Wanwimol Klaypradit and Yao-Wen Huang from the University of Georgia's Department of Food Science and Technology report that combining chitosan and maltodextrin and applying the ultrasonic technique produced the smallest particles with highest emulsion stability, with high retention of the omega-3 fatty acids EPA and DHA.
"The EPA and DHA content (240 mg/g) of the encapsulated powder were slightly higher than commercial specification (100 mg/g) and they had low moisture content and water activity, acceptable appearance and encapsulation efficiency," they wrote in the journal LWT- Food Science and Technology .
"The ultrasonic technology used in this study could lead to application in the food industry improving the stability of tuna and other oils," they added.
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.
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.
According to background information in the article, chitosan is already used as a wall material for encapsulation of sensitive bioactives like lipophilic drugs, vitamin D2, astaxanthin, and olive oil extract.
Klaypradit and Huang state however that little is known on the microencapsulation of fish oils using chitosan, with the omega-3 rich oils usually encapsulated in various caseinates, celluloses, or dextrins.
The research also explores the potential of an ultrasonic atomizer for the encapsulation process, as an alternative to spray-drying.
"Spray-drying [has] the disadvantage that the high temperature used during the drying process accelerates the oxidation of oils," they wrote.
The encapsulation technique used in the new study used three steps - emulsification, ultrasonic atomisation, and freeze drying.
Combining the chitosan with maltodextrin or whey protein isolate, the researchers investigated the encapsulation of tuna fish oil.
They report that the optimum ratios for chitosan to maltodextrin or whey protein were 1:10 and 1:1, respectively, with the former combination producing the smallest particle size (8.4 versus 10.2 micrometres, respectively), and the highest encapsulation efficiency (83.5 versus 79.3 per cent, respectively).
The combination of chitosan and maltodextrin also produced a white emulsion, while the whey protein combination produced a less desirable off-white emulsion.
"This study demonstrated that ultrasonic atomizer was the promising alternative method for tuna oil encapsulation," concluded the researchers.
"The encapsulated powder made from both stable emulsion formulations contains high EPA and DHA content, low moisture content, acceptable colour and encapsulation efficiency."
The researchers note that the research is ongoing, stating that the effects of ingredients used as wall materials for encapsulation on the oxidation of tuna oil needs to be studied, along with whether the chitosan microcapsules are affected by product formulation.
Source: LWT - Food Science and Technology (Elsevier) Published online ahead of print, doi: 10.1016/j.lwt.2007.06.014 "Fish oil encapsulation with chitosan using ultrasonic atomizer" Authors: W. Klaypradit and Y.-W. Huang