Overview on recent findings of nutritional and non-nutritional factors affecting egg yolk pigmentation

SUMMARYThe colour of the egg yolk is one of the most important sensory characteristics among consumers and is often perceived as a health and quality component of the product. Carotenoids found in hen diet are the main components contributing to the yolk pigmentation, and therefore, nutrition is a major factor influencing the yolk quality and colour. The ratio of yellow and red carotenoid pigments is of great importance in achieving the desired yolk colour. The difficulties associated with the optimum carotenoid concentration in the diet arise from the considerable variation in amounts in feeds and bioavailability from the sources used, synthetic or phytochemical. In addition, the carotenoid content in phytochemical sources is not always constant, and it is necessary to consider their interaction with other components in the diet, as well as denaturation during processing or loss during prolonged storage. Laying hens are unable to synthesise carotenoids de novo and depend on their supply through the diet. For this reason, pigmentation can decrease due to reduced diet intake, which a number of factors can influence. The housing system affects yolk pigmentation due to differences in applied nutritional management. In addition, reduced diet intake, carotenoid utilisation for health defence and reduced absorption occurs in response to stress conditions and various diseases. The objective of this review was to summarise the recent findings in available literature data on nutritional and non-nutritional factors affecting egg yolk pigmentation.