An investigation into the detection of fraud during poultry egg production: a metabonomic approach using liquid chromatography - mass spectrometry

Abstract

Food fraud is becoming an increasingly difficult challenge, with the ongoing global expansion of food supply chains. Previously developed methods have been successful in the detection of some instances of food fraud, however they struggle to detect more subtle examples of fraud. Eggs are a food product that are susceptible to fraud, as the differences between authentic and fraudulent eggs are extremely subtle and difficult to detect. The intention of this work was to reveal how a metabonomic approach, using liquid chromatography quadrupole-time-of-flight mass spectrometry followed by robust statistical analysis, can be used to observe how different conditions and factors in the production of poultry eggs affect the metabolite profiles of the yolk and albumen of the eggs. It aimed to show how the observed differences between the eggs can lead to the detection and identification of compounds that have potential as markers capable of detecting instances of fraud.
The first study, and some aspects of the following two studies, conducted during this research involved some preliminary work, and were carried out in order to optimise the experimental designs for the remaining studies carried out throughout this research. The optimum storage temperature and condition of metabolite extracts was determined, and it was concluded that the age and diet of the laying birds should be kept the same both with in and between experimental groups in the same study.
The metabolite profile of the egg, particularly the albumen, was found to be affected by the age of the bird, and a compound found in the albumen that showed potential as a marker of hen age was putatively identified. It was observed that different diets of the hen affect the metabolite profile of the egg differently, and that they affect the egg at varying rates. Choline was discovered to be a suitable marker of egg age when eggs are stored at 23 °C, however refrigerated egg storage was found to inhibit its use as a marker. Some putatively identified compounds were determined to have potential use as markers of liquid yolk storage time at 5 °C. The cage stocking density of birds was found to have an effect on the metabolite profile of egg yolk, which was independent of the effect of cage population size. A compound that showed some potential as a marker of cage stocking density was putatively identified. Several potential lipids were found to have a higher abundance in barn egg yolk compared to cage egg yolk, and one of these potential lipids as putatively identified. Little difference was observed between the albumen metabolite profiles of eggs from different housing systems. The research presented in this thesis reveals that a metabonomic approach, using liquid chromatography-mass spectrometry, can be successful in uncovering subtle differences between eggs from different backgrounds. It show show this metabonomic approach, and the observed differences, can be applied to the development of methods for the potential detection of fraud in the production and marketing of poultry eggs.