Writing in Innovative Food Science & Emerging Technologies, the reviewers provide an overview of ‘the most important and new technologies’ used in probiotic encapsulation – noting that most probiotic foods in the current market are refrigerated dairy products, but that large market opportunities may be open to those who can deliver strains in other product categories,
Led by María José Martín from the University of Granada, Spain, the team noted that the main problem associated with incorporating potentially beneficial bacterial strains in to a wider range of food products is the low survival of these microorganisms in the food matrix and in gastrointestinal tract.
“Thus, the protection and isolation of the microorganism from the food matrix and the environmental condition is crucial for the development of new probiotics food,” they said. “Microencapsulation is of great interest since it could allow a wider application of probiotics in the food market.”
The Spanish team noted that aside from the polysaccharides traditionally used as a matrix in microencapsulation, new materials are being tested and new technologies are developed.
However, they suggest that there is still a need to develop new technologies or equipment that produce uniform particles for industrial applications.
“In addition, only a few in-vivo studies have been carried out to test the beneficial effect of encapsulated probiotics,” said the team.
“Although these studies show promising results, they have only been carried out in animals,” they added – noting that large clinical trials using encapsulated forms of probiotics will be ‘mandatory’ to provide evidence of any beneficial health effects such ingredients may have.
José Martín and her colleagues noted that probiotic microorganisms present in any food should survive in significant number (106-108 CFU/g), although the exact number varies from strain to strain.
“It has to be pointed that foods matrices should help probiotics to survive through the gastrointestinal tract and regulate the colonization of the gastrointestinal tract,” they said. “Therefore, selection of suitable food systems to deliver probiotics is a vital factor that should be considered in developing functional probiotic foods.”
Before selecting an encapsulation technology, industry should take in to account, the following points, said the Spanish researchers:
- Which conditions affect probiotics viability?
- Which processing conditions are used during food production or processing?
- What will be the storage conditions of the food product containing the encapsulated prior to consumer use?
- Which particle size and density are needed to incorporate it properly in the food product?
- What are the triggers and mechanisms of release?
- What are the cost constraints?
With these points in mind, they noted that probiotics are affected by different conditions, including moisture content, high temperatures, and agitation.
“In this respect food matrices should be produced in mild conditions, low temperature, controlled agitation, small presence of oxygen and moderate pH,” they said – noting that industry should test the best storage conditions for the particular strains before introducing them into food matrices.
In this respect, they noted that most of the studies are carried out at 4 °C and room temperature.
“Particle size should be enough to protect probiotic but not to cause gritty mouthfeel,” they said – noting that it has been reported that soft, rounded particles are not perceptually gritty up to about 80 μm.
In addition, José Martín and her team said that the amount of particles that should be incorporated will depend on the dose of probiotic required, while the mechanism of release depends on the technology used and the material. The full review (available here) outlines several different technology options including the use of extrusion and emulsion technologies, rennet-gelled protein encapsulation, fluid bed systems, freeze drying, impinging aerosol technology, electrospinning, hybridisation systems and spray drying technologies – such as two step drying, spray chilling and ultrasonic vacuum spray drying
“Finally, the balance between cost and benefit should be taken into account, since some of the technologies described below required specific devices or materials that can increase production cost,” they said. “The extra costs incurred by microencapsulation have to be estimated so that they can be minimized. Cost savings can be derived from easier technologies, lower waste of bacterial material and better health impact of the product."
Source: Innovative Food Science & Emerging Technologies
Published online ahead of print, doi: 10.1016/j.ifset.2014.09.010
“Microencapsulation of bacteria: A review of different technologies and their impact on the probiotic effects”
Authors: María José Martín, et al