DIFFERENT EFFECTS OF WHOLE EGG AND EGG-YO LK ON EMULSION PREPARATION FROM A FISH MEAT PRODUCT

The yolk-added emulsified product prepared from sardine meat had a mor e viscoelastic structure than the 'whole egg'-added product because it developed large G', G'' values and shear stress. However, the yolk-ad ded product showed a smaller value of yield stress and a markedly smal ler value was shown at a soybean oil to sardine meat ratio of 1.1. The consistency and flow behavior indexes of increasing shear rate determ ination were larger in the yolk-added product than in the 'whole egg'- added product. In the yolk-added product, the oil droplets were smalle r, more uniform and larger in number. Therefore, the sum of the intera ctions between the oil droplets was larger. This microstructure is rel ated to the above rheological results. A drastic change in shear respo nse was found between a soybean oil ratio of 1.1 and 1.7 in both the ' whole egg'-added and the yolk-added products but was more pronounced i n the yolk-added product. When the shear rate vs. shear stress hystere sis loop of the yolk-added product was considered in comparison with t hat of the 'whole egg'-added product, at a low oil ratio the structure breakdown was not induced by the shear, and at a high oil ratio a gre at structure breakdown was induced. This result means that the three d imensional structure developed with the high oil ratio was broken down by the shear. In the products with higher oil ratios of 1.7 and 2.5, the relative amount of emulsifier to oil was very small. Therefore, th e emulsifying layer around an oil droplet was thin, and the oil drople ts tended to coalesce without the shear. If shear was applied, the emu lsion was easily broken down due to the further progress of coalescenc e. From microscopic observation, it was found that many large oil drop lets were present in the products with higher oil ratios of 1.7 and 2. 5.