According to the researchers from the University of Massachusetts the results offer possibilities for low calorie foods by reducing the need for sucrose to be added to stabilise the emulsion during freezing and subsequent thawing.
"It shows that the amount of cryoprotectant (sucrose) needed to stabilize an emulsion against freezing and thawing may be reduced by coating the oil droplets with thick biopolymer layers," wrote lead author Yeun Suk Gu in the Journal of Food Engineering.
"This may be important for the development of reduced calorie foods."
According to background information by the authors, many oil-in-water emulsions can breakdown when they are frozen, with the formation of clumps due to crystallisation of either the fat and/or water phases and a coming together of the dispersed particles.
The new research, led by Professor D. Julian McClements, reports that this phenomena "limits their utilization in certain types of food applications," explained the authors.
The authors of the new study prepared three corn oil-in-water emulsions (five per cent, weight for weight) using layer-by-layer electrostatic deposition of one of three biopolymers: only beta-lactoglobulin (why protein); beta-lactoglobulin plus iota-carrageenan; or beta-lactoglobulin plus iota-carrageenan plus fish gelatin. Davisco Food International, FMC BioPolymer and Norland Products for donating the ingredients, respectively.
The resulting emulsions were then subjected to between one to three freezethaw cycles consisting of minus 20 degrees Celsius for 22 hour, then rising to plus 40 Celsius for two hours with or without of 10 per cent sucrose.
The researchers report: "In the absence of sucrose, the primary and secondary emulsions were highly unstable to droplet aggregation and creaming after three freezethaw cycles, whereas the tertiary emulsion was stable, which was attributed to the relatively thick biopolymer layer surrounding the oil droplets."
The stability of each of the emulsions improved significantly on the addition of sucrose, said to be due to the ability of sucrose to lower the freezing point of the aqueous phase in the emulsions and stop them from freezing.
Taken together, the researchers said that the use of these biopolymers could ultimately lead to the production of food emulsions with improved stability to freezing and thawing.
"Nevertheless, further work is needed to study how the characteristics of the biopolymer interfacial layer surrounding the lipid droplets change during freezing, how they influence the formation of ice crystals, and how they affect the interactions between emulsion droplets," said the researchers.
"In particular, it would be useful to study the effects of different kinds of cosolvents (e.g., glycerol, sorbitol, monosaccharides, disaccharides and oligosaccharides) on the freezethaw stability of emulsions," they said.
Source: Journal of Food Engineering
Volume 80, Issue 4, Pages 1246-1254
"Application of multi-component biopolymer layers to improve the freezethaw stability of oil-in-water emulsions: beta-Lactoglobuliniota-carrageenangelatin"
Authors: Y.S. Gu, E.A. Decker and D.J. McClements