A few months ago, I tried spherification for the first time using sodium alginate mixed with juice, which I slowly dropped into a calcium chloride solution to form tiny, springy, bright orange caviar. It was a tricky process because molecular cooking requires exact ratios and measurements by weight—and any mistakes or miscalculations can result in an end product that is totally unusable. For example, the first time I made this caviar, pictured above, the kombucha-agar solution was slightly too warm and all of the caviar melted together, producing one big blob. For this reason, I find molecular cooking to be a huge challenge, but one that is also the most rewarding at the end if done correctly. This experiment (eventually) yielded a very subtly sweet faux caviar that went well with the saltiness of soy sauce, but the texture here was the most prominent feature—these were silky, soft and smooth and complimented the texture of the rice perfectly. Method adapted from Introduction to Molecular Gastronomy insert included in Molecular Tools by Molecule-R Flavors.
for the sushi
1/2 cup sushi rice, soaked for 30 minutes then rinsed well
1 cup water
1/2 TB rice vinegar
1/2 TB sugar
1/4 TB salt
for the caviar
1/2 cup Kombucha Gingerade
2 grams agar powder
enough vegetable oil to fill a tall beer glass
Place the rice and water into a rice cooker. While it cooks and steams, combine the sugar, vinegar and salt in a separate glass bowl. Set aside.Pour the oil into a tall beer glass, so it is filled 3/4 full. Place in the freezer to chill for 30-45 minutes. 10 minutes before you take the glass out of the freezer, combine the kombucha and agar in a small saucepan. Whisk until combined and bring to a small boil. Transfer to a bowl and let it cool slightly, until it’s slightly warmer than room temperature.
Fill a pipette or squeeze bottle with the kombucha and slowly drop it into the very cold oil. The reason you use a tall glass is so it gives the kombucha a few seconds to firmly gel before it hits the bottom of the glass.To remove the caviar from the oil, pour it over a fine mesh strainer and store the oil to reuse in another application later (this should not affect the taste of the oil). The caviar will be quite sturdy if done properly. Rinse with a little cold water and set aside.
Cut the nori sheets into 1 to 1 1/2 inch ribbons. Set aside.When you are ready to assemble the sushi, place the cooked rice into the glass bowl and combine. Run your hands under some water before handling the rice. Shape the rice into small oval shapes, about the size of your thumb. Then wrap one of the nori strips around that, securing the end with a little bit of water to seal it. Spoon some of the kombucha caviar on the top. Serve with soy sauce.