Yeast Microcapsules Overview

Microcapsule refers to a kind of miniature container or package with a wall, which can encapsulate solids, liquids or gases, and can improve the stability, solubility or processing performance of the core material.In the 1970s, some researchers invented the technology of using microbial cells as the natural wall material for the preparation of microcapsules.

Yeast is a very common microorganism used in food, from a wide range of sources, its cells are spherical or oval, in a dispersed single-cell state, the size of a few micrometers to 20 micrometers in the range of the intact cell wall and the cell membrane has a certain degree of strength and permeability, so it is the ideal microcapsule wall material.

And yeast microcapsules do not need to introduce other chemical reagents in the preparation process, there is no problem of organic solvent residue or removal, so it is very suitable for food additives embedded.

Yeast microcapsules in food applications

At present, yeast microcapsules due to its good properties and the wide range of sources make its application in food more and more widely, the following will be briefly introduced.

1. Application in oils and fats
Edible fats and oils, spice oils, etc. are very widely used additives in food, especially in flavorings and preservatives, such as spice oil is mostly composed of volatile components, unstable in nature and poor solubility, which can be made into microcapsules to improve its stability, solubility and broaden its application.

For example, Wang Jinyu et al. used dry brewer’s yeast as the wall material to prepare clove oil microcapsules, optimized the selection of embedding conditions, and obtained a microcapsule product with an embedding rate of 41.26%, and through the bacteriostatic experimental research, the yeast microcapsules of clove oil have a certain slow-release bacteriostatic effect.

Yeast cells such as brewer’s yeast as the wall material, fatty acids as the core material to prepare microencapsulated products, fatty acids can be selected from linoleic acid, γ-linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), etc., through microencapsulation can improve the dispersion of fatty acids.

2. Application in coloring
Natural pigments are natural in color, safe for consumption, and have certain nutritional and health effects, which are favored by many food enterprises. However, many pigment for oil-soluble, and stability is poor, especially natural pigment to light, heat, oxygen that acid and alkali is very sensitive, easy to cause fading or discoloration, through microencapsulation can improve the solubility of pigment and stability.

Mature gardenia fruit contains rich gardenia yellow pigment, gardenia yellow pigment in the saffronin and saffron acid to protein, starch content rich material has good coloring ability, and has certain nutritional value and health care function.

Adopting yeast cells as wall material to embed gardenia yellow pigment, can get the microcapsule product with embedding rate of 40～70%. This technology can improve the stability of gardenia yellow pigment, strong coloring to protein and so on, can control the release of pigment, make it uniform coloring. Lutein is insoluble in water, slightly soluble in oil, unstable, very easy to oxidize, heating, light and so on will make it oxidize and lose activity.

Yeast cells as the wall material for lutein microencapsulation, can be obtained 60% ~ 85% embedding rate of lutein microencapsulation products, can realize the slow release of lutein.

3. Application in nutritional additives
The nutrients used for microencapsulation can play a role in improving the stability, control the role of the release, such as plant extracts, flavonoids, polyphenols and other substances, after microencapsulation can expand its application in the food industry.

Such as okra flavonoids biological activity is not stable, the use of yeast cells as the wall material, its embedding treatment, can improve its biological stability. Prickly pear fruit is rich in vitamin C, but its application is limited by its unstable nature.

Taking permeable yeast cells as the wall material of microcapsules and prickly pear juice as the core material, both of them were embedded by high-frequency contact, and then whey protein was used to encapsulate the outer layer, so that prickly pear VC microcapsules, which are rich in VC and polyphenols and other active ingredients, stable in nature and with good slow-release performance, could be prepared.

Yeast cells from a wide range of sources, safe for consumption, a good source of wall materials, the current research on yeast microgels is also gradually increasing, the application in food will be more and more extensive, the development of more abundant yeast microcapsules products, improve the quality of yeast microcapsules will also be the focus of future research.
References: Liu Ziqin, Application of yeast microcapsules in foodstuffs.