Microbiological modelling of sanitation in post-harvest storage areas

Global warming, loss of fertile soils and reduction of spring waters make the agriculture difficult day by day. While the fertile soils are even lost with precipitations and with the water resources running low, it will have been harder to reduce the production of agricultural products. Therefore accessing of the healthy food is getting difficult, where as the growing need of food deepens this problem with the parellel increase of the population. On the other hand, only average of 50 % of the crops that harvested from the farmlands can get to the markets. Most of the loss is caused by the microorganisms. It is necessary to prevent the losses in agricultural products whose production cannot be increased. In this context, the naming of environmental isolates, which are frequently encountered in the postharvest warehouses, using microbiological and molecular techniques, and their behavior against sanitation in vitro conditions were modeled. Effective doses of water-based trimethoxyl quat (SilQUAT) compound against environmental isolates were determined and the difference of the effective doses for standard strains has been demonstrated. The effectiveness of three different doses, in clean and dirty conditions, was determined in 1 and 5 minutes for the isolated bacteria strains with the BS EN 1276:2019 test method and in 15 and 60 minutes for the isolated fungi strains with the BS EN 1650:2019 test method. Besides that post-application persistence of SilQUAT compound was tested with EPA (Environmental Protection Agency)#01 Protocol (2007). In comparison with the environmental isolates, Gram positive Staphylococcus aureus, Gram negative Escherichia coli, Candida albicans yeast, Aspergillus niger mold were selected as representative organisms among the standard strains. The minimum inhibitory concentrations (MIC) of SilQUAT compound for bacteria were determined as 5-200 mg/L; the minimum bactericidal concentrations (MBC) were determined as 10-200 mg/L. The MIC values for yeast fungus isolates were 3-5 mg/L and the minimum fungicidal concentration (MFC) values were 40-50 mg/L, while the MIC and MFC values for mold fungus isolates were 40-400 mg/L. According to BS EN 1276: 2019 standard, reduction of 5 log, which is the effective biocide criteria, was provided in 5-minute contact time at the concentration of 50 mg/L of the biocide in clean and dirty conditions for 6 bacteria isolates; at the concentration of 75 mg/L for 10 bac concentration of 100 mg / L for 10 bacterial isolates for 14 bacterial isolates. While BS EN 1650:2019 provides 4 log effective biocide criteria for all yeast isolates at 15 minutes contact time in clean/dirty conditions at all tested biocide doses; it was provided for 8 mold isolates at 125 mg/L in 60 min contact time in clean/dirty conditions; for 10 mold isolates at 150 mg/L and for 15 mold isolates at 200 mg/L of concentration. Environmental isolates were found to be more resistant than standard representative organisms. According to the EPA protocol, SilQUAT compound treated PVC (polyvinyl chloride), stainless steel and glass surfaces showed a strong antimicrobial effect compared to the control after 12 etchings and 5 reinoculations, killing > 99.9% of the microorganism mixtures. It was determined that SilQUAT compound, which etching on different surfaces did not cause loss in the activity of the biocide, was durable and permanent against mechanical cleaning processes. Product loss can be prevented by removing the accumulated microbial load that comes with the products in the postharvest storages and by ensuring the permanence of sanitation. In addition, the biocide used in the study will minimize secondary environmental pollution by preventing the use of biocides at higher concentrations than necessary due to the fact that it does not leave any residual compounds in the water and affects different organism groups at low dosages. SilQUAT compound, whose effectiveness and permanence has been verified against the native flora of the postharvest storage, can be recommended to be used in postharvest storage areas to prevent microbial load.