Sake classification is based on two primary factors: the level to which the rice grain has been polished and whether the sake has been fortified with brewer's alcohol. If a sake is labeled junmai, then no alcohol was added. Another way of stating it is that if one does not see the words junmai on a bottle, it is fortified. The junmai sake group which includes tokubetsu junmai, junmai ginjō, and junmai daiginjō, is in general, richer and denser in style than their fortified counterparts (Honjōzō, tokubetsu honjōzō, ginjō, and daiginjō) and typically not as aromatic.

Milling of the rice grain is done because the outer portion contains fats, minerals, and proteins that, if left intact, will produce off-flavors and undesirable aromas in the resulting sake. The more the outer portion is milled away, the higher the grade of sake. In theory, the more highly polished the rice, the cleaner and more ethereal the sake.

Fortification of sake produces positive attributes and is merely stylistically different. This is an important point because junmai is not necessarily better, but just different. The addition of alcohol to the mash (moromi) not only extends the shelf life of a sake, but also enhances the aromas within the sake by increasing their volatility. The brewer's alcohol in the mash functions as a soluble and helps to extract more flavor and aromas from the solids prior to pressing. It also can inhibit the activity of lactic acid bacteria, thus avoiding secondary fermentations or other negative side-effects.

The rules governing the daiginjō or junmai daiginjō categories stipulate that a rice polishing ratio of 50% or less (meaning 50% or more must be milled away) be adhered to. This results in the most labor-intensive of all sake categories. One can expect fruity aromas from these levels of sake. Both ginjō and junmai ginjō sakes require a rice-polishing ratio of 60% or less (meaning that 40% or more must be milled away). Although there is often an overlapping of flavor and aroma profiles between the daiginjō and ginjō levels, usually one can expect more aroma the higher one goes up (more highly milled rice) the quality category ladder. (Please look at the Sake Classification Chart.)

Honjōzō, the largest premium sake category, requires a rice polishing ratio of 70% or less (meaning 30% or more must be removed). This sake is not necessarily aromatic, but tends to have a clean, linear, and more ethereal profile than that of other categories. Junmai sake no longer has a minimum polishing requirement. As long as the polishing ratio is listed on the bottle and the sake is unfortified, it meets the criteria for the junmai category.

But the rice-milling and alcohol are not the only determining factors in the final taste of a sake. There are two measurements that often appear on sake bottles and may shed some additional light on what one might expect in the bottle of a particular sake as well. Neither one should be examined without the other: The SMV (sake meter value or nihonshudo) and acidity (sando).

1. The SMV (sake meter value or nihonshudo) - is actually a test for specific gravity. Although there is not a direct correlation to sweetness and dryness, it can be an indicator. A point to remember is that the higher the numeric value, the dryer (e.g. +5). The lower the numeric value, the sweeter (e.g. -35).
2. The level of acidity - A higher acidity often lends dryness and a perceived lightness to the sake. Just as with great Rieslings, although they can be high in sugar, the higher acidity found in them can often offset the sweetness of the wine, or in other words, bring balance to it.

There can be a discrepancy between what one perceives as sweet or dry and the clinical numeric values. They may or may not be in agreement with each other. It is important to note that these are just numbers, and one should not become too obsessed with them.

It is far more important to look, swirl, sniff, taste, and enjoy sake!