Acrylamide is a nasty molecule. It is a neurotoxin, genotoxin and carcinogen which makes it highly undesirable especially when it forms in food. Hogervorst et al., (2007, 2008) found an association between acrylamide in the diet and an increased risk of endometrial, ovarian and kidney cancer.
The issue has largely made food scientists and chefs alike think seriously about how to cook food without creating this molecule. The whole issue came to light when acrylamide was found in fried foods and oven-cooked foods, especially those that were protein and thus relatively nitrogen rich (Rosen & Hellenas, 2002; Tareke et al., 2002).
Frying And Acrylamide Formation
Potatoes are especially prone to acrylamide formation during frying. The compound forms very early on in the Maillard reaction when the amino acid asparagine reacts with reducing sugars such as glucose and fructose, usually at temperatures above 120 °C as in the cooking processes of frying and baking (Friedman, 2003; Yaylayan et al., 2003).
Asparagine is a major dietary amino acid. It is prevalent in potatoes as well as cereals.
Processing parameters need to be examined when frying potatoes for whatever purpose. One study, (Taubert et al., 2004) investigated various factors in acrylamide formation when frying potatoes. These were the impact of temperature, heating time, browning level, and surface-to-volume ratio (SVR).
If the potatoes had a low SVR, then the acrylamide content increased with increasing processing times and temperatures. However, if the SVR was medium to high then the maximum acrylamide was formed between 160−180 °C. Most interestingly, with higher frying temperatures or prolonged processing produced a reduction in acrylamide levels. They did not find browning was a ‘reliable measure’ of acrylamide content in the large-surface potato pieces.
Researchers at the Institute of Food Engineering for Development in the Univ. Politècnica de València, have examined new cooking methods that would allow us to enjoy the great colour and flavour of such foods (Sansano et al., 2015). One in particular, air-frying looks highly promising especially if used in combination with pretreatments. In this study they took a variety of potato called Frisia which is available virtually all year in Spain. These potatoes were prepared by washing and peeling, and then cutting into 7 mm thick slices before coring to produce discs for analysis.
They took potatoes from two different time periods in March-April and May-June to understand how the reducing sugars at different times of the year affected acrylamide formation. The amount of acrylamide is dependent on the concentration of both the amino-acids and the levels of reducing sugars. Another quality parameter, colour was also checked.
The potatoes were pretreated with a range of chemical solutions:- citric acid, glycine, calcium lactate, sodium chloride, or nicotinic acid [vitamin B3]. They air-fried the potato samples and checked how much acrylamide was generated and compared it with the oil-based frying method as a control and reference.
They used the browning colours of the potato crust as a measure of the rate of Maillard browning and found it decreased as the initial reducing sugars level increased in the starting material. Irrespective of any pretreatments, Maillard browning rates were higher for air-frying than oil frying. The researchers found that air-frying reduced acrylamide content by about 90% compared with conventional deep-oil-frying without a pretreatment being necessary. What was notable, was that deep-oil fried potatoes pretreated with solutions of nicotinic acid, citric acid, glycine at 1%, and NaCl at 2% produced much lower acrylamide levels (a 80–90% reduction) than non-pretreated samples.
The pretreatments probably operated by reducing the reaction of the reducing sugars with asparagine. For example, glycine and nicotinic acid could easily compete with asparagine in the reaction. It is also possible that any formed acrylamide is then mopped up by covalent binding through a Michael type addition reaction (Mestdagh et al., 2008a, 2008b). No doubt other methods that remove asparagine might be possible including the use of enzymes such as asparaginase or the use of edible coatings which are claimed to have similar benefits to the pretreatments.
It would appear that air frying is a better technology for obtaining fried products and that pretreatment is important for reducing acrylamide levels if oil frying is pursued.
The Use Of Pulsed Electric Fields In Reducing Acrylamide Content
Pulsed electric fields (PEF) are applied to a range of foods as part of a non-thermal pasteurisation or processing step (Genovese et al., 2019). Research from the University of Bologna in Italy suggests some useful benefits in dealing with acrylamide. There is some evidence that PEF can be applied to the reduction of acrylamide in potato crisps. The level of reduction is claimed to be up to 30% which is substantial.
References
Friedman, M. (2003). Chemistry, biochemistry, and safety of acrylamide. A review. Journal of Agricultural and Food Chemistry, 51, pp. 4504–4526
Genovese, J., Tappi, S., Luo, W., Tylewicz, U., Marzocchi, S., Marziali, S., … & Rocculi, P. (2019). Important factors to consider for acrylamide mitigation in potato crisps using pulsed electric fields. Innovative Food Science & Emerging Technologies, 55, pp. 18-26 (Article).
Hogervorst, J.G., Schouten, L.J., Konings, E.J., Goldbohm,R.A., van den Brandt, P.A. (2007). A prospective study of dietary acrylamide intake and the risk of endometrial, ovarian, and breast cancer. Cancer Epid. Biol. Prev. 16 pp. 2304–13.
Hogervorst, J.G., Schouten, L.J., Konings, E.J., Goldbohm, R.A., van den Brandt, P.A. (2008). Dietary acrylamide intake and the risk of renal cell, bladder, and prostate cancer. Am. J. Clin. Nutr. 87 pp. 1428–38
Mestdagh, F., De Wilde, T., Fraselle, S., Govaert, Y., Ooghe, W., Degroodt, J.M., Verhé, R., Van Peteghem, C., De Meulenaer, B. (2008a) Optimization of the blanching process to reduce acrylamide in fried potatoes. LWT Food Sci. Technol. 41 pp. 1648–54.
Mestdagh, F., Maertens, J., Cucu, K., Delporte, T., Van Peteghem, C., De Meulenaer, B. (2008b) Impact of additives to lower the formation of acrylamide in a potato model system through pH reduction and other mechanisms. Food Chem. 107(1) pp. 26–31
Palazoğlu, T. K., Savran, D., & Gökmen, V. (2010). Effect of cooking method (baking compared with frying) on acrylamide level of potato chips. Journal of Food Science, 75(1), E25-E29.
Pedreschi, F., Kaack, K., & Granby, K. (2004). Reduction of acrylamide formation in potato slices during frying. LWT-Food Science and Technology, 37(6), pp. 679-685 (Article)
Rosen, J., & Hellenas, K. E. (2002). Analysis ofacrylamide in cooked foods by liquid chromatography tandem mass spectrometry. Analyst, 127, pp. 880–882
Sansano, M., Juan-Borrás, M., Escriche, I., Andrés, A. and Heredia, A. (2015), Effect of Pretreatments and Air-Frying, a Novel Technology, on Acrylamide Generation in Fried Potatoes. J. Food Sci., 80: T1120–T1128. http://doi: 10.1111/1750-3841.12843
Tareke, E., Rydberg, P., Karlsson, P., Eriksson, S., & Tornqvist, M. (2002). Analysis ofacrylamide, a carcinogen formed in heated foodstuffs. Journal of Agricultural and Food Chemistry, 50, pp. 4998–5006
Taubert, D., Harlfinger, S., Henkes, L., Berkels, R., & Schömig, E. (2004). Influence of processing parameters on acrylamide formation during frying of potatoes. Journal of Agricultural And Food Chemistry, 52(9), pp. 2735-2739 (Article).
Yaylayan, V.A., Winorowski, A., Perez Locas, C. (2003) Why asparagine needs carbohydrates to generate acrylamide. J. Agric. Food Chem. 51 pp. 1753–57.
1st revision.. Addition of new material associated with PEF and some additional notes about acrylamide.
I heard that the spokesman for Rothamsted Research UK was suggesting new guidelines were coming in this April about acrylamide in foods generally. They do research on producing crops that contain less sugars and amino acids which are the precursors. I also thin that we are all have too little knowledge about this hidden chemical. we are definitely going to need new codes of practice in the future for this and goes all the way back to the supply chain. Have you seen the ‘Go For Gold’ campaign from our FSA ?
Really important topic !