Acrylamide and Chips: LC-MS Monitoring Maillard Reaction in Starchy Food

One of the major by products of the Maillard browning reaction, where reduced sugars interact with the amino acid asparagine under conditions of high heat and low moisture, is acrylamide. The IARC (International Agency for Research on Cancer) classifies this compound, a hydrophilic, polar molecule with low volatility and low molecular weight, as a potential carcinogen, neurotoxin and DNA mutagen. However, although recognized as present in certain foods, the food industry currently has placed no upper limits on its presence in its products. The European Commission for example, issues only indicative amounts to illustrate average concentrations commonly encountered in processed ingredients.

One reason for the lack of limits may be that acrylamide is difficult to analyze successfully and easily. The foods where it occurs are complicated matrices for analysis and frequently confuse results. Ferrer-Aguirre and co-authors (2015) present a simple and straightforward method for sample preparation, cleanup and analysis in two foods, potato chips and grilled asparagus, known to contain acrylamide.

Ferrer-Aguirre et al. base the new analytical method around high performance liquid chromatography coupled with tandem mass spectrometry using a triple quadrupole (HPLC-QqQ-MS/MS)¹. First, the researchers prepared the food samples by crushing and homogenizing them. They then spiked the blank samples (fresh asparagus, raw potato) using stock solutions of commercial acrylamide standards.

To extract analytes from the food matrices, Ferrer-Aguirre et al. used a solid-liquid extraction (SLE) process with water as the solvent. They followed this with solid phase extraction (SPE) or dispersed (d)-SPE as a clean-up to prevent matrix effects confusing subsequent mass spectrometric analysis. As the researchers optimized this sample preparation process, they found that (d)-SPE worked most effectively for asparagus, whereas SPE clean-up was sufficient for preparing potato samples.

Prior to examining food matrices, the researchers examined acrylamide chromatographic data using HPLC-QqQ-MS/MS to calibrate the workflow. In addition, the team also compared different analytical columns used in conjunction with mass spectrometry, finding that the Thermo Scientific ODS hypersil column performed best. The analytical workflow established showed limits of detection and quantitation (LOD, LOQ) of 4 and 12 µg/kg for chips, and 2 and 5µg/kg for asparagus. They achieved recoveries of 90-117% for chips and 90-116% for asparagus in the assays.

Following validation of the methodology, the team turned to examining food samples, potato chips and grilled asparagus, by HPLC-QqQ-MS/MS. They measured acrylamide levels ranging between 105 and 860 μg/kg in potato chips, and from 292 to 1469 μg/kg in grilled asparagus.

As a further step, Ferrer-Aguirre and co-authors also looked to see if acrylamide metabolites were detectable in urine after ingestion. They collected samples from human volunteers at 12, 24 and 48 hours after they had eaten 100g of grilled asparagus. The team could identify acrylamide-N-acetylS-(2-carbamoylethyl)-L-cysteine (AAMA) by ultra-high performance liquid chromatography coupled with Orbitrap mass spectrometry (Q Exactive Orbitrap mass spectrometer – Thermo Scientific). In one subject, this was identifiable at 12 hours post-ingestion.

In their conclusion, Ferrer-Aguirre et al. state that HPLC-QqQ-MS/MS analysis following SLE water extraction and (d-)SPE cleanup is not only simple, rapid and cheap, but it is also an effective method for determining acrylamide content in potato chips and grilled asparagus.

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Reference

1. Ferrer-Aguirre, A. et al. “Simple and Fast Determination of Acrylamide and Metabolites in Potato Chips and Grilled Asparagus by Liquid Chromatography Coupled to Mass Spectrometry“, Food Analytical Methods DOI 10.1007/s12161-015-0304-6