This study was conducted to investigate the quality characteristics of cookies prepared using skate powder (0, 1, 3, 5, 7%) as a substitute for flour. The pH of the cookie dough decreased significantly in response to the addition of all levels of skate powder. However, there were no significant differences in the dough values among the test groups. Furthermore, when the spread factor values were compared among groups, they were found to be inversely proportional to the skate powder concentration. In addition, the Hunter's color L, a and b values decreased significantly as the level of skate powder increased. Moreover, the addition of 1-7% skate powder resulted in increased hardness, cohesiveness, springiness, and brittleness when compared to the control. Finally, the results of the sensory evaluation and acceptance test showed that the cookies containing 3% skate powder had the highest scores.

Physicochemical and functional properties of collage from skate skin (Raja Kenojei) are examined depending on pH and NaCl concentration in the medium. The solubility decreased as NaCl concentration increased but, turbidity increased as concentration of collagen increased. Oil-holding capacity and water-holding capacity were similar to other fish skin collagens. Emulsion activity, creaming stability, and viscosity were lowest at where pH levels were isoelectric point regions of collagens. However, the higher pH values at 7.0-9.0 caused increasing foam expansion, foam viscosity, and gel strength. These results indicated that collagen from skate skin could be used as a functional ingredient for food and industrial applications.