Detection of falsified maize gluten

Different methods have been employed to detect falsified maize gluten products. Microscopic observations -numerous starch grains, seed envelopes and wheat bran fragments- clearly showed the presence of atypical maize gluten particles in samples with otherwise normal crude protein levels (≥ 60%) and the usual gold-yellow color. Chemical analyses in a few samples confirmed the presence of urea (19 to 173 g/kg), melamine (up to 20 g/kg) and cyanuric acid (up to 10 g/kg) coping for the low levels of methionine (up to 13 g/kg) in incriminated products (genuine maize gluten methionine level ≥ 16 g/kg). Furthermore, a fast technique – an electronic nose based on mass spectrometry detection- also proved to be reliable for the identification of falsified maize gluten products: 100% correct classification of model and unknown samples was achieved with principal component analysis. As a consequence of these results, the Swiss feed-inspection authority blocked the import, or restricted the use, of 2500 tons of falsified products.