However, the microstructure of batches manufactured with fish oil (Fig. 3C and D) was very different to those of control batches (Fig. 3A and B). The micrographs showed a more continuous and compact structure in both cases. The difference of these batches in relation to the con- trol ones is due to the presence of the pre-emulsion and probably to the caseinates. These milk proteins have important emulsifier properties and can link fats directly and strongly and, consequently, binding of the fish oil with the remaining components of the meat emulsion. The result is a more compact matrix that confers a greater consistency to the product and promotes textural changes, mainly the greater hardness and mastication work observed in 6% of the batches (Tables 4 and 5). The relationship between the texture and the consistency of the matrix has been pre- viously observed by Ca ́ceres et al. (2006) in functional cooked sausages manufactured with calcium salts.