National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa, 236-8648, Japan
An attempt was made to produce frozen surimi containing large amounts of highly unsaturated fatty acids such as EPA and DHA. Fish oil was emulsified with walleye pollock surimi by agitation using a vacuum high-speed rotating mixer, and the best condition for the preparation of a stable emulsion was investigated by measuring the size of oil droplets, the viscosity, and the gel-forming ability of the emulsified product.
The results were as follows: when agitated at relatively low speed, the size of oil droplets tended to decrease and gel-forming ability increased in relation with the progress of agitation. However, the degree of emulsification did not reach a constant level even when the agitation was prolonged for more than 10min (900rpm). On the other hand, when agitated vigorously with stepwise increase of the mixing speed (300-3,000rpm), the viscosity of the emulsified product quickly increased to a higher level, and its heat-induced gel forming ability was improved and the oil droplets in it became a uniformly fine size.
These results indicate that vigorous agitation of surimi with fish oil is necessary to enable the heat-induced gelation of its emulsified product to achieve good quality, through the formation of fine oil droplets in it.