To elucidate which markers of ultra-processing (MUP) and their combinations are best suited to detect ultra-processed food (UPF).

The study was based on the 206 food and 32 beverage items of the Oxford WebQ which encompass all major foods consumed in the UK. For each Oxford WebQ question, ingredient lists of up to ten matching different commercial products (n 2146) were researched online using data from the two market leaders of groceries in the UK sorted by relevance (Tesco) and by top sellers (Sainsbury’s), respectively. According to the NOVA classification, sixty-five MUP were defined, and if the ingredient list of a food product was positive for at least one MUP, it was regarded as UPF. The percentage of UPF items containing specific MUP was calculated. In addition, all combinations of two to six different MUP were assessed concerning the percentage of identified UPF items.

Cross-sectional analysis.

None.

A total of 990 products contained at least one MUP and were, therefore, regarded as UPF. The most frequent MUP were flavour (578 items, 58·4 % of all UPF), emulsifiers (353 items, 35·7 % of all UPF) and colour (262 items, 26·5 % of all UPF). Combined, these three MUP detected 79·2 % of all UPF products. Detection rate increased to 88·4 % of all UPF if ingredient lists were analysed concerning three additional MUP, that is, fibre, dextrose and firming agent.

Almost 90 % of all UPF items can be detected by six MUP.