Abstract
Egg yolk is a multifunctional ingredient widely used in many food products, wherein proteins are the dominant component contributing to this functionality. However, the potential risk of foodborne illness associated with egg use forces us to ensure that foodstuffs based on egg yolk are managed in a safe and sanitary manner. Lowering the pH under a certain value by adding acids could serve this purpose, but it can also greatly modify the rheological and functional properties of egg yolk. This research aims to assess the influence of citric acid on the rheological properties and microstructure of chicken egg yolk dispersions and their heat-set gels. The dispersions were prepared from fresh hen’s eggs yolks by adding water or citric acid to obtain a technical yolk (45 wt.% in solids) at the desired pH value. Viscoelastic measurements were carried out using a control stress rheometer, and microstructure was evaluated by cryo-scanning electronic microscopy (CryoSEM). An evolution of the viscoelastic properties of egg yolk dispersions from fluid to gel behavior was observed as the pH decreased until 2 but showing a predominantly fluid behavior at pH 3. The profile of viscoelastic properties along the thermal cycle applied is modified to a great extent, also showing a strong dependence on pH. Thus, the sol–gel transition can be modulated by the pH value.
Highlights
In solids) at the desired pH value
Egg yolk is a key ingredient in the manufacture of foodstuffs such as sauces, desserts, baked goods, or ready meals, which need to be subjected to a gelation process [4,5]
5A.6), the hydrovalues both viscoelastic properties occurredcycle for all the cases the pH moved phobicofinteractions induced by the thermal applied are studied
Summary
In solids) at the desired pH value. Viscoelastic measurements were carried out using a control stress rheometer, and microstructure was evaluated by cryo-scanning electronic microscopy (CryoSEM). An evolution of the viscoelastic properties of egg yolk dispersions from fluid to gel behavior was observed as the pH decreased until 2 but showing a predominantly fluid behavior at pH 3. Eggs have been classically recognized as a high nutritional source of protein, being cheaper than fish or meat. This growth undergone in the past two decades may be associated with the change in medical criteria regarding the erroneous negative effect of egg consumption on health [2]. From a nutritional point of view, eggs contain high-quality proteins and provide a high number of essential micronutrients such as minerals and vitamins, apart from having a low calorific value due to their moderate and well-balanced lipid content. Egg yolk (EY) may be considered as an oil-in-water emulsion, almost half of it composed by water, where lipids and proteins (a third and a sixth part of EY, respectively) are suspended in the “aqueous phase”, mainly associated as lipoprotein complexes [6,7]
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