Quaternary ammonium compounds (QAC) are surface-active chemicals that are widely used for surface sanitation in the food processing industry, disinfectants, fabric softeners, and cosmetics. They are designed to remain stable and effective in water-based solutions. QACs typically are diluted with water so they can be applied in higher volumes which helps to facilitate their dispersal and allows them to interact with target surfaces or organisms. In several related lines of research funded by the California Tomato Research Institute, the California Specialty Crop Block Grant Program, and the California League of Food Processors, UC Davis researchers are evaluating QAC efficacy on broomrape seeds and soil-borne pathogens. The main goal of the experiment is to find the best equipment sanitation practices that can be used on field equipment to help reduce the risk of field-to-field spread of branched broomrape and other high-profile soil-borne pathogens in soil and plant debris.
During a recent UC Cooperative Extension field day focused on branched broomrape and equipment sanitation, a question was raised about the stability of quaternary ammonia sanitizers once diluted. Many growers currently have dedicated tanks and pressure washers used to sanitize farm equipment between fields to reduce the spread of broomrape seed and soilborne pathogens. In the discussion part of the field day, concern was expressed that the sanitizer's potency might diminish if it remained in the tank for several days. To address this concern, a preliminary experiment was undertaken, utilizing a QT-10 test paper (Hydrion) to assess the strength of quaternary compounds over time.
Three commercial QAC sanitizers, namely MG4-Quat, Flo-Quat, and Cleaner QT-185, were prepared using the recommended concentration of 1% v/v. These sanitizers were mixed with water in a polyethylene tank (Figure 1) and placed under sunlight for a week. QAC strength was evaluated on days 3, 5, and 7 using color-changing test paper similar to PH test strips. The test strip was immersed in the solution without shaking for 10 seconds, as per the provided instructions. None of the three sanitizers exhibited any signs of breakdown or degradation during these 7 days even when stored in direct sunlight under conditions in which air temperature routinely exceeded 105 F (Figure 1).
