Detection of falsified maize gluten

Agroscope Liebefeld-Posieux ALP employed different methods to detect falsified maize gluten products. Microscopic observations - numerous starch grains, seed envelopes and wheat bran fragments - clearly showed atypical maize gluten particles in samples with otherwise normal crude protein levels (>= 60%) and usual gold-yellow colour. Chemical analyses in these samples confirmed presence of urea (19 to 173 g/kg), melamine (up to 20 g/kg) and cyanuric acid (up to 10 g/kg) as well as low levels of methionine (in most cases < 2.5 g/kg) in incriminated products (genuine maize gluten methionine level >= 16 g/kg). Furthermore, a fast technique - 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. These results made Swiss feed-inspect ion authority prohibit or restrict the use of 2500 tons of falsified products.