Most DNA testing in quality assurance still works one question at a time: is species X in this sample? For a single-ingredient product, that is often enough. For a blended botanical, a processed meat product or a mixed seafood item, it is not, because the question you actually need answered is “what is in here?”
The one-question-at-a-time problem
Conventional PCR detects a small number of targets per reaction. To check a product for several possible species, a lab runs several reactions, each designed around a species it already suspects. That has two costs.
- Time and consumables grow with every species you add. A ten-ingredient formulation, plus the usual substitutes for each ingredient, quickly becomes a stack of plates.
- You only find what you thought to look for. If a supplier has substituted a species nobody suspected, a targeted test for the expected species will not raise it.
What a microarray does differently
A DNA microarray is a glass slide carrying many short DNA probes, each designed to match a stretch of DNA from a particular species. DNA extracted from the sample is labelled and applied to the slide. Wherever the sample contains matching DNA, it binds to the probes and gives a signal that the scanner records.
Because every probe is read in the same run, one slide can screen a sample against a whole reference panel at once: the species that belong in the product, the common substitutes, and the known adulterants for that product class. Each QAID microarray product carries a panel designed for its own quality-assurance challenge, such as botanicals for Botanical-ID or spoilage organisms for Spoilage-ID.
Why that changes the question
A multi-target run turns “is the right species present?” into “which of the species on this panel are present?” In practice that means:
- Undeclared species show up without a special request. Fillers and substitutes on the panel are screened every time, not only when someone suspects them.
- Multi-ingredient products are checked in one test. A formulation is screened for each of its declared ingredients in a single run.
- Results are comparable across lots. Every sample is read against the same panel, so a change between batches stands out.
One limit is worth stating plainly: a microarray detects the species its panel was designed for. That is why QAID panels are curated per product class and grow as new substitution risks are identified.
Processed materials
Powdered, milled and processed plant material is where macroscopic and chromatographic identity tests are often inconclusive. DNA-based identification can still work on these materials. How much usable DNA survives depends on processing and extraction, so suitability is confirmed for each material type with a DNA quantity test before results are relied on.
Where PCR still fits
A microarray does not make PCR obsolete. Targeted PCR remains a good tool for a single, well-defined question, and confirmatory methods remain essential where regulations require them. For example, Microbe-ID is an early-warning screen that tells a lab where to focus confirmatory pathogen testing; it complements those tests and does not replace them. The strength of the microarray is breadth: one run gives a wide view of a sample, so the targeted work that follows is aimed in the right place.
Bringing it into your lab
QAID supplies the microarray products, the QAID App to analyze the results, and the training to implement both in your own laboratory. If you are weighing a microarray workflow against your current test stack, tell us about your products and QA goals and we will help you work out where it fits.