Furan

The level of furan has been a food safety concern for many years and is now listed by the US Dept. of Health and Human Service as a carcinogen (NTP, 2004; 2005). EFSA regard it as a compound that could lead to significant and long-term liver damage (EFSA, 2017).

It is a heterocyclic organic compound – a five membered aromatic ring of four carbon atoms and an oxygen atom.  

The chemical is formed by thermal processing and ionizing radiation which are both regularly used methods for processing foods. It is found in heat-treated foods like coffee, canned meat, baked bread, roasted meats and nuts. From a sensory perspective, it is an important contributor to roasted and cooked food flavour (Merritt et al., 1963; Maga, 1979). The aroma and flavour of coffee especially benefits from its presence. 

The amount of furan can be as high as 350 ng/g food as reported for nuts (Cha & Lee, 2020).

Furan forms via the vast array of Maillard reactions which are responsible for browning and flavour creation. It forms from conversion of sugars such as sucrose, fructose and glucose, and from vitamin C (ascorbic acid), from amino acids, carotenoids and unsaturated fatty acids.

The levels and routes for its formation from such compounds has been established by studying model systems using mixtures of amino acids and sugars (Limacher et al., 2008). It is thought that the formation of furan by thermal means is a different chemical mechanism to that formed by irradiation. 

More furan forms from sucrose and fructose than glucose but none at all from starch(Fan, 200b). 

More furan  is formed from erythorbic acid than ascorbic acid (Becalski & Seaman, 2005) when it follows a thermal mechanism. 

PUFAs (polyunsaturated fatty acids) are a source of furans. When heated, PUFAs result in lipid peroxidation products like 2-alkenal, 4-oxo-alkenal, 4-hydoxy-2-alkenal, and 4-hydroxy-2-butanal with furan as a byproduct (Cha & Lee, 2020). Becalski and Seaman demonstrated that model systems heated at 118◦C for 30 minutes showed only PUFAs, especially linoleic and linolenic acids, will  generate furan during heating (Becalski & Seaman, 2005; Yaylayan, 2006).

Furan is formed when nuts are roasted (Cha & Lee, 2020). As the roasting temperature and time increase, so does the amount of furan and that aspect of cooking is seen in other foods. From a reaction kinetics perspective,  production of furan in nuts follows the zero-order kinetic model.

Related derivatives, 2-methylfuran and 3-methylfuran are also formed from similar substrates. Other derivatives include 4-hydroxy furan and 2,5-dimethylfuran.

The formation of furan has been extensively reviewed over a number of years (Maga, 1979; Crews et al., 2007).

Coffee

Furan is formed 

Measurement

The analysis of furan in food is not straightforward because of its high volatility and low molecular weight. The 1st quantitative method for furan in food was published by the  FDA using headspace extraction coupled with GC-MS (HS-GC-MS) method (FDA 2004).

Furan is analysed using gas chromatography-mass spectrometry (GC-MS) with headspace sampling and solid phase microextraction (SPME) as the sample preparation methods (Bekalski et al., 2005; Fan, 2005a&b; Goldmann et al., 2005). A very recent method has been described using GC-MS/MS with HS-SPME-Arrow (Huang et al., 2022).

References

Altaki, M.S., Santos, F.J., Galceran M.T. (2007). Analysis of furan in foods by headspace solid-phase microextraction-gas chromatography-ion trap mass spectrometry. J Chromatogr. A 1146 pp. 103–9 (Article).

Becalski A, Seaman S. 2005. Furan precursors in food: a model study and development of a simple headspace method for determination of furan. J. AOAC Int. 88 pp. 102–6

Becalski A, Forsyth V, Casey V, Lau BPY, Pepper K, Seaman S. (2005) Development and validation of a headspace method for determination of furan in food. Food Addit. Contam. 22 pp. 535–40

Cha, C.-Y., Lee, K.-G. (2020) Effect of roasting conditions on the formation and kinetics of furan in various nuts. Food Chem., 331 30 Nov. 127338 (Article)

Crews, C., & Castle, L. (2007). A review of the occurrence, formation and analysis of furan in heat-processed foods. Trends in Food Science & Technology, 18(7), 365-372.

EFSA (2017) Furan in food – EFSA confirms health concerns. (Article) Accessed 6th September 2022.

Fan X. 2005a. Formation of furan from carbohydrates and ascorbic acid following exposure to ionizing radiation and thermal processing. J Agric Food Chem 53 pp. 7826–31 (Article)

Fan X. 2005b. Impact of ionizing radiation and thermal treatments on furan levels in fruit juice. J Food Sci. 71:E409–E14.

Goldmann, C.P., Perisset A, Scanlan F, Stadler RH. (2005). Rapid determination of furan in heated foodstuffs by isotope dilution solid phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS). Analyst 130 pp. 78–83 (Article).

Huang, Y. H., Kao, T. H., & Chen, B. H. (2022). Development of a GC–MS/MS method coupled with HS-SPME-Arrow for studying formation of furan and 10 derivatives in model systems and commercial foods. Food Chemistry, 395, 133572.

Limacher A, Kerler J, Davidek T, Schmalzried F, Blank I. 2008. Formation of furan and methylfuran by maillard-type reactions in model systems and food. J Agric Food Chem 56 pp. 3639–47 (Article) 

Maga JA. 1979. Furans in foods. Crit Rev Food Sci 4 pp. 355–400

Merritt C, Bazinet ML, Sullivan JH, Robertson DH. (1963). Mass spectrometric determination of the volatile components from ground coffee. J Agric Food Chem. 11 pp. 152–5 (Article) .

NTP, (2004) National Toxicology Program. 2004. Furan CAS Nr. 110-00-9. Report on carcinogens. 11th ed. U. S. Dept. of Health and Human Services, Public Health Service, 2004. 

Yaylayan V. Precursors, formation and determination of furan in food. J. Verbrauch Lebensm. (2006) 1: pp. 5–9 (Article)