Innovations in ultraviolet-C technologies for fresh produce growers to reduce human pathogens in agricultural surface water and on fresh produce surfaces

Abstract

Ultraviolet-C (UV-C) irradiation is well-known for its high antimicrobial efficacy and low environmental toxicity compared to its chemical sanitizer counterparts. Although UV-C is well implemented in various food industries, the technology has yet to become popularized in the fresh produce industry. The purpose of this work was to generate knowledge and understanding towards innovations in UV-C technologies for use in the fresh produce industry. The prevalence of generic E. coli in agricultural water samples (N= 426) from Kansas and Missouri was first assessed to determine their potential microbial risk. While there were no statistically significant differences detected between the two states (P < 0.4023), the average concentration of generic E. coli in surface water sources (158.7 most probable number [MPN]/100 mL; n= 247) was greater than that of ground water sources (20.4 MPN/100 mL, n= 179; P < 0.0001). These results indicate a need for safe, environmentally friendly agricultural water treatment options for fresh produce growers in the region. As agricultural surface waters were shown to carry a significantly higher microbial risk than ground waters, a follow-up study was performed to test the efficacy of two UV-C devices to reduce generic E. coli populations in three on-farm agricultural surface water sources. A generalized additive model was used to determine the effect of water characteristics, flow rate, and UV-C device on the antimicrobial efficacy of a low power, low flow (1-9 gallons per minute (GPM), 1.34-gallon capacity) and a high powered, high flow (1-110 GPM, 4.75-gallon capacity) UV-C device at flow rates of 6, 7, and 9 GPM. From this data, an online tool was developed for growers to calculate the predicted efficacy of the devices to treat their agricultural water source. A survey was then designed to explore the low adoption rate of UV-C devices by the Kansas and Missouri fresh produce growing community. The survey instrument measured grower knowledge of UV-C, their attitudes towards UV-C technology, and included a needs assessment to support the on-farm implementation of UV-C. There was a large variation in grower knowledge of UV-C (N=82) and stepwise regression (n= 62) revealed that overall attitudes were most influenced by grower knowledge of UV-C (P<0.0001), farm size (P=0.0199), farm income (P=0.1047), and state (P=0.1237). Overall, the responses indicate that there is an unmet need for more information regarding the benefits, costs, implementation strategies, and technical skills regarding UV-C devices for agricultural water treatment. Further on-farm applications were investigated, notably, a UV-C treatment chamber fitted with UV-Light Emitting Diodes (LEDs) on all sides to provide simultaneous treatment of an entire fruit surface. A maximum 0.95-log reduction of generic E. coli was detected after 60 s of treatment in blueberries. After optimizing the chamber for improved thermoregulation and UV-C intensity, the chamber achieved a 1.48-log reduction of generic E. coli after 60s in fresh strawberries, indicating the technology’s suitability for treating diverse fruits. Future study should focus on scaling this technology to fit the needs of the fresh produce industry. In summary, these studies provide future research directions for on-farm UV-C innovations to improve produce safety. The studies demonstrate that there is a need for safe, effective, non-chemical agricultural water treatment methods – a niche that UV-C devices can be successfully fill. Yet there continues to be a knowledge gap that needs to be addressed to increase the produce grower adoption rate of on-farm UV-C devices. The fresh produce industry could also benefit from innovations in UV-C for whole-fruit treatment, but more research is needed to increase the scale of this technology to treat more fruits simultaneously.