Effect of Yolk/White Ratio on Flow Property and Droplet Size in Fish Meat Emulsion

Fish meat emulsion was prepared from very-low-lipid sardine minced meat obtained through grinding or suspending in weak alkaline solution, and the effect of the yolk/white ratio in a blended emulsifier on this emulsion was investigated using rheometry and microscopy. A blended egg yolk/egg white ratio of 0.233/0.466 was equal to a constituent ratio in the real whole egg. Four changes in flow property, reported when whole egg was used as an emulsifier instead of egg yolk, were reproduced in ground-meat emulsion with a blended emulsifier: (1) the decrease in the flow behavior index in the up-curve (2) the increase in the yield stress in the up-curve (3) the decrease in the consistency index in the down-curve and (4) the increase in the hysteresis loop area. In suspended-meat emulsion, (2) and (4) became obviously true at the yolk/white ratios of 0.1/0.6 and 0.0/0.7. Lower moisture in suspended meat, which was prepared from sardines chilled in ice-water for a slightly longer period, would be the main reason for the result that these two items were not reproduced at the ratio of 0.233/0.466. The effect of the egg-white portion worked well under the higher moisture conditions of the suspended meat due to more egg-white. The increase in oil droplet size by the effects of both yolk and white caused the deformation of the droplet shape and the resulting coalescence during the shear. As a result, the shear-thinning property was intensified. The thread-like substances and the myofibrillar network structure tightly adhered to the surface of the droplet during the shear and promoted the coalescence at the yolk/white ratio of 0.0/0.7.