Nori is made from a type of red algae called Porphyra, the most commonly consumed seaweed. Diners are most familiar with nori in the form of crisp, black sheets that wrap around sushi rice. Porphyra is commercially farmed in Japan and other countries. After harvesting, it is chopped into a pulp, spread onto drying sheets, strained, dried and finally very lightly toasted. Raw nori sheets are available for those who on a raw food diet. There are different grades of nori, and the Japanese have highly discriminating tastes when it comes to this seaweed product. Some nori brands, usually inexpensive foreign products, sell for as low as 5 cents per sheet while at the highest end, nori can cost as much as $50 per sheet. Some brands are available only in Japan due to high local demand and limited availability. The Japanese consider seaweed harvested from specific regions in Japan to be of supreme quality and will pay dearly for it. Although nori imported from China and Korea were thought to be of low quality (and therefore cheaper), production methods and regulations in those countries have resulted in improved quality.
How can you distinguish between a high quality nori sheet versus a lesser grade? The Porphyra seaweed flavor varies depending on where it is grown and when it is harvested. It helps to know the background of the brand you buy and where it harvests its seaweed. But this information is not always printed on the package label and even if it were, chances are your Japanese language reading skills are lacking. So here are other clues:
Color: Raw nori sheets have a brownish-red to purplish color, and they are hard to find. Most nori sold today is very lightly roasted to bring out its flavor and to enhance its texture. When nori is roasted, its color deepens to black. Choose nori with a dark black color. Over-toasting changes the color to light green. Moderate quality nori may have a hint of a deep green sheen. Lighter green nori is substandard. One side of the nori sheet should be shiny; the other a flat color.
Thickness: Nori should be the right thickness. Hold up a sheet of nori and look at it. Nori that is too thin and of poor quality may have holes or spaces. You should not be able to see through it. On the other end of the spectrum, nori that is too thick will be tough to bite and chew when moistened by sushi rice.
Texture: Nori is highly susceptible to deterioration from humidity. Soft nori sheets have been damaged by exposure to moisture. Choose nori that is crisp, almost brittle. Nori becomes soft quickly when rolled with wet sushi rice so it is best to make sushi rolls right before you serve it. That is why good sushi chefs always directly present hand rolls to the diner for immediate eating. This way, the nori will retain its delightful crispness. Even nori that is wrapped around sushi rice should never be chewy.
Aroma: Good quality nori should have a faint smell of the ocean.
Flavor: It is hard to describe the flavor of high quality nori but you know it when you taste it. I had eaten nori all my life but was downright shocked to taste Japan nori from a woman who brought suitcases full of top grade nori from a recent trip. She said that this type of nori could not be purchased in the US. My husband and I were awestruck by its delicious, deep umami flavor and crispness!
You should handle and store nori with great care. Store nori in an airtight container and freeze it. Once the package is opened, use the nori as soon as possible. This should be a pleasure as there are so many ways to enjoy it.