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Aubergine peel promises provision of natural purples

By Nathan Gray+

09-Oct-2012

Could aubergines provide natural purple colours?
Could aubergines provide natural purple colours?

Anythocyanins extracted from aubergines peels could provide a ready source of stable natural colours for the food industry, suggest researchers.

The study – published in LWT - Food Science and Technology – suggests that extractions of anthocyanins from peels of aubergines (Solanum melongena L. otherwise known as eggplant) using food grade solvents and extraction methods could yield natural colour extracts that are suitable for a range of food and beverage applications.

Led by Paramita Bhattacharjee of Jadavpur University, India, the research team explored the stability and potential food applications of anthocyanins extracted from eggplant peels using either food grade solvent or supercritical carbon dioxide (SC-CO2).

“Our investigation envisages designing extraction procedures using suitable food grade reagents for improved recovery of anthocyanins from eggplant peels for food applications,” explained the researchers.

The solvent extracted colour being more stable at high temperature regimes was suitable for thermal food applications while the SC-CO2 extracted colour is recommended for non-thermal food applications owing to its higher stability and lower metal contamination,” they revealed.

Study details

Bhattacharjee and her team revealed that the highest yield of anthocyanin was obtained at 60 °C with water-ethanol (1:1) in 10% citric acid; whereas, maximum yield of the same under SC-CO2 conditions were obtained with 10 g of citric acid pre-treated peels at 60 °C, 10 MPa with 1.5 h extraction time at a flow rate of 0.2 L min−1 of CO2.

“These methods of extraction of eggplant peel colour are reported for the first time,” they noted.

The team ‘tentatively identified’ delphinidin-3-glucoside and delphinidin-3-rutinoside as the major anthocyanins in the extracts.

Further stability studies revealed that the solvent extracted colour was more stable than the colour obtained via supercritical extraction at high temperature regimes. However, they noted that the trace metal content in the SC-CO2 extracted colour was significantly lower.

The authors concluded that use of the SC-CO2 extracted colour is recommended for all food and non-food applications that do not require high thermal processing, while the solvent extracted colour was most useful for food applications that required higher heat resistance.

Source: LWT - Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2012.09.012
“Solvent and supercritical carbon dioxide extraction of color from egg plants: Characterization and food applications”
Authors: Dipan Chatterjee, Nikhil T. Jadhav, Paramita Bhattacharjee

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