Researchers find way of protecting anthocyanins in isotonic drinks
The authors of a study published in the International Journal of Food Science and Technology found that such carrier agents allowed uniform microcapsules with spherical surface and led to the longest anthocyanin half-life time and lowest degradation constant under all conditions evaluated.
Colour is one of the most important attributes in food and drinks, as it affects the acceptability of products by consumers, said the researchers, who note the increasing shift to natural food colourants from synthetic dyes by food and drink manufacturers.
And anthocyanins, continued the researchers, are an attractive alternative to synthetic colours, as they provide high colourant power, low toxicity and water solubility.
The pink to purple water-soluble flavonoids are naturally occurring pigments in many fruits and red wine and have claimed health benefits.
In both in vitro and in vivo studies, anthocyanins tend to reduce cancer cell proliferation and inhibit tumour formation, report the team, who added that research has demonstrated that anthocyanins also protect against cardiovascular disease.
However, anthocyanins are sensitive to degradation by high pH, light and temperature.
“There are limitations to the application of anthocyanins as pigments in food systems related to the process conditions, formulation and storage conditions. This has stimulated a search for new methods to enhance their stability and increase the possibilities for the use these compounds,” explained the team.
The study
The authors said the aim of the research was to establish the optimal conditions for anthocyanin extraction from Cabernet Sauvignon (Vitis vinifera L.) grapes, employing response surface methodology (RSM).
They added that they subsequently set out to evaluate the stability of these anthocyanins encapsulated with different carrier agents - maltodextrin, maltodextrin/γ-cyclodextrin and maltodextrin/arabic gum - in a soft drink model system under different light and temperature conditions.
The researchers said that the RSM approach evaluated the effects and interactions of the solvent volume, extraction time and pH of the solution in terms of anthocyanin extraction from the Cabernet Sauvignon grapes.
The said that encapsulated anthocyanin extracts were added to an isotonic soft drink system (sucrose 4 per cent, citric acid 0.38 per cent, glucose 0.15 per cent, sodium chloride 0.12 per cent, sodium citrate 0.11 per cent and potassium monophosphate 0.022 per cent), considering a commercial isotonic soft drink colour as the reference.
To evaluate the colourant stability, the team added that 5 mL samples of the isotonic soft drink system were transferred to screw-top test tubes and kept under three conditions: under a 40 W fluorescence lamp at 25 ± 1 °C; in the absence of light at 25 ± 1 °C; and in the absence of light at 4 ± 1 °C.
Samples were withdrawn to quantify the content of anthocyanins at regular intervals for 40 days.
The researchers determined that the optimum combination of independent variables for anthocyanin extraction was 40 mL ethanol:1.5 N HCl (85:15) solution and an extraction time of 29.4 h at pH 2.4.
The team found that the samples stored at 4 °C showed lower degradation than the samples stored at 25 °C for all the tested carrier agents, while, under the conditions evaluated, samples encapsulated with the maltodextrin/arabic gum mixture had the lowest k values, suggesting higher encapsulation efficiency and thus greater anthocyanin protection.
The higher efficiency of the carrier agent arabic gum may be related to its structure, they noted.
“Arabic gum is a highly branched heteropolymer of sugars, containing a small amount of protein covalently linked to the carbohydrate chain, acting as an excellent film-forming agent and thus better trapping the encapsulated molecule. This makes the flavylium cation less vulnerable to nucleophilic attack by water molecules, increasing the stability of the anthocyanins,” concluded the authors.
Source: International Journal of Food Science and Technology
Published online ahead of print: DOI: 10.1111/j.1365-2621.2010.02486.x
Title:Anthocyanins: optimisation of extraction from Cabernet Sauvignon grapes, microcapsulation and stability in soft drink
Authors: V. M Burin, P. N. Rossa, N. E. Ferreira-Lima, M. C.R. Hillmann, M.T. Boirdignon-Luiz
