechanisms initiated by the microorganisms that produced it (e.g., using an air SBD in combination with cold stress for removal of Ochratoxin A). However, the increased variance errors observed in this study might explain those results (Durek et al, 2018). In another study, an N 2 &O 2 MW yielded 61-93% reduction of prions on PS within 40 min, depending on initial concentration (Elmoualij et al, 2012).…”

Enhancing the Efficacy of Microwave Blanching-cum-black Mould Inactivation of Whole Garlic (Allium sativum L.) Bulbs Using Ultrasound: Higher Inactivation of Peroxidase, Polyphenol Oxidase, and Aspergillus niger at Lower Processing Temperatures

“…European Union countries have imposed limits on OTA content in coffee and foods, in some cases as stringent as 5 ng/g (Bayman et al, 2002 ). Durek et al ( 2018 ) reported that OTA production by Aspergillus niger (inoculation with a mycelium suspension) of 5.32 ± 0.02 log CFU/g and 2.32 ± 0.58 log CFU/g was 0.16 ng/g and 0.9 ng/g, respectively. They found that in barley inoculated with spore suspension, Aspergillus niger of 4.6 log CFU/g and 2.4 log CFU/g produced OTA of 0.1 ng/g and 0.06 ng/g, respectively.…”

Comparative analysis of the germination of barley seeds subjected to drying, hydrogen peroxide, or oxidative air plasma treatments

“…A central hypothesis of this study is that peroxo-like species may affect the ABA and thus induce changes in dormancy and, consequently, germination rate. [23][24][25][26][27][28][29][30][35][36][37][38][39][40][41][42][43][44][45]48] It is, therefore, important to assess the content of peroxo-like species incorporated in the seeds after their treatment with a plasma of air or with a solution of H 2 O 2 . The peroxo-like content in the seeds was estimated by means of the classical colorimetric procedure proposed by Soares et al [50] According to this procedure peroxo-like species formed or incorporated into the seeds can be extracted by applying the following procedure: (i) grinding 1 g of seeds in a 10 ml phosphate-buffered solution (50 mmol l −1 , pH=6,5) with 1 mmol l −1 hidroxilamine; (ii) the resulting slurry is then centrifuged at 6.000 g n for 25 min; (iii) 3 ml of the separated liquid is then mixed with a 1 ml of titanium sulfate solution at 0.1% in a volume ratio of 20%; (iv) this mixture is centrifuged at 6.000 g n for 25 min and the separated transparent liquid is then optically analyzed with a spectrometer.…”

“…Particularly for these industrial applications, any improvement in germination rate, even if meaning a small decrease in the period of time required to open the seed bark and trigger the plant rooting, may have a considerable economic impact because of an effective reduction in the malting period. [34] The enhancement of germination rate of barley seeds treated with plasmas is a widely studied case example [25,29,[35][36][37][38][39][40] where, similarly to other seeds, the found improvements in germination have been attributed to a variety of chemical and physical effects of the plasma treatments either on the surface of seeds and/or in their internal biochemistry and enzymatic activity. Herein, we investigate the effect of plasmas on the germination and growth of barley seeds and study the influence on other phenomena that may be also affected by plasma and/or other related treatments.…”