Sushi

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Sushi is normally regarded as a potentially hazardous food yet is often displayed and sold out of temperature control.

These studies investigated the safety of the products and their handling.

Sushi consists of cold, cooked rice acidified with vinegar that is shaped into bite-sized pieces and topped with raw or cooked fish. They are also sometimes formed into a roll with fish, egg, or vegetables and wrapped in seaweed (nori). Other names and similar products include nigiri, nigirizushi, nori rolls, Californian rolls, maki, makizushi, inari and inarizushi.

2006-2007 study

An Australian national survey from June 2006 to June 2007 determined the food handling practices and microbiological quality of retail sushi products.

Samples in the survey were tested for:

  • chemical aspects—pH & water activity—of acidified rice
  • microbiological quality indicators and pathogens present in sushi
  • histamine levels in raw seafood.

89 outlets displaying sushi in enclosed cabinets or moving conveyor belts, sometimes called sushi trains were randomly included in ACT, NSW, NT and SA.

Winter and summer samples were identified and compared.

The survey also included a questionnaire on how:

  • rice was acidified and stored
  • sushi was prepared and displayed.

The survey was conducted under the Coordinated Survey Plan of the Food Regulation Standing Committee's (FRSC's) Implementation Sub-Committee (ISC). NSW Food Authority was the lead agency for the survey.

2006-2007 results

Microbiology

Generally very good with acceptable results for:

  • 98.6% of sushi rice samples
  • 94.6% of sushi samples.

Sushi

6 samples were categorised as potentially hazardous due to elevated levels of Bacillus cereus.

Sushi samples had higher levels of faecal coliforms and E. coli in the summer months.

Histamine

All samples of raw seafood were found to be within the Food Standards Code limit for histamine levels.

Full report

For all unacceptable results, follow-up action was undertaken commensurate with the level of risk posed.

Safety control measures for sushi rice are discussed and references are included in the report.

Table of contents 
Executive summary
1. Introduction
2. Survey Objective
3. ISC Coordinated Food Survey
4. Food handling questionnaire
5. Sample collection
6. Method of analysis Assessing microbiological quality of sushi
7. Results
- Survey responses
- Acidification and storage of sushi rice
- Preparation and display of sushi
- Microbiological and chemical results
- Acidified sushi rice
- Sushi – winter samples
- Sushi – summer samples
- Combined results
- Histamine testing
8. Discussion
- Control measures for sushi rice
- Preparation and display of sushi
- Microbiological quality of sushi
- Faecal coliforms and E. coli
- Bacillus cereus
- Coagulase positive staphylococci (S. aureus) - Salmonella
- Listeria monocytogenes
- Vibrio parahaemolyticus
- Histamine
9. Follow up action
10. Conclusion
11. References
12. Attachments
- Food Handling questionnaire for sushi businesses
- Summary of questionnaire responses

2009 follow up

Early in 2009 the Food Authority undertook a small survey as a follow-up to the earlier national study.

The updated snapshot used 36% of the same outlets. Sushi products were purchased from 15 outlets across Sydney.

Samples were tested for up to 7 different microorganisms.

2009 results

Results from this snapshot were consistent with those from the 2006-2007 study.

For any unacceptable results, follow up action was undertaken consistent with the level of risk posed.

Microbiology

Generally very good with acceptable results for:

  • all rice samples
  • 94.8% of sushi samples.

No sample was classified as hazardous, or likely to present a food safety concern.

Histamine

All samples of raw seafood were found to be within the Food Standards Code limit for histamine levels.

Full report

Table of contents 
1. Introduction
2. Method
3. Results & Discussion
4. Conclusion
5. References

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