Does Nori Go Bad

In this brief article, we will answer the question, “does nori go bad?”. We’ll also tell you how nori is made, how long does it last, and some tips to extend its shelf life. 

Does Nori Go Bad?

Not exactly. Nori (dried seaweed) has a relatively long shelf-life, especially if it is stored under proper conditions. Nori stored in aluminum foil packaging keep its quality for about 90 days at 25 °C (1).

But like many other vegetables, the ‘best-by’ date on a package of nori is not its expiration date. It simply tells you that nori will not retain its original flavor and aroma after this period. 

So simply put, you can safely use and consume nori even after its ‘best-by’ date has passed unless there are visible signs and symptoms of spoilage. 

How Long Does Nori Last?

An unopened packet of nori can last for about two to three years if it remains sealed. However, the shelf life of nori depends mainly on its best-by date, how it has been prepared, and how the packet is stored. Plastic packaging such as high density polyethylene (HDPE) and polypropylene (PP) as well as aluminum foil has good water and gas molecular migration barrier properties, making them suitable for packaging nori which has dry characteristics and easily becomes moist so that its quality is maintained (2).

An opened packet of nori can last for about one to two years, and again, the conditions above apply. Remember that an opened package of nori speeds up the decline of taste and overall quality. The most important factor regarding nori acceptance is texture. When exposed to air, nori becomes moist, flexible, not crunchy and easy to tear (2). 

As mentioned, nori is dried and lacks moisture, so it has a long shelf life and can be consumed safely after its best-by date. However, to enjoy the best flavor of this form of seaweed, it is recommended that you consume it before its best-by or best-before date. Dry sheet products such as nori will easily become damp and increase in moisture content if left unpackaged so that their shelf life is relatively short (2).

How is Nori Made?

Nori is a dried edible seaweed commonly used in Japanese cuisine. It is made from different species of red algae Pyropia, such as P. yezoensis and P. tenera. Seaweed is one of the marine plants belonging to the benthic macroalgae that lives attached to the bottom of the waters. There are thousands of seaweed species, but only a few are cultivated for industrialization and human consumption. The drying process is generally done by using sunlight or an oven. (3).

Nori has a strong distinctive flavor and is mostly used to wrap sushi and onigiri rolls.

Nori is made by slicing edible seaweed and pressing it into thin sheets. It is quite similar to the process of making paper.

How Can You Tell If Nori Has Gone Bad?

The key features to look for when any food item is suspected of spoilage are color, smell, and taste. Here are a few signs to look out for which will indicate that nori has gone bad and is not fit for consumption. 

• Any changes in color from green to a more yellowish or brown tinge indicate that the nori has spoiled. 
• If the packet is exposed to moisture or placed on a wet surface for a long time, mold may start to grow on the seaweed’s surface. Moreover, exposing the nori to wetness will cause it to become sticky, soggy, leathery, and eventually rot. 
• Apart from moisture, another factor to look out for is heat. If the nori is subjected to high temperatures for extended periods, it will become brittle and eventually turn to dust.
• Nori has a distinctive salty smell and taste, owing to the additional flavors added to it. If your nori has lost its flavor or smells rancid and sour rather than salty like the ocean, its quality time may have passed. 

Seaweed is cultivated in sea water. There is a general assumption that human pathogens occur on seaweed in the same density and composition as in the surrounding water masses. Hence, the localization  of the seaweed is an important factor concerning microbiological food safety. However, seaweed food products may also get contaminated or re-contaminated during handling and processing. High initial bacterial loads normally affect the shelf life and sensorial quality of the seaweed negatively, but do not necessarily imply that the food is unsafe to consume (3). 

Can You Consume Expired Nori?

Yes, you can safely use and consume a packet of nori that has passed its expiry date; however, if there are any signs of spoilage like the ones listed above, immediately discard it. Bacteria, viruses, yeast, and molds may constitute potential microbiological health hazards in edible seaweed. Regarding bacteria, separation is made between (i) pathogenic bacteria that may be present in such small amounts that it does not lead to a directly observable effect (flavor, color, aroma) of the product, but as by ingestion of minute quantities may still cause food poisoning and even death, and (ii) spoilage bacteria, which is not necessarily harmful to the consumer, but which degrade the product. Studies have identified pathogenic Bacillus spp., Vibrio spp., and Aeromonas spp. as the main inherent bacteria that are of special concern for the food safety of seaweeds. Bacillus spp. forms heat-resistant spores and can produce heat-stable toxins, whereas Vibrio and Aeromonas spp. can grow under chilled temperatures (3).

Remember: always be aware of these signs when using any food product, especially if it is past its best-by date. Consuming spoiled food carries significant health risks such as food poisoning, so always practice food safety and enjoy your foods before their expiry date. And if you experience any problems, consult a health professional immediately.

How Can You Store Nori To Extend Its Shelf Life?

The recommended temperature for storing nori is between 35 and 38 degrees Fahrenheit; temperatures above 40 degrees Fahrenheit encourage bacterial growth on the nori. This is why it is preferred that an unopened and opened packet of nori be stored in the fridge.

To refrigerate an opened packet of nori, transfer the contents of the packet into an air-tight glass jar/container or a re-sealable zip-lock bag. Place a ‘do not eat’ package of silica gel inside the bag or container to absorb excess moisture and ensure that the seaweed stays dry. 

If you live in extremely humid and heated environments, you can freeze your nori to extend its shelf life. If you’re freezing nori sheets that have already been exposed to moisture, they will end up developing a chewy flavor. So always freeze closed and still dry products.

However, freezing nori is not recommended because it will add moisture to the seaweed once it is thawed. Also, the overall quality will decline as well.

Conclusion

In this brief article, we will answer the question, “does nori go bad?”. We also told you how nori is made, how long it lasts, and some tips to extend its shelf life. 

If you have any more questions or comments please let us know.

References

1. Liviawaty, Evi, Sapinatun Namira, and Eddy Afrianto. Shelf Life of Nori from Gracilaria Sp. With Alumunium Foil Packaging Based on The Accelerated Shelf Life Test Method. Int J Quant Res Model, 2021, 2, 1-10. 
2. Liviawaty, Evi, et al. Changes In Organoleptic Characteristics of Nori From Gracilaria Sp. During Storage With Different Types of Packaging. Int J Res Comm Serv, 2020, 1, 35-40.  
3. Løvdal, Trond, et al. Microbiological food safety of seaweeds. Foods, 2021, 10, 2719.