Sushi: A Practical Application of Microbial Control

Sushi is the most famous Japanese dish outside of Japan, and it is one of the favorites even among Japanese themselves. The term “sushi” initially referred to pickled fish conserved in vinegar, but in the present times it is generally understood to refer to bite-sized slices of raw fish served with rice. Sounds good so far – except, isn’t eating raw fish a bit dangerous?

Raw Fish
Raw fish can indeed contain microorganisms which can cause some harm. Anasakids, a kind of parasitic roundworms, are commonly found in fish and can cause gastrointestinal symptoms. To prevent infections, the Food and Drug Administration requires that fish to be served raw must be frozen at –20°C (–4°F) for seven days, or at –37°C (–35°F) for 15 hours. However, this procedure cannot totally eliminate or kill all pathogenic (that is, disease-producing) bacteria and viruses. Thus, there is always some risk of food poisoning caused by such bacteria as Staphylococcus aureus, Eschericia coli, and species of Salmonella and Vibrio associated with consuming any kind of raw seafood, including raw oysters, seviche, or carpaccio. It is for this reason that pregnant women and people with compromised immune systems should avoid all raw seafood.

But the raw fish is not the only issue here, as the rice component can also harbor some pathogens. Cooked rice left sitting at room temperature is vulnerable to growth of harmful microorganisms. This can be a problem for sushi preparations, but this is countered by preparing sushi rice with vinegar. The vinegar acidifies the rice, and at pH values below 4.6, the rice becomes too acidic to support the growth of pathogens. Additionally, restaurant temperatures can be kept cool in order to further discourage the growth of harmful microbes.

It is also believed that wasabi, the fiery horseradish-like green paste usually served with sushi, contains some antimicrobial properties which can also contribute to maintaining microbial growth at the minimum. However, the mechanism of action is yet to be discovered.

Because of these precautionary measures, most consumers can safely eat sushi meal after meal. Sushi is low in calories, and it is also a source of heart-healthy omega 3 fatty acids. When properly and carefully prepared, sushi is not only a very delicious dish but it is also one healthy treat.

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