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Grain Residue Analysis and Levels of Detection

Like any analysis, grain residue analysis has certain limitations that will determine the level of detection possible.

levels of detection in grain residue analysisIn general, residue monitoring endeavours to:

  • Quantify the presence or absence of potential contaminants or residues
  • Verify that residues in products are below maximum residue limits
  • Deliver alerts if limits are exceeded so that corrective action can be taken.

Consumers demand that their food be safe and clean. Meeting this demand requires careful surveillance for potential contaminants and residues.

Symbio Laboratories is a key provider of testing under the National Residue Survey (NRS) grain residues program. This screening covers pesticide residues, heavy metals and mycotoxins over an ever-increasing suite of compounds. Any detection is treated seriously, as the consequences to producers, exports and consumers may be significant.

Detectable Levels vs Reportable Levels

This raises the important issue of detectable levels versus reportable levels for the many contaminants listed and the consumer’s perception that food should be “free” of all contaminants.

The assumption has traditionally been “if residues are not detected, then they are absent”; however, in reality, this is not always true, with there being no such number as “0” in residue chemistry!

As technology and equipment improve, more sensitive techniques are employed that are capable of detecting residues to sub-parts per trillion.

Limit of Reporting (LOR)

Industry terminology defines the Limit of Reporting (LOR) as the minimum concentration of a residue used for reporting purposes and the LOR is usually one-hundredth of the respective Maximum Residue Limit (MRL). Typically, results of analyses lower than the LOR are not included in a report; so the MRL can be defined as the maximum concentration of a residue which is legally permitted or recognised as acceptable in or on a food, an agricultural commodity or animal feed.

It is against the MRL that the final product is tested for compliance. Of concern are those chemicals for which there is no MRL set. In this instance, any detectable level of that chemical in those products would constitute a violation of the food standards code. As Detection Limits (DLs) are the estimate of concentrations (where we are fairly certain that the compound is present), any concentration below this limit may not be detected and concentrations above this limit are almost certainly detected.

This brings into question at what point is a chemical “detectable”, what influences this detection limit and how you can minimise the risk?

The Future of Grain Residue Testing

Into the future the levels of detection for metals, organic and inorganic compounds will continue to decline, additionally, the scope of compounds being routinely monitored by regulators and international markets will increase. To overcome this, modern commercial laboratories invest heavily in equipment that allows for the screening of multiple analytes in a single analysis, this provides for high sensitivity, low reporting limits and rapid turnaround in results.

Implementing and maintaining a robust food safety plan that identifies the potential source of contamination for all inputs is highly recommended. This plan should identify preferred suppliers that maintain strict quality programs and vendor declarations. In addition, careful sampling and retention of samples of inputs together with periodic surveillance for known contaminants is essential.

Targeted heavy metal testing, residue testing of mineral sources, testing of imported inputs and novel additives is also recommended. This should be combined with the periodic benchmarking of the residue status of the crop.

Contamination from over spraying is becoming increasingly common and generates the urgent need for testing of the standing crop to quantify its residue status.

Symbio Laboratories are NATA accredited, their equipment utilises the latest technology and they have specialist industry experienced experts to assist customers with their testing needs.



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