Smartphone-based colorimetric study of adulterated tuna samples

•Tuna samples were adulterated with NaNO2 and NaNO3, as well as vegetable extracts.•HPLC-DAD was applied to quantify the amount of NaNO2 and NaNO3 in the samples.•Colorimetric analysis was made using a smartphone and a spectroradiometer.•Beetroot and nitrite were the most effective treatments, maintaining red colour.•Colour allows to objectively discriminate between adulteration methods. In this work, a colorimetric analysis of adulterated tuna samples is carried out using both a spectroradiometer and a smartphone as capture devices. Yellowfin tuna (Thunnus albacares) slices were treated with nitrate and nitrite salts, as well as with two different vegetable extracts (beetroot and radish), and the resulting NO2– and NO3– concentration was analysed using HPLC-DAD. The results indicate that both nitrite and beetroot treatments work properly as colouring agents in tuna, being nitrate also effective. When assessing the effect of radish, the final flesh had a more whitish colour. Overall, this approach allows to obtain colorimetric data which can distinguish among the different adulterating agents.