1. Separate the egg whites and yolks. Whisk the egg yolk, salt, 10g fine sugar, milk, and salad oil evenly, sift into low-gluten flour, mix into egg yolk paste, and set aside.
2. Use an electric whisk to break up the egg whites, add lemon juice, add 60 grams of sugar in 3 times, and beat to the point of wet foaming (nine times), that is: the egg white peaks on the whisk are long and not stand upright, inside the basin The protein can be curved and pointed.
3. Take 1/3 of the egg white and mix with the egg yolk paste, and stir evenly with a rubber spatula.
4. Pour the mixed batter into the remaining 2/3 of the egg white paste, cut and stir until the egg white and egg yolk paste are completely fused.
5. Take a 10-inch square baking pan, put oil paper on the bottom of the baking pan, pour the cake batter into the baking pan, smooth the cake batter with a spatula, slap the bakeware on the chopping board several times to remove large bubbles. Preheat the oven to 130 degrees (the specific time required depends on the temperature of your own oven), the middle and lower floors, the upper and lower fire, and bake for 30 minutes.
6. Take out the baking pan from the oven, hold the greased paper on both sides with both hands, take the cake out of the baking tray, place it on the cooling net, carefully peel off the greased paper around, place a piece of greased paper on the other cold net, and buckle the cake upside down on the new greased paper And remove the original greased paper.
7. At the beginning of the cake roll, use a knife to cut 3-4 lines that are not to the bottom, so that the center is not easy to crack when rolling, and evenly spread the purple sweet potato coconut filling on the surface of the cake.
8. Roll the cake with a rolling pin and roll the oil paper, and set the shape for 10 minutes after it is rolled.
9. Cut into sections and eat.
Tips:1. The egg white can only be sent to the level of wet foaming. If it is sent to dry foaming, the protein structure is fine and easy to break when rolled.
2. The baking time and temperature should be set according to your own oven.
3. When making cake rolls, the cake crust often sticks to the greased paper, which affects the appearance. Therefore, move the baking pan to the top layer for about 1-2 minutes before baking to make the crust stronger, but not too long. Avoid surface cracking when rolled up.
