One of the pleasures of sitting at the sushi counter is watching the sushi master work on his craft.
He holds the stuffing between the index finger and thumb of his left hand while grasping the ball (rice with vinegar) with his right hand. He gently squeezes the ball and then in a smooth motion moves the stuffing from his left hand to the top of the ball. The whole process of turning a ball of rice into a finished piece of sushi takes less than six seconds. Every movement is precise and purposeful.
However, no matter how many pieces the chef makes one by one, you will never see a grain of rice stick to his hands. If you or I cooked just one piece of sushi, our hands would be covered in rice. So why doesn’t this happen to them? Their hands do not look greased. Perhaps sushi chefs have particularly smooth or dexterous hands compared to ours.
Of course not. It’s actually because of the vinegar.
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Cooks keep a bowl of vinegar nearby, which they constantly moisten their hands with. This procedure is called “Tezu” or water with vinegar, which disinfects the hands and cools their palms. As the vinegar evaporates, it takes the warmth of your hands with it.
Usually hands are heated to 33-34 degrees Celsius (91-93 degrees Fahrenheit), but sushi chefs cool their hands to around 30 degrees Celsius (86 Fahrenheit). This transfers heat from the hands to the ball, preventing it from becoming sticky. In other words, not a single grain of rice sticks to their hands.