How to cook sushi rice safely.

This article has been written by Pilla Founder, Liam Jones, click to email Liam directly, he reads every email.

It is recognised that mixing sushi rice with vinegar and salt seasoning will reduce the acidity of the mix, which in turn will help prevent the growth of bacteria and the formation of their toxins e.g. Bacillus Cereus.

This will enable it to be left out of temperature control for long periods, such as when making the sushi or sashimi. However, if we rely on this method we must be able to ensure the following;

• •The acidity i.e. the pH of the rice and vinegar mix must be checked. This acidity will have to be low enough to inhibit bacterial growth, i.e. below pH4.5. pH meters can be purchased from specialist stores or on-line.
• •The pH must be checked routinely and recorded or you must be able to show that it has been checked in some other way e.g. by using a bought in solution that has been tested by a manufacturer and following manufacturer’s instructions.

*If we are not able to standardise your vinegar/salt solution for the Sushi rice and are not able to check the pH level to ensure that it is below pH4.5, we must not allow the rice to be out of temperature control for long periods of time. If this is the case we will only prepare small amounts in advance, chill them down, store in the refrigerator and allow them to warm up to room temperature naturally just before service.

**Using the correct solution of vinegar to reduce the pH of Sushi rice to pH4.5 or lower, should help to inhibit the growth of pathogenic bacteria such as Bacillus Cereus, which is commonly found in rice. However, we must still ensure that we protect the rice against physical and chemical contamination. Additionally, it is the Sushi rice that is mixed with the vinegar solution. Any other food e.g. fish, meat or egg, added to the product, will not be protected and must not be left out at room temperature.

Preparation

Sushi rice should be cooled to 5°C or below within 2 hours of cooking or acidified. Cooled rice is recommended for making sushi intended for longer term storage and consumption (e.g. 2 days). Whereas hot/warm rice mixed with cold fish should be served immediately to the customer.

Follow a standardised recipe to ensure the correct volume of vinegar solution is added to a specific amount of rice. Consistency of ingredients is important to achieve a uniform pH throughout the sushi rice.

Acidify rice immediately after cooking with the vinegar, salt and sugar solution. Rice must be mixed thoroughly to reach a consistent pH and prevent pooling. Acidified rice can be kept at room temperature for up to 4 hours (recommended). Take a small amount of rice from the batch of acidified rice and insert a clean and calibrated pH meter into the sample. Wait until the reading remains stable for at least 5 seconds. Rice must achieve a pH of 4.6 or below.

This acidity is enough to inhibit multiplication of pathogenic bacteria. Check consistency of acidification by taking several pH measurements from different areas of the batch. Do not ‘mix’ the samples before taking the pH reading.

Avoid taking a measurement from a pool of vinegar solution as this will provide a false reading. Always follow manufacturer’s instructions for use and calibration of the pH meter. Never use pH strips to check acidification of rice.

Acidified rice can be kept at room temperature safely for a maximum of 4 hours. Warm rice (below 63°C) that does not achieve a pH of 4.6 or below must be discarded within 2 hours or cooled rapidly from 55°C to 20°C within 2 hours and refrigerated.