A Rheological Study of Lemon Curd Made of Frozen-thawed Liquid Egg Yolk

Abstract

In this study, we examined the industrial usability of frozen and thawed liquid egg yolk (LEY) by preparing lemon curd samples. Therefore, LEY frozen at-18°C was used to make lemon curd samples. LEY was stored for 90 days at -18°C and it was thawed with two different methods (in 2 hours, 35°C and in 24 hours, 5°C) on measurement days (day 1, 7, 14, 30, 60 and 90). After thawing of LEY samples, lemon curd samples were made by adding liquid egg white, butter, lemon juice and sugar. Ingredients were mixed by constant whisking over the steam of hot water. After that, butter was also added to the cream and it was cooled to 20°C. Rheological parameters of the lemon curd samples were examined with rotational rheometer. Shear stress data were recorded by increasing, than by decreasing shear rate values in the range of 10-1000 1/s. Herschel-Bulkley model was fitted to the flow curves of decreasing shear rate. Based on our measurements, we found that the thawing method of frozen liquid egg yolk does not affect the rheological properties of lemon curd made of them, but the length of the frozen storage does.