RICE WAS INTRODUCED to Japan in approximately 100 BCE, and, soon thereafter, the Japanese were makin' sake. By 689 C.E. the process was sufficiently advanced to warrant the establishment of a brewing department in the imperial palace. To give you an idea of how long sake has been around, the Japanese weathered their experiment with prohibition in 1264 C.E., during the upheaval surrounding the repeated invasions of Kublai Khan's Mongol hordes. Over the course of the intervening millennia, sake has become a part of daily life and serves as the drink of ritual, ceremony, and celebration.

While sake is, like beer, grain based, its flavor, alcohol content, and cost structure are much more closely aligned with the world of wine. What matters most, however, is that it's made of rice. There are approximately 65 varieties of rice used in the production of sake, each with its own characteristics; as with wine grapes, certain varieties are more prized than others and are native to particular regions.

One of the surest gauges of a sake's quality is the level to which the rice has been "polished." To polish the rice, the individual grains are milled down, the outer layers of the grain shaved away to remove elements that hamper the fermentation process and/or lead to off flavors or undesirable coloring in the final brew. Table rice is also milled but only to about 91 percent (i.e., only 9 percent of the grain's outer husk is shaved away). Rice in the finest sake can be polished to less than 40 percent (more than 60 percent of the husk removed) to expose the purest heart of the grain.

Unlike grapes, rice grains have no natural sugars to activate the yeast to begin the fermentation process. Koji, a term that refers to a category of several mold strains, must be grown on the rice to act as the catalyst that changes starch into sugar and, eventually, alcohol.

With more than 1,500 sake breweries producing roughly 10,000 different kinds in Japan alone, there is a truly massive range to choose from. For this reason, grades of sake are broken down according to the level to which the rice used in its brewing has been polished. The best varieties are known as "special designation" sakes; these constitute less than 20 percent of overall sake production. In that top 20 percent, you'll see a number of the same terms used. Here's a rudimentary list of how sake is graded, from premium to über-premium:

Honjozo Polished to 70 percent or less with added alcohol. The grade of premium sake that would most likely be served warm (not hot!). Adding alcohol is not a method of "cutting" sake as a cost-saving measure but a carefully prescribed technique used to even out flavors and enhance the aroma of certain sakes. Honjozo tends to taste a bit lighter than some of the other premium varieties.

Junmai Polished to 70 percent or less. The grade for purists. Shortened from junmai-shu, junmai means "pure rice sake" ("shu" is used as a suffix and simply means "sake"). Though polished to the same level as honjozo, the term junmai can only be used to refer to sake made without any added alcohol and with no additional sugars or starches beyond the initial rice used in the brewing process.

Ginjo Polished to 60 percent or less. The term ginjo (GIN-joe) designates the highest grade of sake. Thanks to choice ingredients, more painstaking brewing techniques, and colder fermentation temperatures, these sakes tend to project a bit more personality than some of their less highly crafted counterparts.

Daiginjo Polished to 50 percent or less. Daiginjo, or "great ginjo," is the best of the best. Made with the most highly polished, highest-quality rice, it is held as being representative of the best the craft can offer. It is the rarest and, consequently, the most expensive.

The term junmai may also be used as a compound term to refer to ginjo and daiginjo sake that is also pure rice sake. So, for example, you can have just junmai, just ginjo, just daiginjo, or junmai ginjo and junmai daiginjo. If not specifically labeled junmai, alcohol has been added to ginjo and daiginjo sake according to the strictures dictated in the adding of alcohol to honjozo varieties.

Relatively low demand, small batch production, and the difficulties associated with transporting, storing, and refrigerating quality sake means the best stuff hasn't made its way to the States in any great volume. But that is beginning to change. The Bay Area is home to some of the largest domestic producers and importers of sake in the country. In the next column I'll profile some local sake producers, shops where you can buy premium sake, and places to go tasting. Get yer boots on, we're goin' drinkin'....