Sanitization of soft fruits with ultraviolet (UV-C) light.

The U.S. Food and Drug Administration (FDA) Food Safety Modernization Act requires growers/packers of fresh fruits and vegetables to adapt preventive microbiological controls such as chemical sanitizers to minimize the risk of human pathogens. Tree-ripe fruits cannot withstand vigorous washing steps without impairing product quality, thus these fruits are manually packed without the use of water. To satisfy the FDA’s requirement for preventive controls and to enhance microbial safety of the soft fruits, products must be sanitized by non-aqueous technologies. Our proposed project is designed to study the feasibility of applying ultraviolet (UV-C) light to tree-ripe fruits (viz., apricots and/or peaches). Specifically, we plan to assess the efficacy of UV-C in inactivating common enteric human foodborne bacterial pathogens and maintaining fruit quality during post-UV storage. Furthermore, to ensure and validate uniform UV-C exposure of all fruit surfaces, a rotating conveyer and the use of UV film dosimetry will be evaluated. In addition, the technology will be tested in commercial trials with our industry cooperator. Successful demonstration and implementation of UV-C technology will enable the fruit industry to meet the requirements of the Food Safety Act, while improving microbial safety and increasing the consumption of healthful fresh fruits.

The Food Safety Modernization Act authorized the U.S. Food and Drug Administration (FDA) to require packers of fresh fruits and vegetables to adopt microbiological preventive control measures or provide assurances that the identified hazards are significantly minimized or prevented (UFPA 2011). Currently, the produce industry commonly uses aqueous sanitizers such as chlorine to wash fresh fruits and vegetables. Tree-ripe stone fruits and some berries, however, cannot withstand these vigorous washing steps because of their advanced maturity and fragility. Instead, the fruits are typically packed on labor-intensive hand packing lines without the use of wash water. To satisfy the FDA’s recent requirement, fruits must be sanitized by non-aqueous technologies. Ultraviolet (UV) light is a non-aqueous treatment that can destroy microorganisms. The proposed project intends to study the feasibility of applying UV-C light (254 nm) to tree-ripe fruits (apricots and/or peaches). Specifically, we plan to assess the efficacy of UV-C in inactivating human pathogens (E. coli O157:H7 and Salmonella spp.) for maintaining fruit quality and shelf-life of fruits after UV treatment. Furthermore, to analyze and ensure uniform UV-C exposure of all fruit surfaces, a rotating conveyer and the use of UV film dosimetry will be utilized. Various dose levels will be assessed in order to determine the optimum conditions necessary to inactivate human pathogens on apricots and peaches, without causing damage to the fruit. In addition, large scale trials will be conducted at our industrial collaborator’s site to study commercial feasibility. When possible, in-season fruits from Washington State will be used in the proposed study. The successful demonstration and implementation of this technology will enable the fruit industry to meet the requirements of the FDA Food Safety Act while improving the microbial safety and increasing the consumption of healthful fresh fruits. The UV technology developed in the proposed study will not only allow many grower/packers to continue marketing the tree-ripe fruits, but also will enable the fruit industry as a whole to adapt the technology to other types of fruits such as apples, pears, etc.

1. Determine the efficacy of UV-C light in inactivating E. coli and Salmonella spp. on inoculated fruit

2. Determine the survival and growth of pathogens during post-UV storage

3. Evaluate fruit shelf-life and changes in fruit quality during post-UV storage at 4 and 20°C 

4. Ensure and evaluate UV exposure uniformity using a rotating conveyor and film dosimetry

5. Conduct commercial trials to evaluate the feasibility of the UV technology; 

6. Evaluate consumer acceptance of UV technology

UV-C can be used to enhance the microbial safety of apricots with reductions of E. coli O157:H7 and Salmonella spp. on apricot fruit ranging from 1 to 2.5 log CFU/fruit without significant impact on fruit quality. The dosimetry system developed in the project may be applied by the fruit industry to assess the dose uniformity of individual fruit. E. coli ATCC 25922 may serve as a suitable surrogate for the pathogenic counterpart in validating UV-C effectiveness on the surface of apricots and, potentially, other fruits. A rotating device was developed and tested in the lab setting. Future efforts should be on scale up and application of the device in a commercial facility to achieve a higher reduction of pathogens. The UV-C system should be used in conjunction with other good manufacturing practices and good agricultural practices to be optimized in order to enhance microbial safety of soft fruits. Consumer acceptance of UV-C technology for produce appears to be similar, or in some cases, better than currently used food processing technologies for produce and other food items. The term “ultraviolet light” was the most preferred term to refer to UV-C treatment of produce. The implementation of this technology will enable the fruit industry to improve the microbial safety and increasing the consumption of healthful fresh fruits. The UV technology developed in the proposed study will not only allow many grower/packers to continue marketing the tree-ripe apricots, but also will enable the fruit industry as a whole to adapt the technology to other types of fruits such as apples.