Chitosan microcapsules get bioavailability boost

Researchers from the University of Massachusetts report that while chitosan has previously been proposed as an effective encapsulating ingredient due to its improved stability to thermal processing, lipid oxidation, and freezing and thawing, the actual bioavailability of the encapsulated lipid was not clear.

The researchers, led by Yeonhwa Park, report in the journal Food Chemistry​ that the excellent stability of the chitosan capsules does not affect the bioavailability of the encapsulated ingredients, which could be lipids like omega-3s or fat-soluble ingredients like certain vitamins.

"This encapsulating technology can be a very useful tool to provide biologically active lipid and lipid soluble components, such as fish oil. This method can protect stability when applied in a number of food systems without compromised fat bioavailability,"​ wrote Park.

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.

Indeed, with the fear of commodification continuously looming, food manufacturers are turning to microencapsulation technologies as a way of achieving much-needed differentiation and enhancing product value. Tapping into key and emerging consumer trends with innovative techniques is becoming increasingly important for food manufacturers.

Changing consumer trends and tastes are primarily responsible for driving innovation in the microencapsulation market, says market analyst Frost & Sullivan. Since food manufacturers constantly monitor such trends, food ingredients companies are always looking for ways to meet these ever-changing demands, thereby promoting the need for novel microencapsulation technologies.

One such technique could be the chitosan microcapsules. The polysaccharide, derived from shellfish and mostly used as a preservative, is of interest to food formulators because it is said to be one of the few food-grade polymers to have a positive charge across a wide pH range.

Using an electrostatic layer-by-layer deposition method, the researchers coated emulsified soybean oil with lecithin (negatively charged) and then the positively charged chitosan layer. Ninety-five per cent of the resulting particles were said to be less than 10 micrometres.

The bioavailability of the microcapsules was then tested by feeding them to four-week old male mice, and compared to mice eating a control (non-emulsified oil only), the non-emulsified oil plus chitosan (non encapsulated), or the emulsified oil plus chitosan (non encapsulated).

After the mice had eaten these diets for four weeks, the researchers report that no differences were observed between any of the groups, with fat absorption from all diets reports to be at least 90 per cent.

"These results suggest that encapsulation of emulsified lipids by chitosan does not impact their subsequent digestibility, which means that chitosan encapsulation could be useful as a tool to deliver bioactive lipids and lipid soluble compounds without affecting fat absorption,"​ concluded the researchers.

Previous studies have reported that chitosan supplements can reduce cholesterol levels in both animals and humans, an observation that was replicated in the non-emulsified oil plus chitosan (non encapsulated) group of this study. No such effect was observed when the chitosan was used as an encapsulator, said the researchers.

Park and co-workers stressed that human studies need to be performed to confirm these findings. They also said that the taste and processing stabilities need to be determined.

Source: Food Chemistry​ Published on-line ahead of print; doi: 10.1016/j.foodchem.2006.12.020 "Influence of encapsulation of emulsified lipids with chitosan on their in vivo digestibility"​ Authors: G.Y. Park, S. Mun, Y. Park, S. Rhee, E.A. Decker, J. Weiss, D.J. McClements, Y. Park