Protection of fish oil from oxidation by microencapsulation using freeze-drying techniques

(N-3)-Polyunsaturated fatty acids (PUFAs) reduce the risk of coronary heart disease. Cold sea water plankton and plankton-consuming fish are known sources of (n-3)-PUFAs. Enriching normal food components with fish oil is a tool for increasing the intake of (n-3)-PUFAs. Due to the high sensitivity of fish oil with respect to oxidation, it has to be protected from oxygen and light. The investigations presented demonstrate the microencapsulation of fish oil using freeze-drying techniques. Emulsions containing 10% fish oil, 10% sodium caseinate, 10% carbohydrate and 70% water were frozen using different freezing techniques and subsequently freeze-dried. Several parameters regarding formulation and process (addition of antioxidants to the fish oil, use of carbohydrates, homogenisation and freezing conditions, initial freeze-drying temperature, grinding) were varied to evaluate their influence on the oxidative stability of dried microencapsulated fish oil. The shelf life of the produced samples was determined by measuring the development of volatile oxidation products vs. storage time. It could be shown that the addition of antioxidants to fish oil was necessary to produce dried microencapsulated fish oil with an adequate shelf life. The best shelf life was achieved for the dried product which was frozen with a slow freezing rate.