Keeping food safe: Sanitising fruit and vegetables

Chinese, Italian, street food or Australiana, regardless of the cuisine, serving delicious, comforting and exciting meals is something that all chefs strive for. Serving up memorable dining experiences as customers embark on new taste sensations or share old favourites with family and friends produces great pride and satisfaction in their work. One experience that they don’t want customers to take away with them is a case of food poisoning.

Food poisoning is alarmingly common in Australia with an estimated 5.4 million cases a year. Caused by food contaminated with bacteria, viruses or toxins, the symptoms can be very unpleasant, ranging from mild stomach upset to long term health problems and even death in rare cases.

With the multitude of food going in and out of commercial kitchens, proper preparation and handling is vital. This series of articles will address safe practises for food handling with a special emphasis on using cleaning products to keep your customers safe. Today’s article will focus on cleaning and sanitising fresh fruit and vegetables to remove bacteria and prevent cross contamination.

When most people think of food poisoning, things like meat, eggs and seafood come straight to mind. Little do they know that there can be some other big offenders that would seemingly slide under the radar. Fresh fruit and vegetables to be served raw in salads, coleslaws, desserts and garnishes can pose a problem as they can be exposed to harmful bacteria from soil. Below are some tips and processes to minimise the microorganisms present on fruit and vegetables to greatly reduce risk of exposure.

Tips for handling fruit and vegetable

  • Check the quality of fresh produce from the supplier to ensure that it is clean, undamaged and fresh. Damaged produce can allow pathogens to enter the tissues and chlorine may not reach the pathogens
  • Sanitise fruit and vegetables in a mild solution of chlorine (instructions below) to minimise bacteria
  • Keep raw, unsanitised produce away from ready to serve food to prevent cross contamination
  • Store sanitised produce in the fridge to prevent bacterial growth. Store ready-to-serve, sanitised produce above raw items in the fridge
  • Wash ready-to-eat fruit and vegetables on the day you intend to use them
  • Use cleaned and sanitised chopping boards and work surfaces to prevent cross contamination
  • Always wash your hands before handling and preparing food
  • (NSW Food Authority 2006)

How to sanitise fruit and vegetables

Washing raw produce with a chlorine solution has been shown to reduce the number of microorganisms present on raw fruit and vegetables.

This process is especially important for produce that will be prepared for raw consumption such as salads, coleslaw, fruit salad etc. To sanitise fruit and vegetables, clean them in water to remove all visible dirt and then sanitise them by soaking in 100 ppm (free) chlorine for 5 minutes.

Sodium hypochlorite (commonly known as bleach) is a chlorine based chemical that is a permitted washing agent for food manufacture. When making up the sanitiser solution it is essential that quantities be measured out accurately. In addition, appropriate chemical training for operators preparing the sanitising wash is also important and must also be demonstrated (NSW Food Authority 2006).

Before you start –

Undamaged clean, fresh produce: It is important to purchase clean, undamaged, fresh produce. Damaged produce can allow pathogens to enter the tissues and chlorine may not reach the pathogens. Chlorine rapidly loses its effectiveness on contact with dirt, organic matter and when exposed to air, light or metals. Therefore, make sure all soil is removed before soaking in the chlorine sanitising solution and periodically check the level of sanitiser if you are washing a lot of vegetables.

Wash water temperature: The temperature of the wash water and the chlorine sanitising solution is also important. The wash and sanitising water temperature should be slightly warmer (about 5 – 10 degrees) than the produce to prevent water being sucked inside the fruit or vegetable. If the wash water is cooler than the vegetables, water can be absorbed into the tissues along with any bacteria present.

Contact time: For the chlorine to work effectively, it needs to be in contact with the food surface for five minutes to be able to kill bacteria. This is known as contact time and it is very important to allow the produce to soak in the Bleach solution (NSW Food Authority 2006).

Application-

  1. Make sure your produce is free of dirt, undamaged and pre-cooled in a refrigerator.
  2. Pre-wash in water (at least 10°C warmer than the temperature of the produce) to remove excess soil and dirt.
  3. Making the chlorine solution.
    • Make sure you follow your occupational health and safety requirements for handling and preparing chlorine solutions,
    • Use ONLY food grade chlorine (sodium hypochlorite, NaOCl), it must be labelled as food grade.
    • Use a single, designated sink for washing fruits and vegetables, mark a fill line in the sink for the correct water level. Fill with water up to the correct level and then add the Bleach. You should make only enough for one batch and use immediately. Ideally you should purchase test strips to check the level of chlorine and record the date, time and chlorine concentration in a special book every time you make up a Bleach sanitiser solution. Monitor this level regularly if washing a large quantity of produce.
    • Measure out the Bleach, use the table below to achieve the volumes below for 100 ppm concentration of Bleach solution.
  4. Add washed produce and agitate to ensure that all surfaces are wet and there are no bubbles.
  5. Soak for 5 minutes or as directed by the manufacturer.
  6. Do not rinse (if the final level of chlorine residue in the final product complies with the FSC 1.3.3).
  7. Dilute and dispose of the Bleach solution in accordance with your sewerage authority requirements.
  8. Prepare and use the next batch of Bleach solution only when needed, do not store.
  9. If you are using a commercial product make sure you carefully follow the manufacturer’s instructions for quantities, contact time and water temperature.
  10. (NSW Food Authority 2006)

Dilution Rate Table –

Agar Bleach with 5% available (free) chlorine can be diluted using the table below to achieve a 100 ppm concentration of available chlorine.

Sanitiser Fruit and Vegetables

(NSW Food Authority 2006)

References:

NSW Food Authority 2006, Industry Guide to Developing a Food Safety Program (Hospitals and Aged Care). Available from: <http://www.foodauthority.nsw.gov.au/_documents/industry_pdf/cleaning_sanitising_fresh_produce.pdf> [10 June 2015]