Micro-fluidic mixer and method of determining pathogen inactivation via antimicrobial solutions
Inventors
Luo, Yaguang • ZHANG, BOCE • Millner, Patricia D.
Assignees
University of Maryland Baltimore • US Department of Agriculture USDA
Publication Number
US-10233482-B2
Publication Date
2019-03-19
Expiration Date
2035-09-09
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Abstract
A sample of produce wash water containing an antimicrobial sanitizer fluid, and a reference pathogen fluid are both injected into a pathogen inactivation region of a micro-fluidic mixer. The produce wash water (i.e. sanitizer fluid/pathogen fluid mix) is directed through mixer elements in the pathogen inactivation region of the micro-fluidic mixer. In the sanitizer deactivation region, a sanitizer deactivation solution is added to the sanitizer fluid/pathogen fluid mix to produce a deactivated solution. The deactivated solution is evaluated for the presence of the pathogen and the characteristics of the sanitizer. In the preferred embodiment, the sanitizer comprises chlorine and the pathogen comprises E. coli bacteria.
Core Innovation
The invention disclosed is a micro-fluidic sanitizer analysis system and method specifically designed to determine pathogen inactivation kinetics in a solution, particularly for assessing the sufficiency of free chlorine in produce wash water to inactivate target pathogens such as E. coli O157:H7. The system comprises a micro-fluidic mixer with distinct pathogen inactivation and sanitizer deactivation regions. In this device, a sanitizer fluid mixes with a reference pathogen fluid in the pathogen inactivation region to allow interaction and partial or complete pathogen inactivation. Subsequently, the sanitizer is inactivated in the sanitizer deactivation region by introducing a dechlorinating solution to produce a deactivated sanitizer fluid, which is then analyzed for pathogen presence and sanitizer characteristics.
The problem addressed by this invention arises from the challenge in the fresh produce industry of maintaining adequate sanitizer levels, primarily free chlorine, in wash water due to its rapid consumption by reaction with organic matter. There is a critical need for precise and fast determination of free chlorine concentration and contact time required to inactivate pathogens effectively, particularly with kinetics at under 1 second. Prior methods could not adequately measure these very rapid responses. The invention overcomes this by utilizing a micro-fluidic mixer capable of controlling contact times as brief as 0.1 second, enabling high precision in studying the interaction and inactivation kinetics.
The micro-fluidic mixer is constructed with multiple inlets for bacterial suspension, chlorine sanitizer solution, and a sanitizer deactivation fluid, organized into mixing regions including Y-injection mixers and Dean's vortex mixers incorporating chaotic mixer elements to enhance turbulent mixing within the laminar flow regime. Flow rates are adjustable to precisely control contact time. The device is fabricated using known microfabrication techniques and allows for the collection of effluent for analysis to determine surviving pathogen quantities and sanitizer properties. The system provides a novel means to evaluate and optimize sanitizer concentrations and contact times to prevent pathogen survival and cross-contamination during produce washing.
Claims Coverage
The patent includes one independent claim defining a micro-fluidic sanitizer analysis system with specific channel and mixing configurations, incorporating a sanitizer inactivation step following pathogen inactivation mixing.
Micro-fluidic sanitizer analysis system with integrated pathogen inactivation and sanitizer deactivation channels
A pathogen inactivation channel comprising a first Y-injection mixer with two inlets and sequential S-shaped serpentine channels with chaotic mixer elements, connected in series to mix produce wash and bacterial solution, connected to a sanitizer deactivation channel that includes a second Y-injection mixer and further S-shaped serpentine channels with chaotic mixer elements, allowing mixing with a sanitizer deactivating solution before effluent collection for analysis.
Continuous fluid communication configuration
The system is structured to ensure fluid communication and serial connection between the first injection mixer, serpentine pathogen inactivation channels, second Y-injection mixer, and serpentine sanitizer deactivation channels.
Incorporation of Dean's mixer within pathogen inactivation channel
The pathogen inactivation channel includes at least one Dean's mixer to enhance fluid mixing efficiency.
Use of chlorine produce wash solution as produce wash sample
The system is configured to process produce wash solutions containing chlorine.
Employment of E. coli as the reference bacterial solution
The reference bacterial solution introduced into the system comprises E. coli.
Equivalent structure of pathogen inactivation and sanitizer deactivation channels
The system maintains a continuous fluid channel where the pathogen inactivation channel has the same structural configuration as the sanitizer deactivation channel.
The claims define a micro-fluidic system comprising sequential mixing channels with chaotic mixer elements and Y-injection mixers arranged to sequentially mix a produce wash sample with a bacterial reference solution and then with a sanitizer deactivation solution, enabling effective pathogen inactivation assessment and subsequent sanitizer inactivation for analysis.
Stated Advantages
Provides a quick and accurate means of determining free chlorine adequacy for pathogen inactivation with contact times as short as 0.1 second.
Allows precise control and measurement of sanitizer-pathogen interaction time by adjusting solution flow rates.
Efficient and rapid mixing of fluids under laminar flow conditions is achieved using chaotic mixer elements and Dean's vortex mixers.
Enables determination of chlorine concentration-contact time relationships critical for preventing pathogen survival and cross-contamination.
Offers critical empirical data for food safety regulation development and facilitates optimization of produce washing sanitization processes.
Documented Applications
Determination of whether sufficient free chlorine is present in a produce wash solution to inactivate E. coli O157:H7 pathogens.
Studying pathogen inactivation kinetics at time scales below one second during fresh produce washing.
Evaluation of sanitizer concentration and exposure time to prevent pathogen survival and cross-contamination in produce processing.
Use in produce processing industry for optimizing wash water sanitization to ensure food safety.
Empirical testing and validation of chlorine disinfection models for bacterial inactivation.
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