Detection of Urea Adulteration in Oilseed Cakes using 4-Dimethylaminobenzaldehyde Reagent and Foldscope

Costly livestock feed ingredients like oilseed cakes are more frequently adulterated with urea by feed manufacturers and suppliers to derive economic benefit. However, a simple method to detect adulteration of urea in oilseed cakes under field conditions is not available. In this context, the present study was carried out to evaluate the usefulness of 4-dimethylaminobenzaldehyde reagent for the detection of urea adulteration in oilseed cakes using foldscope under field conditions.

Six commonly used oilseed cakes for livestock feeding were procured from three different sources and processed in duplicate. A minute quantity of dry powdered oilseed cake or oilseed cake adulterated with urea (10 g/kg) was taken on a glass slide, treated with 4-dimethylaminobenzaldehyde reagent and air dried. The air dried sample was spread and covered with transparent cello tape and examined under foldscope with a standard light source. The foldscope images were captured using smart phone camera. Approximate area covered with yellow colour in foldscope images of oilseed cakes adulterated with urea at three different concentrations also evaluated.

Oilseed cakes adulterated with urea on treatment with 4-dimethylaminobenzaldehyde reagent showed yellow colour covering almost entire area of many fields in foldscope images, while the colour of oilseed cakes devoid of urea was mostly pink to violet. The oilseed cakes adulterated with urea at different concentrations varied in the approximate area covered with yellow colour in foldscope images. The 4-dimethylaminobenzaldehyde reagent can be used to detect urea adulteration in oilseed cakes using foldscope under field conditions.