Yeast encapsulation to mask bad taste of polyphenols?
the unpleasant flavour and boost stability of water-soluble
antioxidants, says new research.
The Chinese researchers report that a low cost-high volume microencapsulation technique may offer an innovative alternative to expensive lecithin as a means of encapsulating water-soluble ingredients.
"The new yeast-cell-based encapsulation protocol may have some general interests for maintaining the stability of other water-soluble substances," wrote lead author Guorong Shi from the Hunan Agricultural University.
Using yeast as an encapsulation vehicle is not new, and yeast capsules have attracted interest from the food industry since the encapsulation of hydrophobic (water-repelling) flavours or essential oils in empty yeast cells has been reported to be thermally stable at temperatures up to 240 degrees Celsius.
The researchers note encapsulation of water-soluble (hydrophilic) ingredients represents a significant challenge to food formulators using only food-grade wall materials since the encapsulated substances are more susceptible to change. "The wall materials used usually are polymers or expensive lecithin," they said.
"To the best of our knowledge, there are no reports on the microencapsulation of [the water-soluble antioxidant, chlorogenic acid] CGA," added the researchers.
Writing in the Elsevier Journal of Food Engineering, Shi and co-workers focussed on the polyphenol chlorogenic acid, a potent antioxidant present in a range of foods, but most notably coffee. The health benefits of polyphenols continue to generate interest, but polyphenols in general are reported to be relatively unstable and have unpleasant tastes.
The microencapsulated CGA was prepared by simply stirring the yeast, CGA and water together, centrifuging, decanting and ultimately freeze-dried. The encapsulation efficiency (EE), a measure of the concentration of active ingredient encapsulated, was found to be related to the purity of the CGA with 85 per cent CGA resulting in an EE of 6.6 per cent, and 98 per cent CGA purity resulting in an EE of 12.6 per cent.
Storage stability of the CGA microcapsules as a powder were investigated at varying temperatures and humidity, and the researchers report "no chemical changes had taken place during the encapsulation".
In vitro experiments to determine the release profiles the breakdown and release of the active ingredient in a model of the human intestine reportedly showed that more than 95 per cent of chlorogenic acid was released within two hours and complete release was achieved within five hours.
"Therefore, the yeast cells can prevent chlorogenic acid from change without slowing down the release too much," wrote the researchers.
"In summary, we have demonstrated the successful preparation of yeast-encapsulated water-soluble antioxidant, chlorogenic acid, as confirmed by the fluorescence micrographs and FT-IR spectra. Moreover, the same retention time and spectra between the standard and microcapsule suggested that no chemical changes had taken place during the encapsulation processing.
"The yeast encapsulated chlorogenic acid was highly stable under wet and thermal stresses, and the release profiles suggested that the yeast cells could prevent chlorogenic acid from change without slowing down the release too much," said the researchers.
Microcapsules are tiny particles that contain an active agent or core material surrounded by a shell or coating, and are now increasingly being used in food ingredients preparation. The technology can be used to deliver a host of ingredients - flavours, oils, peptides, amino acids, enzymes, acidulants, colours and sweeteners - in a range of food formulations, from functional foods to ice cream.
The technology is attracted growing interest because it can also decrease costs for food makers, particularly those using sensitive ingredients like probiotics, and by reducing the need for preservatives.
Source: Journal of Food Engineering Volume 80, Issue 4, Pages 1060-1067 "Yeast-cell-based microencapsulation of chlorogenic acid as a water-soluble antioxidant" Authors: G. Shi, L. Rao, H. Yu, H. Xiang, G. Pen, S. Long and C. Yang