Japan has become a “super-aged society” in which over 21% of the population is aged≥65 years. Many Japanese people are seeking functional foods that can prevent age-related diseases. Thus, we developed and applied a method of evaluating anti-aging foods based on age-related hearing loss (AHL) in mice. We found that the intake of a diet containing whole egg (8% or 20% of the diet) or 13.6% egg yolks for 6 months delayed the development of AHL, whereas a diet containing 6.4% egg whites had no effect. This indicates that egg yolk has the potential to prevent age-related diseases.
Eggs of the Nagoya breed of chickens are characterized by a bright cherry blossom-colored eggshell and a thick, full-flavored yolk. The eggshell is covered by white spots of calcium carbonate, while the yolk has a deep color and a higher ratio of yolk weight compared to that of White Leghorn chickens. As for nutritional characteristics, the lipid content of the yolk is significantly higher in Nagoya compared to that in White Leghorn. As for physical characteristics, the yolk viscosity of eggs is higher in Nagoya than that in White Leghorn. Recent findings using an artificial taste sensor revealed the high umami taste intensity of Nagoya egg yolk compared to that of White Leghorn. As for processing properties, the emulsifying ability of the yolk of Nagoya is superior to that of White Leghorn. The hardness and elastic modulus are high in the boiled eggs of Nagoya compared to those of White Leghorn. From these findings, Nagoya eggs are characterized by the yolk. Thus, it is proposed that this characteristic is one of factors responsible for the palatability of eggs of Nagoya chickens.