When I first started my journey in the Sake brewing world I noticed terms like, "Polished Rice, Husked, Germ, Bran, Fats, and Proteins". It sounded like I was trying to make a cereal instead of a fermented drink. When I went down the rabbit hole of just how rice is polished for Sake I found much more than I had expected.
Before we get to how rice is polished we have to start at the beginning. Initially, people were banging rice with the end of a long wooden pole in a stone bucket, then pouring it into a woven basket. The rice would then be tossed into the air and caught again into the basket using the air around it to blow away the husks. Since then the process has basically stayed the same but was tweaked to become more efficient with a machine instead.
First, A bit of history. The invention of the rice husker came from Brazil in 1885. It was created by a German Brazilian engineer named Evaristo Conrado Engelberg, he called it the Engelberg huller. It was given a British patent and was initially manufactured & distributed out of New York. The machine was not only used for rice, but for coffee beans and other shelled products. The product became so popular that the manufacturing facility had to expand to a larger area.
Husking is the first part of the process to which all rice has to go through before it becomes a part of the Sake brewing process. Husking today is done with a rice husking machine that has the same priciples as the original design. Rice is put into a funnel sitting on top of rollers that have a very small space between them. The outer layer is cracked as it goes between the rollers in a machine. Air is blown in to get rid of the lighter husk, vibrating grated shelves at the bottom help separate the stubborn cracked husks, field junk, and foreign objects from the internal bran covered white rice called the "Endosperm".
Getting back to the polishing of rice. After the rice is de-husked, it's weighed and put into the process of polishing. This process is fairly simple.
One popular practice of rice polishing is placing the rice between a horizontal roller and a grated tube. The roller has leather straps attached to it facing outward touching the grated exterior tube that has very tiny openings. The space between the roller and the exterior tube is very small as the leather straps touch the exterior metal grating. the roller starts to spin as the rice slides around the tube using friction to polish. After a period of time, the rice is given a percentage of polish compared to when it first went into the machine. The percentage number Sake brewers use is the amount of rice that is left AFTER polishing.
70% polished rice is the commercial industry standard for Sake. Most rice you get without paying large amounts of money will be a 90% polished white rice though. Remember, a good Sake is created because of many factors, not just how polished the rice is.
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