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Stable betalain extracts offer yellow pigment possibility: Study

By Nathan Gray , 12-Oct-2010

New research has identified a procedure to create what is claimed to be the first stable natural yellow pigment extracted from betalains.

According to findings published in the Journal of Agricultural Food Chemistry, a spray-drying procedure for the encapsulation of indicaxanthin an – until now – unstable yellow betaxanthin pigment. Encapsulation of indicaxanthin with maltodextrin was found to produce a stable bright yellow powder containing a single pigment.

“This paper demonstrates the high degree of stability achievable for betalains under encapsulation … It constitutes the first case of a pure encapsulated betalain, so providing a yellow colorant,” wrote the researchers, led by Dr Fernando Gandia-Herrero, at the Universidad de Murcia, Spain.

“The stabilization of pure betalain pigments may boost the use of these natural bioactive and colouring molecules in the food industry and promote their application in the pharmaceutical and cosmetic areas,” added the authors

Naturally unstable

Betalains are natural, water-soluble pigments that are of growing interest in the food industry. They give bright colour to many types of plants and flowers, but can also be obtained from edible sources like beetroot and cactus pear.

In recent years, evidence has amassed to support the health-promoting potential of betalain-containing foods, particularly cactus pears. They have been marketed as powerful antioxidants, and have also been suggested to inhibit the peroxidation of linoleic acid and the oxidation of LDL.

Present in many plants belonging to the Caryophyllales order, betalains are split into two groups: red-violet betacyanins, and yellow betaxanthins.

Betanin is the best-known betalain – the betacyanins is the main red pigment found in red beetroots, and is the main colouring component present in the E-162 food colour additive.

Indicaxanthin is a common betaxanthin, and is responsible for yellow and orange shades in many fruits and flowers. However, the authors noted that due to stability concerns, no attempts have been made to encapsulate or obtain yellow colorants based on betaxanthins such as indicaxanthin.

The new study aimed to improve the stability of indicaxanthin through extraction and encapsulation in a maltodextrin matrix. The stability of the encapsulated pigment was then analyzed under different conditions.

Encapsulation

Spray drying of indicaxanthin was carried out using 20 per cent maltodextrin, the optimal inlet temperature for spray drying was considered 140 °C, and a bright yellow powder was obtained, stated the authors.

The stability of the encapsulated yellow pigment was then analyzed under different conditions.

Pigment stability was reported to be lower at pH values of 4, 5, and 8, with more stable pigments at pH 6 and 7.

The presence of light decreased the stability of the betaxanthin significantly at all pH values.

In the presence of light the researchers also observed the lightness of the powders to increase, whilst the chroma of the powders decreased. However, the colour parameters were not altered after storage for the same period in the absence of light

“In the absence of light, pure encapsulated pigment can be stored at 20 °C for months without appreciable loss of the bioactive substance and colour variation,” stated the authors.

Added stability

The researchers concluded that their results confirm it is possible to produce highly stabile yellow powders from betalains, under certain conditions.

“These data show that the encapsulation of indicaxanthin in a maltodextrin matrix greatly improves the stability of this pigment,” stated the authors.

“The stabilization of pure betalain pigments may boost the use of these bioactive and natural colouring molecules,” they added

Sources: Journal of Agricultural Food Chemistry
Published online ahead of print, doi: 10.1021/jf101695f
“Stabilization of the Bioactive Pigment of Opuntia Fruits through Maltodextrin Encapsulation”
Authors: F. Gandia-Herrero, M. Jimenez-Atienzar, J. Cabanes, F. Garcia-Carmona, J. Escribano

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