Effect of calcium chloride on the uniformity of colouring in sushi red ginger slices by modulating the properties of starch.

The colour of sushi red ginger slices without blanching is not uniform, which seriously affects their sensory quality. The effect of calcium chloride (CaCl 2 ) pretreatment on the uniformity of colouring and the properties of ginger starch have been studied. The crystalline region of the starch in blanched ginger slices was broken, which might be beneficial for uniform colouring. The effect of CaCl 2 pretreatment on starch properties depended on the concentration. The influence of CaCl 2 at a concentration higher than 3.5 mol L -1 was more pronounced than that at a lower concentration. The uniformity of colouring was close to the effect of blanching treatment. Furthermore, the starch crystallization was destroyed, the granules were broken, and the polarized cross disappeared, which was consistent with that observed for the starch in blanched ginger slices. Therefore, it is possible to achieve a uniform colour in red ginger slices at room temperature through CaCl 2 pretreatment.