Evaluation of egg yolk colour

Abstract

We compare visual evaluation of yolk colour estimated by the usual method applying La Roche scale with spectrophotometric determination of β-carotene by AOAC method, and by new rapid analyser iCheckTM Egg photometer (BioAnalyt). The eggs under consideration were purchased on a current Czech market. The eggs originated from various countries and various types of breeding including some specialities. The yolk colour varied between the values of 4-13 of La Roche scale. The carotenoid content expressed as β-carotene measured by AOAC method varied between 11-87 mg/kg. The carotenoid content expressed as β-carotene measured with the analyser iCheckTM Egg photometer was lower and varied between 7.5-68.5 mg/kg. The correlation between the colour hue measured visually and the carotenoid content was not proved. Slovak eggs from cages which contained 28.3 mg carotenoids in 1 kg of yolk had the darkest yolks (value 13), Czech bio eggs which contained 20.2 mg carotenoids in 1 kg of yolk had the palest yolks (value 6). The highest content of carotenoids was found in eggs from home hen breeding (72.5 mg carotenoids in 1 kg of yolk) whose colour hue had the value of 10.

Keywords

• carotenoid determination
• analyser ichecktm egg photometer
• sensory visual evaluation