A study published in LWT - Food Science and Technology has suggested that crayfish protein extracted from a flour-like by-product powder produces a stable emulsion with good behaviour at the oil/water interface, and may have potential applications in the food industry.
“We have demonstrated that crayfish proteins at pH 8 show higher solubility, smaller aggregates and better interfacial activity (higher surface pressure and lower interfacial tension) with higher interfacial viscoelasticity,” wrote the authors, led by Alberto Romero at the department of chemical engineering at the University of Sevilla, Spain.
The researchers said that the results “confirm the relevance … as well as the excellent potential” of crayfish proteins as a food emulsifier.
By-processing
“Much of the food industries, particularly those involved in primary production, generate large amounts of waste and by-products,” explained Romero and his colleagues.
They said that some processing by-products can be evaluated “with the aim of producing added value products” such as biomaterials, functional food ingredients or ingredients for other food applications – such as use in emulsions.
Emulsion stability
“Oil / water emulsions are complex systems whose properties depend on the specific characteristics of the three component parts: the oily disperse phase, the continuous aqueous phase and the interface,” said the authors.
They explained that to understand the properties of an emulsion it is necessary to consider the properties of each phase, “but it is essential to focus specifically on the interface.”
The interface of an oil / water emulsion for food applications is generally composed of proteins, or low molecular weight emulsifiers. It is therefore important to understand how potential emulsifying proteins behave at the interface, and how this affects stability, said the authors.
“The overall objective of this study is to evaluate crayfish protein potentials as emulsifier in relation to its air/water and oil/water interfacial behaviour, which may help to select optimal conditions in order to enhance emulsion stability,” explained Romero and co-workers.
Study details
Crayfish flour was manufactured on a pilot scale by separating the exoskeleton from comminuted (pulverised) material, to form a crayfish “meat slurry”, which was then dried to obtain a powder.
From this, the researchers extracted a crayfish protein isolate, which was tested for its ability as an emulsifying protein.
The authors reported the crayfish protein isolate to vary in its solubility behaviour dependent on pH. However, they observed that the protein molecules aggregate at both acidic and alkaline pHs.
“Although emulsions at pH 2 and 8 show the same interfacial protein concentration, systems at pH 8 exhibit smaller aggregates, higher solubility and better interfacial values (higher surface pressure and lower interfacial tension) with higher interfacial viscoelasticity,” said the authors.
The researchers said a pH dependent relationship was found between parameters from oil-water and air-water interfaces.
“Crayfish proteins confer an elastic dominant behaviour to oil-water interfaces showing low interfacial tension values … however, these proteins show a relatively low complex dilatational modulus [related to deformation resistance] in comparison to the values found for globular proteins,” said the authors.
Romero and his colleagues said that further research devoted to exploring a range of potential food applications is now required.
Source: LWT - Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2011.03.005
“Interfacial and emulsifying behaviour of crayfish protein isolate”
Authors: A. Romero, V. Beaumal, E. David-Briand, F. Cordobes, M. Anton, A. Guerrero