Whey protein gel particles - the future of probiotic encapsulation?
offer protection during processing and storage, as well as
extending the food applications of the bacteria to biscuits,
vegetable and frozen cranberry juice, indicates research from
Canada.
"The WPI gel has the potential to increase the survival rate of the microorganism to food processes and during storage and could be used to add probiotic cultures in a wide range of functional food applications," wrote lead author A. Ainsley Reid.
Scientists from Laval University and the Food Research and Development Center Agriculture and Agri-food Canada investigated the protecting effect of microencapsulation of Lactobacillus rhamnosus R011 in semisweet biscuits, vegetable juice and a frozen cranberry juice.
Co-author of the study, Claude Champagne told NutraIngredients.com that the protein-based technique can provide an alternative to microencapsulation (ME) with alginate-type gels or spray-coating with fats, the two most widely-used probiotic encapsulation methods.
"It can be expected that the protein matrix would have different cell release properties than the other ME methods (polymer or fat based)," said Champagne. "Thus, applications can extend to other foods for protection during processing as well as stability during storage but also in nutraceuticals for protection and cell release in the GI tract.
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, led by Jean-Christophe Vuillemard and published in the Journal of Food Science, reports the potential of the L. rhamnosus strain (Inst. Rosell Inc.), encapsulated in a whey protein isolate (WPI, Darisco Intl.). Beads were prepared by extruding the denatured WPI-concentrated bacteria solution, and 96 per cent of the probiotic cells were in the whey protein particles.
The beads were subsequently put into a solution of skim milk powder (20 per cent), sucrose (5 per cent) and bacto casitone (1 per cent), freeze-dried, sieved to produce a powder, and finally vacuum packed.
In order to obtain a bacteria population of 10 million cells per gram, the researchers added 1.1 per cent weight for weight to the foods.
The researchers prepared semisweet biscuits using the microencapsulated probiotic, and also compared the viability of the bacteria in refrigerated vegetable juice and a frozen cranberry juice.
"Microentrapment protected the cells during the production of the biscuit, since 77 per cent of the population of the ME culture remained viable in the fresh biscuit dough as compared to 4.5 per cent for free cells in WPI-based matrix," wrote Reid and co-workers.
However, the researchers report that only four per cent of the ME cells were viable in the biscuits after 24 hours storage at 23 degrees.
"This is the first report on the addition of ME probiotics to biscuits, and further studies are needed to ascertain to what degree microentrapment or pH promoted the survival of the cells in the biscuits," they said.
The researchers also state that theirs is the first report of viability levels in frozen cranberry juice. Similar drops in viability of the cells was observed, as with the biscuits, despite the encapsulated cells having higher survival than free cells. The drop in the cell population in the cranberry juice was most likely due to the acidity of the juice (pH 2.3) and the freezing process, they said.
More encouraging results were obtained when the entrapped probiotics were added to vegetable juice, said the researchers, with 33.4 per cent of the cells still viable after a two-week storage period, compared to only 6.6 per cent of non-encapsulated cells.
"Our findings highlight that vegetable juice could be used as a vehicle for delivering L. rhamnosus cells to the consumers since milk-based free and ME cells maintained high viability after a two-week storage period," they wrote.
Talking to this website, Champagne said this is not the first publication using this technique, but since their initial publication in 2005 (Journal of Microencapsulation, Vol. 22, No. 6, pp. 603-619) other groups have started to explore the potential possibilities.
"We were the first to apply the technique to probiotics and it has subsequently been picked up. Please note that we did not invent the whey gelation process, but we were the first to apply it to probiotics," he said.
Champagne revealed that no industrial partner is yet on-board for this particular process, but research is on-going in this area.
"This technology not only has benefits for use in foods or controlled release in the GI tract. It has benefits for the producers of probiotics as well. The cultures are currently stabilized by freeze-drying prior to shipment to users. However, these particles can be air-dried, which opens the industry to a much less expensive drying process," he said. "We are currently exploring this technology."
Source: Journal of Food Science Volume 72, Number 1, Pages M31-M37; doi: 10.1111/j.1750-3841.2006.00222.x "Survival in food systems of Lactobacillus rhamnosus R011 microentrapped in whey protein gel particles" Authors: A. Ainsley Reid, C.P. Champagne, N. Gardner, P. Fustier, J.C. Vuillemard
