Profiling poultry meat and eggs with metabolomics

The growing world population has led to an increase in the demand for poultry products, with a notable growth in poultry production worldwide. Meanwhile, the poultry industry needs to precisely determine the quality of poultry meat and eggs for consumers.

Metabolomics enables detailed differentiation of the biochemical indicators responsible for determining the quality of poultry meat and eggs throughout the poultry supply chain, from breed identification to the final product, without compromising bird welfare. This approach has the potential to increase the overall quality of poultry meat and egg products while preventing food fraud.

Meat quality parameters

Meat quality parameters include objective measures such as nutritional value, proximate composition, pH, water-holding capacity, total volatile base, microbial quality, shear force, drip loss, cooking loss, fibrousness, along with subjective measures, such as colour, flavour, juiciness and tenderness. Factors such as poultry feed composition and consumption, plus the rearing environment, affect the nutritional composition of poultry meat.

Egg quality parameters

Egg quality is determined by a combination of internal and external parameters, with eggs classified into 3 grades (AA, A and B). External factors include colour, size, shell thickness, height, texture, cleanliness, eggshell strength and width, while the internal factors comprise colour, viscosity of the egg white, size, colour and firmness of the egg yolk, size of the air cell and albumen height.

Nutritional quality is made up of the types and levels of protein, lipids, minerals and carbohydrates, while the egg’s nutritional composition varies in terms of shell, egg white and egg yolk, depending mainly on the genetic strain of the laying hen and is moderately affected by feed composition and consumption.

Metabolomics explained

The aim of metabolomic technology is to identify all the metabolites, including carbohydrates, amino acids, lipids, fatty acids, organic acid and vitamins, present in poultry meat and eggs. Metabolomic studies are divided into targeted and untargeted approaches. Targeted metabolomics measure and analyse specific metabolites using quantitative or semi-quantitative methods, while untargeted metabolomics identify a wider range of metabolites and detect novel compounds.

Metabolomic technology can be used to identify alterations in biological systems due to age, medication, climate, stress, pathology and temperature. Various analytical techniques are required due to the complexity and the broad physio-chemical properties of the metabolites. The most commonly used analytical platforms are nuclear magnetic resonance and mass spectrometry, along with liquid chromatography, gas chromatography and supercritical fluid chromatography.

Meat quality assessment

Various factors, such as stress, storage, pre and post-slaughter processes and geographical origin, can alter the structure and concentration of the metabolites in poultry meat. Metabolites, including indole-3-carboxaldehyde, urine monophosphate, s-phenlymercapturic acid, gluconic acid, tyramine and serylphenylalanine, determine the freshness of chilled chicken meat. In addition, spoilage bacteria such as Brochothrix, Pseudomonas and Serratia release undesired metabolites which can be recognised through a metabolomic approach.

A metabolomic approach can further prevent the development of respiratory infection in poultry at a very early stage by identifying metabolite biomarkers in the blood serum. In this way, high-quality poultry meat can be produced while minimising waste. In addition, the metabolomic approach recognises copper toxicity in broilers and reduces its environmental effects on meat quality.

Metabolomic analysis can detect different metabolites in chicken breast related to myopathy disease that affects the quality of the meat produced. Stress in poultry produces biochemical indicators, such as corticosterone, adrenal gland ascorbic acid, muscle glycogen and muscle peroxidation, which can be detected with the metabolomic approach. The metabolomic approach is particularly valuable in determining additives and drug residues, including antibiotics like quinolones, amoxicillin and tetracyclines, in poultry meat.

Egg quality assessment

Laying hen breed and feed type affect the metabolite content in chicken eggs. Metabolomics can be applied to differentiate between various types of egg and the nutrient quality of the egg yolk and egg white. Metabolomic analysis can also identify changes occurring in the egg yolk during embryonic development.

Metabolomic studies are similarly useful to determine changes in egg yolk metabolites in cooked eggs that increase specific nutritional content, such as fat-soluble vitamins, riboflavin and biotin. Microbial contamination with Salmonella, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes and Campylobacter spp alters the metabolic profile of eggs, including the metabolic pathways of amino acids and lipids. A metabolomic approach aids the identification of microbial contamination, thus preserving egg quality.

Metabolomics can also be used as a rapid, efficient and highly sensitive method of detecting antibiotic residue from Levamisole, Mebendazole and Mebendazole in poultry eggs. The metabolomic approach is further used to assess the quality of ‘designer eggs’ which are nutritionally modified or enriched beyond their natural state. However, further research is needed to integrate sensory evaluation into the metabolomic experimental design to enhance the comprehensive nature of the food quality assessment.