Throughout the various phases of the food production and processing system, opportunities for contamination exist. Reliable laboratory and field methods are necessary to rapidly detect and trace the source of contamination. To enhance early detection and continuous monitoring of foodborne disease nationwide, new and improved diagnostic tools are needed. They should provide rapid, cost-effective testing for pathogens in food animals, agriculture and aquaculture products, animal feeds and processed food products.
One new tool is called the Food Sentinel System (FSS). Unlike other systems that involve the collection of a sample at a given time and place and subsequent sample preparation and analysis, the Food Sentinel System remains with the product and performs a continuous tracking for product safety. This helps alert food processors, distributors, public health officials and consumers of the presence of pathogenic bacteria of human health concern in fish, poultry, meat and some liquid products.
The Food Sentinel System is based on a solid-phase immunobead assay (SPIA) and antibody sandwich principles modified to allow the continuous flow and exposure of product juices and contaminating microorganisms. It is an immunochemical method linked to a uniquely designed commercial universal product code (UPC) bar system.
As contaminants such as Salmonella sp., Escherichia coli 0157:H7, Listeria monocytogenes flow through the FSS, they bind to colored immunobeads (specific-pathogen antibodies bound to black latex microspheres) that, in turn, migrate to be captured by a second specific antibody. This antibody is attached to a membrane forming part of the bar code system. The presence of the contaminating bacteria is evident by the formation of a localized dark bar on the membrane as a result of the immunobeadantigen complex agglutinating on the capture antibody location.
The dark bar modifies the appearance of the overlying bar codes in two ways. The purveyor’s bar code is rendered unreadable by any scanner, while the lower FSS bar code indicating contamination becomes readable from the added bar. The membranes are designed to allow entry of pathogenic bacteria, prevent entrance of interfering substances and maintain the immunobead-bacteria complex inside the system.
Bar code scanning can be done with hand-held devices or be automated as part of packaging, transportation, storage and retail operations. Scanners can be programmed to read the type of contamination, product and the date and location of the reading. In the absence of scanning devices, the consumer at home can observe the appearance of a new symbol on the bar code signaling contamination.
The Food Sentinel System is inexpensive. Its usefulness in the food industry is greater than conventional microbial testing because it continuously monitors microbial presence from slaughter to the processing plant to the consumer. Product and economic losses are, therefore, reduced. Its universal presence is better than conventional monitoring by random sampling.
Research at the LSU Agricultural Center’s Department of Food Science will help bring the Food Sentinel System into actual use, which is expected in the next few years. Contributions of LSU AgCenter research include the following:
- Concept and adaptation of S-PIA to the optical scanning bar code system.
- Evaluation and selection of system solutions.
- Selection of membranes, latex beads, structural films and surfaces, absorbent pads and filters.
- Evaluation and optimization of the migration process for optimal flow.
- Simplification and reduction of system dimensions.
- Testing under natural packaging conditions. Testing under diverse physical conditions.
- Testing additional structural materials.
The Food Sentinel System is a registered trademark of SIRA Technologies, which helped with the funding of this research.
(This article was published in the spring 2000 issue of Louisiana Agriculture.)