Acrylamide Detection Now Quicker And Cheaper With Near-Infrared Spectroscopy

♦ Acrylamide is a potent carcinogen and neurotoxin formed in overcooked foods

♦ Near-infrared spectroscopy (NIRS) used to measure acrylamide levels in fried foods.

♦ NIRS cheaper and easier to use than current methods of analysis

Acrylamide is a potent carcinogen and neurotoxin formed in fried and baked foods after cooking at high temperatures. The biggest concern is with stuffs such as fried chips or fries where potatoes are taken beyond the stage of being golden-brown to being overcooked. Proteins reacting with certain carbohydrates in the potato are converted to acrylamide at frying temperatures. Acrylamide detection and secure measurement in cooked foods currently relies on gas chromatography (GC) and high-pressure liquid chromatography (HPLC) which are time consuming. Another technique using NIRS is being devised to make measurement more secure, cheaper and easier to conduct.

The Food Safety Authority (FSA) has issued general guidelines to reduce cooking temperatures and ‘Go for Gold’ in a bid to reduce the acrylamide content we are exposed to in our cooked foods. The main concern is the reaction between free asparagine and reducing sugars such as glucose at temperatures above 120°C via the Maillard browning reaction (Mottram et al., 2002; Zyzak et al., 2003). Boiling does not produce this molecule.

The first measurements of acrylamide in food appear in reports on amino-acid analysis when various cooked foods were subjected to isotope dilution liquid chromatography using tandem mass spectrometry detection (LC-MS/MS) (Rosen and Hellenas, 2002). This initial analysis coincided in part with the first announcement by Stockholm University and the National Food Administration (Agency) in Sweden, on April 24^th, 2002.  They unequivocally showed that acrylamide formation was not an artefact in food formation.

Subsequently, GC-MS (gas chromatography-mass spectrometry) and LC-MS/MS studies were refined and developed to accurately estimate the levels of the carcinogen in a variety of foods. Here, acrylamide was brominated for an improved GC-MS method whilst a new technique for the unchanged molecule was developed using LC-MS/MS (Tareke et al., 2002). Bromination incidentally increases the volatility of acrylamide making it easier to separate from its matrix.

Over a number of years, GC and LC methods have been coupled to a host of different detectors. We have seen biosensors, enzymatic analysis amongst various bioanalytical techniques too. Many of these are now reviewed and put into context (Oracz et al., 2011; Tekkeli et al., 2012; Elbashir et al., 2014; Hu et al., 2015).

One of the key considerations is extraction of acrylamide from what is a highly complex and diverse matrix. Solid-phase micro-extraction is effective and well established (Lee et al., 2007). This did not need derivatization to release the molecule and could be analysed using GC with positive chemical ionization tandem mass spectrometry. Where acrylamide detection is required below 30 ng/g, then GC-MS with derivatization is preferred (Liu et al., 2008). The best sensitivity for acrylamide has been to adopt chromatography (Tekkeli et al., 2012) often with derivatization using xanthydrol  (Yamazaki et al., 2012; Lim and Shin, 2013). The main issue is the cost and time needed for measurement of a chemical which demands rapid analysis and turnaround.

To current matters now, researchers in the Food Science Research Unit (FSRU) at the US Dept. of Agricultural Research Service (USDA ARS) in Raleigh, North Carolina led by Suzanne Johanningsmeier have just released methodologies using NIRS which make detection and analysis easier and cheaper. They initially looked at spiked samples of potato flour to establish the accuracy and veracity of the method. Then, their test material was French Fries produced using different pretreatments and cooking times. Samples of fries were also taken from various restaurants. A model relating output from NIRS to the acrylamide content in fries demonstrated the methods success. A comparison between the cost of the current standard methods shows analysis is $250 per sample versus $25 per sample using NIRS. The considerable mark-down in costs should ensure wider uptake of the methodology, especially by those such as potato growers and food processors relying on frying. The implication might be to select potato cultivars or crops with low asparagine levels for example so that acrylamide formation is reduced (USDA, 2016).

References

Elbashir, A. A., Omar, M. M. A., Ibrahim, W. A. W., Schmitz, O. J., & Aboul-Enein, H. Y. (2014). Acrylamide analysis in food by liquid chromatographic and gas chromatographic methods. Crit. Rev. Anal. Chem., 44(2), pp. 107-141

Hu, Q., Xu, X., Fu, Y., & Li, Y. (2015). Rapid methods for detecting acrylamide in thermally processed foods: A review. Food Control, 56, pp. 135-146

Lee, M. R., Chang, L. Y., & Dou, J. (2007). Determination of acrylamide in food by solid-phase microextraction coupled to gas chromatography–positive chemical ionization tandem mass spectrometry. Analytica Chimica Acta, 582(1), pp. 19-23

Lim, H. H., & Shin, H. S. (2013). Ultra trace level determinations of acrylamide in surface and drinking water by GC–MS after derivatization with xanthydrol. J. Separation Science, 36(18), pp. 3059-3066

Liu, J., Zhao, G., Yuan, Y., Chen, F., & Hu, X. (2008). Quantitative analysis of acrylamide in tea by liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Food Chem., 108(2), pp. 760-767

Mottram, D. S., Wedzicha, B. L., & Dodson, A. T. (2002). Food chemistry: acrylamide is formed in the Maillard reaction. Nature 419(6906), pp. 448-449

Oracz, J., Nebesny, E., & Żyżelewicz, D. (2011). New trends in quantification of acrylamide in food products. Talanta, 86, pp. 23-34

Rosén, J., & Hellenäs, K. E. (2002). Analysis of acrylamide in cooked foods by liquid chromatography tandem mass spectrometry. Analyst 127(7), pp. 880-882

Tareke, E., Rydberg, P., Karlsson, P., Eriksson, S., & Törnqvist, M. (2002). Analysis of acrylamide, a carcinogen formed in heated foodstuffs. J. Agric Food Chem, 50(17), pp. 4998-5006

Tekkeli, S. E. K., Önal, C., & Önal, A. (2012) A review of current methods for the determination of acrylamide in food products. Food Analytical Methods 5(1), pp. 29-39

Yamazaki, K., Isagawa, S., Kibune, N., & Urushiyama, T. (2012). A method for the determination of acrylamide in a broad variety of processed foods by GC–MS using xanthydrol derivatization. Food Additives & Contaminants: Part A 29(5), pp. 705-715

USDA (2016) A Quicker Way To Detect Acrylamide in French Fries. AgResearch Magazine. November edt. https://agresearchmag.ars.usda.gov/2016/nov/frenchfries/

Zyzak, D.V., Sanders, R.A., Stojanovic, M., Tallmadge, D.H., Eberhart, B.L., Ewald, D.K., Gruber, D.C., Morsch, T.R., Strothers, M.A., Rizzi, G.P. and Villagran, M.D., (2003) Acrylamide formation mechanism in heated foods. J. Agric Food Chem. 51(16), pp.4782-4787.