Study On The Protection Of Freshwater Fish Oil By Chitosan Microcapsules

Freshwater fish oil is rich in unsaturated fatty acids and has high nutritional value, so it’s worthy to be developed and applied. However, the high degree of unsaturation that results in the oxidative deterioration of fish oil, the fish odour and its liquid state limit the development of fish oil products. Microencapsulation can provide protection for fish oil while masking its odour and changing its physical form, which makes fish oil easier to apply. A variety of materials can be used as microcapsule wall materials. Chitosan made from shrimp shells is a kind of natural alkalescency polysaccharides with good antibacterial activity, film-forming property and emulsifying ability, so it can be used as an ideal wall material. In this paper, fish oil microcapsules were made with chitosan by spray drying. The protection of fish oil by chitosan microcapsules and the application of fish oil microcapsules were studied. This paper provides a theoretical guidance and technical support for the comprehensive utilization of chitosan and freshwater fish by-products.The freshwater fish oil microcapsules were prepared with chitosan. The preparation technology was investigated. The stability index and particle size of emulsion were used as the evaluating index to confirm the mixture ratio of emulsifiers. The encapsulation efficiency, loading efficiency and particle size of emulsion were used as the main evaluating indexes for studying the effects of preparation conditions, such as chitosan concentration, wall-core ratio, emulsifier content and homogenization pressure. The optimum technological conditions of microencapsulation were determined by orthogonal experiment. The optimum conditions is obtained as follows: 14 for the HLB value of emulsifiers(Tween 80 and Span 80), 1.00%(w/w) for the rate of chitosan; 3:2 for the wall-core ratio; 0.35%(w/w) for the emulsifier content, 35 MPa for the homogenization pressure and 180℃ for the temperature of inlet-air. The encapsulation efficiency of microcapsules made under the optimum conditions was 73.8%.The quality of fish oil microcapsules was evaluated. The protection of fish oil by chitosan microcapsules and the storage stability of product were studied. The product had a good appearance, creamy white, non-fish odour and low moisture content. The particle size distribution was uniform. The oxidation stability of microcapsules was measured by storage experiment. The results showed that the oxidation stability of fish oil is greatly improved after microencapsulation. The oxidation degree of fish oil microcapsules reduced 32.30% compared to fish oil without encapsulated. It meant that the microencapsulation of fish oil can improve the oxidation stability and prolong the shelf life.The storage and application in milk tablets of fish oil microcapsules were studied. In order to solve the oxidation during the preparation process and storage period, the antioxidant was added and the nitrogen was used. It showed that this two methods can effectively reduce the fish oil oxidation during microencapsulation process and storage. Sensory evaluation method was used to confirm the milk tablet formula added fish oil microcapsules. The product had creamy white, good shape, milk flavor and non-fish odour. It was more acceptable compared to the product in the market. The storage experiment results showed that milk tablets added fish oil microcapsules had good taste and color after 60 d storaged at 4℃.