Overview
Le Gresley and colleagues bought French fries from two fast-food chains in the UK at nine time points over three days in late 2018, extracted the frying oil with n-hexane, and measured lipid oxidation products by NMR and trace metals by ICP-OES. This record covers lead only. Lead in the oil extracted from chain X fries was about twice that from chain Y.
Key numbers
- Chain X fry oil extract: lead overall average 175.32 µg/kg oil, highest time point 355.10 ± 16.47 µg/kg (Table 4, p. 14).
- Chain Y fry oil extract: lead overall average 76.79 µg/kg oil (Table 4, p. 15).
- Per 30 g serving: 3.37 µg lead (chain X) and 3.36 µg (chain Y), overall averages (Table 7, p. 20).
Methods (brief)
Fries were blended with n-hexane to extract the absorbed oil; 0.5 g of oil was microwave-digested with nitric acid and hydrogen peroxide and analysed by ICP-OES with reagent blanks, in duplicate. No reference material is reported and LOQs are only in the supplement.
Evidence Fitness
Two restaurants, duplicate portions per time point, and lead measured in the extracted oil rather than the whole fry, so values are not fry concentrations. Per-serving amounts are the authors’ derivation. Fried potato is a proxy for cream-of-potato-soup, so that page is not linked. Other metals in the tables were not extracted, by owner instruction.