Abstract
Adulteration may consist in non authorized source of nitrogen addition to increase the protein content of some raw materials. Urea which is authorized for feed is a non nutritional source of nitrogen in food and pet food. Adulteration of food or pet food raw material by urea is thus monitored by manufacturer and governmental authorities with official methods which are either enzymatic (Association of Official Agricultural Chemists, AOAC) or spectro-colorimetric (European Community, EC). Each method gives results which are not comparable and spectro-colorimetric methods may result in false-positive urea detection. Liquid chromatographic (LC/UV-DAD) analysis of extracts from spectro-colorimetric method indicates that presence of free amino-acid may interfere with colorimetric detection of urea in the EC method with pet food samples. Liquid chromatography electrospray ionization high resolution mass spectrometry (LC/ESI-HRMS) has allowed to quantify low content (<0.01%) of urea in pet food water extracts for samples which resulted in significant urea detection with colorimetric method and in content below the detection threshold with enzymatic method. This study demonstrates the EC colorimetric method is not applicable to pet food and also food samples which have a complex composition with significant levels of free amino acids. On the other hand we clearly evidenced by means of the LC/ESI-HRMS results that the AOC Enzymatic method is applicable to urea quantification in pet food samples and gives reliable results.
Highlights
Non authorized food ingredient can be used to adulterate ingredients, raw materials (e.g. Gluten) or finished product to artificially increase the protein content
This study demonstrates the European Commission Regulation (EC) colorimetric method is not applicable to pet food and food samples which have a complex composition with significant levels of free amino acids
The EC colorimetric method for urea analysis is not applicable to dry petfood products as interfering molecules result in significant urea concentration over dosing
Summary
Non authorized food ingredient can be used to adulterate ingredients, raw materials (e.g. Gluten) or finished product (e.g. milk products) to artificially increase the protein content. For instance, has been used as the food additive to increase the apparent protein content in food products [1]. Ruminant can convert non protein nitrogen into protein and urea may be used to increase the nutritional nitrogen content of feed, hay or silage. Urea is authorized as a component of animal feeds to provide nutritional source of nitrogen. Urea is accepted as a “Generally Recognized as Safe” food additive and is used as a fermentation aid in foods and beverages [2]. Urea is produced in the liver of mammals as an endproduct of protein metabolism and excreted in urine. Humans excrete up to 30 grams of urea per day in the urine [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
