Alginate encapsulation could expand probiotic applications

The gelatin microspheres were found to protect the health-promoting bacteria in simulated gastric (stomach) and intestinal juices, and led to the recovery of 13 and 16 per cent more viable cells than observed for the non-encapsulated control, report the researchers from Dalhousie University in Canada.

"This study presents a novel microencapsulation method, which protects probiotic bifidobacteria during exposure to adverse environmental conditions," wrote the authors in the journal Food Research International.

Most foods containing probiotic bacteria are found in the refrigerated section of supermarkets as the bacteria is destroyed by heat and other processing conditions.

This has given the dairy sector, already used to handling live bacteria for the manufacture of yoghurt, a major advantage in probiotic foods - probiotic drinking yoghurts are currently the fastest growing dairy product in Europe.

But increasing research has focused on expanding protecting probiotics during processing and expanding the food categories available to prebiotics.

Such an avenue of research has led companies like Cell Biotech from Korea using a dual-coating to protect probiotics against oxygen, acid, moisture and high temperatures for use in emerging new product categories such as breakfast cereals and smoothies.

The new research reports the potential of the alginate-coated gelatin microspheres cross-linked by calcium ions to encapsulate Bifidobacterium adolescentis

15703T.

The researchers report that microcapsules were prepared by cross-linking gelatin microspheres with the non-cytotoxic genipin, and then coating them with alginate cross-linked with calcium.

Exposure of these microspheres to a simulated gastric juice (pH 2) containing pepsin for two hours and then simulated intestinal juices (pH 7.4) for four hours resulted in significantly higher survival numbers compared to uncoated gelatin microspheres and free cells: 7.6 versus 6.7 and 6.4 log colony forming units (cfu) per millilitre, respectively.

"The novel encapsulation matrix developed in this study was designed to increase numbers of probiotic bacteria surviving the upper segment of the gastro-intestinal tract (GIT) allowing for introduction into the colon where they may offer health benefits by effecting positive changes to the host's immune defence and intestinal microflora," wrote the researchers.

"Future work will look at the development of specific food applications and methods for long-term preservation of the alginate-coated gelatin microspheres," they concluded.

The study was funded by the Advanced Foods and Materials Network (AFMNet), a Network Centre of Excellence, Canada.

Source: Food Research International (Elsevier) Published on-line ahead of print, doi:10.1016/j.foodres.2007.11.001

"Encapsulation in alginate-coated gelatin microspheres improves survival of the probiotic Bifidobacterium adolescentis 15703T during exposure to simulated gastro-intestinal conditions" Authors: N.T. Annan, A.D. Borza, L. Truelstrup Hansen