Towards the perfect soft-boiled chicken eggs: defining cooking conditions, quality criteria, and safety assessments

In recent years, ready-to-eat soft-boiled chicken eggs, with coagulated whites and semi-solid yolks have become popular among Chinese consumers due to their convenience, tender texture, and nutritional benefits. However, the standards for these products are currently inconsistent, and quality evaluation parameters and food safety issues remain unclear. Softness ratio, representing the semi-liquid yolk proportion in a cross-section, was defined through a survey of different brands of ready-to-eat soft-boiled chicken eggs. By accounting for egg weight and cooking time, optimal softness under specific conditions was determined. A quality evaluation method was established based on the softness ratio and shelling score. Finally, the safety of soft-boiled chicken eggs was assessed by measuring yolk center temperature. The optimal softness ratio was 0.46 to 0.64. Optimal cooking times in boiling water (100°C) with a 5:1 water-to-egg ratio were 300 s for 43 to 48 g eggs, 330 seconds for 48 to 53g, 350 s for 53 to 58 g, and 370 s for 58 to 63g. After cooking, eggs were cooled for 6 min in an ice water mixture with a 3:1 water-to-egg ratio. Shelling scores (0-5) depended on the egg white surface exposed post-shelling, peaking at an air cell diameter of 21.55 ± 2.26 mm. Egg weight and shelling score had a correlation of -0.41, while egg white springiness and shelling score had a correlation of 0.86. Ensuring core yolk pasteurization standards was difficult, thus stricter management or whole egg irradiation was suggested for safety.