While the Grade 1 and Grade 2 method for rating fish roe is common in the business-to-business sector of the caviar industry, labeling true sturgeon caviar as Select, Classic, Royal, Supreme or Imperial is a caviar grading system more widely used by caviar companies selling directly to retail customers. These grades are sometimes set by the producers of the sturgeon roe themselves, but usually what qualifies for Select, Classic, Royal, Supreme and Imperial product is decided by the company selling directly to end consumers, based on that company's standards for the size and color of the caviar beads/grains.
The lowest of the grades is "Select", which most of the time means below average, borderline Grade 2 product. While a few companies will use Classic grade for their slightly below average product instead, caviar that receives the Select grade, with darker color, and softer, smaller eggs, is a step down from Classic product.
“Classic” grade product almost always meets the average egg color and bead size for caviar from that species. Most of the time darker colored Grade 1 caviar is rated as Classic while the rarer product receives the above average grades of Royal, Supreme and Imperial.
“Royal” is the next step up and will typically be lighter in color or have larger grains than “Classic” caviar. Since larger egg sizes signify that the product was from an older sturgeon and the lighter egg colors are less common than the darker ones, the price can increase significantly when moving from Classic to Royal.
"Supreme" grade is seen less frequently than the other caviar grades, but when used it is usually given to product considered rarer than the "Royal" grade. Supreme caviar will be a very high quality product that has good sized grains, usually with lighter color than Classic or Royal. These rare pearls are beautiful to look at, but lack the golden glow of Imperial caviar.
The rarest and most expensive grade for a type of caviar is “Imperial”, which is reserved for product with the largest eggs and lightest color. Imperial caviar, also known as Golden Caviar, is a top-dollar product not just because it comes from older sturgeon, but because only an estimated 5% of all adult sturgeon will be able to produce bright golden colored eggs at any time in their life.
Keep in mind that these five grades are used mainly to account for sturgeon caviar's rareness (color and egg size), unlike the Grade 1 & 2 method which takes note of all the factors that can decide any caviar's quality. The Select, Classic, Royal, Supreme and Imperial grading method is not an exact science and what qualifies as a certain grade of caviar for one company might not be the same for a different company. Some companies will use these grades only to differentiate the lighter colored eggs from the darker, while others will use Royal or Supreme for caviar with larger grain size and Imperial for lighter egg color.
It is very important to know how the company selling caviar uses grades to rate their product, so that you can be sure the caviar you buy is not only rare but also of the desired quality. For example, there can be instances where a product is rated as Classic for its darker or smaller eggs, yet after testing is found to have a better flavor and texture than the rarer grades from the same species. The better you know how the company selling you the sturgeon caviar uses these grades, the easier it is to receive the quality, color and eggs size you desire.