Advancing the food safety arms race

The merits of biochip array technology; a study in honey analysis. By Gary Smith

As the food industry is developing globally the methods used to safeguard the supply chain must also move forward. This, in part, requires industry laboratories and testing facilities to have access to reliable analysis for drug residues and antibiotics, which are essential to the production process. Food industry scientists, government officials and local producers are regularly on the lookout for the latest and most effective measures to secure global food chains. Development in this area is becoming increasingly crucial and the food safety ‘arms race’ is definitely under way with millions being spent on investment into new technology. Biochip array technology (BAT) from Randox Food Diagnostics, a leader in honey analysis, is generating demand from various sectors of food producers.

Backed by extensive research and over £200m of investment, BAT is making testing simple by providing results for multiple analytes from a single sample. The multiplex screening of drug residues is done on a 9x9mm biochip presenting different test sites in discrete test regions (DTRs) defining arrays of miniaturised immunoassays. To put this into perspective, by using only one 9x9mm biochip, which can contain up to 22 tests, there is no need to use the same number of individual standard ELISA test kits.

The technology in action

One industry that has benefitted from BAT is the honey sector. Ensuring that honey isn’t adulterated and is free from antibiotics is a key part of any quality assurance programme. In terms of the mass testing of honey, processors require a system that can ensure the continued confidence of their customers.

Some of the world’s biggest processors have implemented BAT to ensure accurate detection of drug residues as it offers an impressive false positive rate of <5%, and the importance of accuracy in the laboratory cannot be overstated.

Example of application

5-Nitroimidazoles are increasingly used to prevent and control outbreaks of Nosema apis, which reduces the life span of carrier bees in hive populations. This affects the productivity of the hive, having a negative impact on the production of honey. 5-Nitroimidazoles have been noted to have carcinogenetic properties.

Other antibiotics with potential carcinogenetic properties, such as chloramphenicol, can be found in adulterated honey as it is used to treat foulbrood, which can destroy a hive’s bee population.

These drugs are not authorised for the treatment of honeybees in the EU. However, they are authorised in other countries, which could raise problems with honey imports and consumer protection. BAT’s multi-analytical screening approach has been used in this study to evaluate its application to the simultaneous detection of a broad range of nitroimidazoles, chloramphenicol and chloramphenicol glucuronide from a single sample.

Methodology and results

A biochip array kit (Antimicrobial Array V) and the Evidence Investigator from Randox Food Diagnostics were used. Simultaneous competitive chemiluminescent immunoassays were employed. Before application to the biochip, honey samples were prepared using a simple solvent extraction method.

Results from the analysis of honey samples showed a broad specificity profile for nitroimidazoles as indicated by the cross-reactivity values (Fig. 1). The assay standardised to chloramphenicol also detected chloramphenicol glucuronide (Fig. 2).

Limits of detection for this study were stated as 0.9ppb for metronidazole and 0.1ppb for chloramphenicol.

While this particular study shows capability in the honey industry, BAT is also applicable to the multiplex screening of other drug residues in other matrices and companies in the meat, seafood, dairy and mycotoxin testing markets are routinely using it as an essential aspect of their quality assurance programmes. This showcases not only the performance of the technology, but also the versatility which represents a leap forward in terms of the future of drug residue screening in the international food industry. 

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Gary Smith is with Randox

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