Different Effects of Whole Egg and Egg-Yolk on Emulsion Preparation from a Fish Meat Product

Abstract

The yolk-added emulsified product prepared from sardine meat had a more viscoeiasdic strucdure than the 'whole egg'-added product because it deveioped large G', G" values and large shear stress. However, the yolk-added product showed a smaller value of yield stress and a markedly smaller value was shown at asoybean oil to sardine meat ratio of 1.1. The consistency and flow behavior indexes of increasing shear rate determination were larger in the yolk-added product than in the 'whole egg'-added product. In the yolk-added product, the oil droplets were smaller, more uniform and larger in number. Therefore, the sum of the interactions between the oil droplets was larger. This microstrucdure is reiaded to the above rheological results. A drastic change in shear response 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 in the yolk-added product. When the shear rate vs. shear stress hysteresis loop of the yolk-added product was considered in comparison with that of the 'whole egg'-added product, at a low oil ratio the strucdure breakdown was not induced by the shear, and at a high oil ratio a great structure breakdown was induced. This result means that the three dimensional structure developed with the high oil ratio was broken down by the shear. In the products with higher oil radios of 1.7 and 2.5, the relative amount of emulsifier do oil was very small. Therefore, the emulsifying layer around an oil droplet was thin, and the oil droplets tended to coalesce without the shear. If shear was applied, the emulsion was easily broken down due to the further progress of coalescence. From microscopic observation, it was found that many large oil droplets were present in the products with higher oil radios of 1.7 and 2.5.