RESUMO
Sustenance of smallholder poultry production as an alternative source of food security and income is imperative in communities exposed to hydrocarbon pollution. Exposure to hydrocarbon pollutants causes disruption of homeostasis, thereby compromising the genetic potential of the birds. Oxidative stress-mediated dysfunction of the cellular membrane is a contributing factor in the mechanism of hydrocarbon toxicity. Epidemiological studies show that tolerance to hydrocarbon exposure may be caused by the activation of genes that control disease defense pathways like aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2p45-related factor 2 (Nrf2). Disparity in the mechanism and level of tolerance to hydrocarbon fragments among species may exist and may result in variations in gene expression within individuals of the same species upon exposure. Genomic variability is critical for adaptation and serves as a survival mechanism in response to environmental pollutants. Understanding the interplay of diverse genetic mechanisms in relation to environmental influences is important for exploiting the differences in various genetic variants. Protection against pollutant-induced physiological responses using dietary antioxidants can mitigate homeostasis disruptions. Such intervention may initiate epigenetic modulation relevant to gene expression of hydrocarbon tolerance, enhancing productivity, and possibly future development of hydrocarbon-tolerant breeds.
RESUMO
Albumen quality is recognized as one of the major yardsticks in measuring egg quality. The elasticity of thick albumen, a strong bond in the ovomucin-lysozyme complex, and excellent biological properties are indicators of high-quality albumen. The albumen quality prior to egg storage contribute to enhance egg's shelf life and economic value. Evidence suggests that albumen quality can deteriorate due to changes in albumen structure, such as the degradation of ß-ovomucin subunit and O-glyosidic bonds, the collapse of the ovomucin-lysozyme complex, and a decrease in albumen protein-protein interaction. Using organic minerals, natural plants and animal products with antioxidant and antimicrobial properties, high biological value, no residue effect and toxicity risk could improve albumen quality. These natural products (e.g., tea polyphenols, marigold extract, magnolol, essential oils, Upro (small peptide), yeast cell wall, Bacillus species, a purified amino acid from animal blood, and pumpkin seed meal) are bio-fortified into eggs, thus enhancing the biological and technological function of the albumen. Multiple strategies to meeting laying hens' metabolic requirements and improvement in albumen quality are described in this review, including the use of amino acids, vitamins, minerals, essential oils, prebiotics, probiotics, organic trace elements, and phytogenic as feed additives. From this analysis, natural products can improve animal health and consequently albumen quality. Future research should focus on effects of these natural products in extending shelf life of the albumen during storage and at different storage conditions. Research in that direction may provide insight into albumen quality and its biological value in fresh and stored eggs.
RESUMO
Enhanced albumen quality is reflected in increased thick albumen height, albumen weight, and Haugh unit value, while the antimicrobial, antioxidant, foaming, gelling, viscosity, and elasticity attributes are retained. Improved albumen quality is of benefit to consumers and to the food and health industries. Egg quality often declines during storage because eggs are highly perishable products and are most often not consumed immediately after oviposition. This review provides insights into albumen quality in terms of changes in albumen structure during storage, the influence of storage time and temperature, and the mitigation effects of natural dietary antioxidants of plant origin. During storage, albumen undergoes various physiochemical changes: loss of moisture and gaseous products through the shell pores and breakdown of carbonic acid, which induces albumen pH increases. High albumen pH acts as a catalyst for structural changes in albumen, including degradation of the ß-ovomucin subunit and O-glycosidic bonds, collapse of the ovomucin-lysozyme complex, and decline in albumen protein-protein interactions. These culminate in declined albumen quality, characterized by the loss of albumen proteins, such as ovomucin, destabilized foaming and gelling capacity, decreased antimicrobial activity, albumen liquefaction, and reduced viscosity and elasticity. These changes and rates of albumen decline are more conspicuous at ambient temperature compared to low temperatures. Thus, albumen of poor quality due to the loss of functional and biological properties cannot be harnessed as a functional food, as an ingredient in food processing industries, and for its active compounds for drug creation in the health industry. The use of refrigerators, coatings, and thermal and non-thermal treatments to preserve albumen quality during storage are limited by huge financial costs, the skilled operations required, environmental pollution, and residue and toxicity effects. Nutritional interventions, including supplementation with natural antioxidants of plant origin in the diets of laying hens, have a promising potential as natural shelf-life extenders. Since they are safe, without residue effects, the bioactive compounds could be transferred to the egg. Natural antioxidants of plant origin have been found to increase albumen radical scavenging activity, increase the total antioxidant capacity of albumen, reduce the protein carbonyl and malondialdehyde (MDA) content of albumen, and prevent oxidative damage to the magnum, thereby eliminating the transfer of toxins to the egg. These products are targeted towards attenuating oxidative species and inhibiting or slowing down the rates of lipid and protein peroxidation, thereby enhancing egg quality and extending the shelf life of albumen.
