Abstract
AbstractEggs are commonly used in the food industry because of their excellent nutrient value and also for their coagulating, foaming, emulsifying, colouring and flavouring properties. Manufacturers substitute shell eggs with processed egg products, such as liquid whole egg, liquid egg yolk or albumin. They have a shelf life of a few weeks, but freezing can increase it to 1 year. However, freezing causes gelation in case of egg yolk. This process is highly dependent on the conditions of freezing and thawing.In our study, raw liquid egg yolk was frozen and stored for 14 days at −18 °C. On days 1, 7 and 14 samples were thawed by two different methods. Denaturation temperature and enthalpy were investigated by differential scanning calorimetry. Besides, rheological properties were examined at 20 °C, Herschel–Bulkley model was fitted to flow curves of the examined samples. The dry matter content was also recorded during the experiment. Two-way ANOVA was used to analyse data.The results of the study showed that method of thawing had no significant effect on calorimetric and rheological properties and dry matter content. In contrast, freezing and frozen storage had a significant effect on denaturation enthalpy and rheological properties.
Highlights
The egg yolk is a popular ingredient in the food industry because of its emulsifying, gelling and coagulating properties (Primacella et al, 2020)
We examine the effect of slow freezing and different thawing methods on the rheological and calorimetric properties of raw liquid egg yolk
The dry matter content of the samples was examined during storage
Summary
The egg yolk is a popular ingredient in the food industry because of its emulsifying, gelling and coagulating properties (Primacella et al, 2020). Studies about denaturation properties of egg and egg parts by DSC are not new (but most of the authors examined egg white (H€ohne et al, 2003; Biliaderis, 1983; Cordobes et al, 2004; Rossi and Schiraldi, 1992; Ferreira et al, 1997; Donovan et al, 1975; Duan et al, 2017; Igarashi et al, 1999) In their differential scanning calorimetric study, Wootton et al (1981) showed that denaturation enthalpy can be reduced by decreasing the freezing rate, increasing the thawing rate and increasing the storage temperature and storage time in case of liquid egg white. We examine the effect of slow freezing and different thawing methods on the rheological and calorimetric properties of raw liquid egg yolk. Dry matter content is measured for the better understanding of the gelation process
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