Food Surveillance Australia New Zealand
Special Edition - Survey Special
Spring 2001
How safe are soft, chilled noodles?
What can be done to improve standards?
How to keep soft, chilled noodles safe?
How safe are soft, chilled noodles?
Soft, chilled noodle products are gaining in popularity in this age of convenience foods. Designed to be poured out of the packet and into the wok, soup or salad, the noodles are a great time saver for many families.
The noodles are generally partially cooked by boiling during processing and usually only require re-heating before consumption. They have a short shelf life and if not stored under refrigeration will deteriorate quickly.
During ANZFA' s Review of Microbiological Standards, it was evident that there was insufficient data on the microbiological status of soft, chilled noodles to determine their risk status. In addition, since 1997 there have been four recalls of noodle products in Australia, two of which were due to high bacterial levels (see figure 1). There were no recalls of noodle products in New Zealand during this time.
Figure 1 - Recalls of noodles in Australia Product Year Reason for recall Refrigerated stir fry noodles 1997 Coagulase positive staphylococci >15,000/g Coliforms >1100/g Standard plate count 5.4x108/g Stir fry rice noodles 1999 Possibly contained iron particles Corn and chicken flavoured noodles 2000 Fine wire fragment contamination Noodle meal kit 2000 Higher than expected bacterial numbers in the noodle component
The Survey
Twenty-five noodle brands from Australian and New Zealand companies were sampled four times over the course of the survey to assess their microbiological safety and quality. Samples were all tested during their last week of shelf life between July and September 2000.
In addition to testing for microorganisms and microbial toxins, some Australian samples were also tested for sodium borate. Sodium borate (also known as borax) and boric acid are not permitted by the Food Standards Code as food additives. However, they are sometimes illegally added to foods to improve colour, texture and flavour.
Samples of noodles were collected by officers from ANZFA, and health departments from all States and Territories. Samples in New Zealand were collected by officers from the Ministry of Health. A short questionnaire, requesting product information such as cooking instructions and other labelling information, was completed at the time of sampling. Temperatures of the products at the point of sale were also recorded.
Each sample consisted of five packets of noodles and these were transported on ice to the Australian Government Analytical Laboratories in Sydney and Melbourne for microbiological and chemical analyses. New Zealand samples were forwarded to ESR in Christchurch for microbiological analysis.
The survey found that nearly all the noodles sampled would have been safe to eat with the exception of one sample that contained food poisoning bacteria. However, approximately three quarters of the samples showed signs of poor food processing and handling and five brands contained high levels of borax.
Analysis of samples was undertaken in Sydney and Melbourne by the Australian Government Analytical Laboratories (AGAL) and in New Zealand by the Institute of Environmental Science and Research Ltd (ESR).
Our survey found that soft chilled noodles are convenient and easy-to-use but need to be handled with care.
Results & discussion
Test results were compared against a range of criteria (see Assessment Criteria) to determine their food safety, food processing/handling and borax status.
Each sample consisted of five packets of noodles and if one or more packets met the unsatisfactory assessment criteria then the sample (all five packets) was considered unsatisfactory.
Food safety tests
All samples complied with the survey food safety criteria for coagulase positive Staphylococci,Escherichia coli,Listeria monocytogenes, Salmonella species and Staphylococcal enterotoxin, (figure 2).
Figure 2: Results of food safety tests
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One sample did not comply with the criteria forBacillus cereusas it contained 22,000 cfu/g.
Bacillus cereusproduces spores, that are stimulated to germinate during cooking, and also toxins that are responsible for two forms of food poisoning: the first results in acute vomiting with some diarrhoea that starts 1-3 hours after eating contaminated food, the second results in diarrhoea that starts 9-18 hours after eating contaminated food. Bacillus cereusgrows best in the temperature range of 30°C - 40°C.
Food processing/handling tests
The tests for Standard Plate Count (SPC) and Enterobacteriaceae are useful to establish the adequacy of food handling as a trend over time. For example, if results of monthly sampling are rising it may indicate that food handling standards are falling.
The SPC includes all bacteria present in a food, both good and bad. Some foods which are made from bacteria e.g. yoghurt, will naturally have a high SPC.
The test for Enterobacteriaceae measures those bacteria that are normally found in the gut of animals and humans and also in soil and on plants. Not all types cause food poisoning.
Over three quarters (76) of the 97 samples had a SPC in excess of one million cfu/g and two thirds of samples (68) had Enterobacteriaceae levels over 100 cfu/g, (figure 3).
Figure 3: Results of food processing / handling tests
This indicates that food handling may have been inadequate at some stage in the food processing, transport and display chain with the noodles having been
- inadequately cooked and/or
- contaminated and/or
- stored under inadequate temperature control.
Temperatures of noodles at point of sale
Food poisoning bacteria are able to multiply more quickly at temperatures above 5°C. So the longer the food is above 5°C the more time bacteria will have to multiply. If a small number of food poisoning bacteria contaminated the food at the factory, they could multiply to numbers sufficient to cause food poisoning if the food is transported, stored or displayed above 5°C.
Of the 93 samples for which temperatures were recorded over three quarters (73) were displayed at temperatures below 5°C. However, 18 samples (19%) were stored between 5°C and 8°C and two above 9°C, (figure 4).
Figure 4: Temperatures of noodles at point of sale
Foods that have been stored above 5°C for longer periods of time generally have higher SPC and Enterobacteriaceae numbers. In this survey about three quarters of the samples had high SPC or Enterobacteriaceae levels, indicating temperature abuse at some stage.
Borax (Sodium borate) testing
Borax is sometimes added to food to improve its colour, texture and flavour. However, because borax can be very toxic, the Food Standards Code does not permit borax to be used in foods.
Borax (Na2B4O7.10H2) and boric acid (H3BO3) are used as detergents, water softeners and weak antiseptics. The acute LD50 in rats (the dose causing death in approximately 50% of test animals) is in the region of 5,000 mg/kg. If children swallow 5-10g of borax it can cause shock and death. Ingesting smaller quantities can lead to symptoms such as nausea, vomiting, diarrhoea and abdominal pain (USDA,1995).
Five different brands (16%) of the 32 samples analysed for borax contained over 100mg/kg. One sample contained over 1200mg/kg, (figure 5).
The non-complying samples were referred to the relevant state government authority for further investigation and appropriate follow up action was taken.
Figure 5: Results of borax (sodium borate) testing
Assessment criteria
The samples were analysed for the following:
a) Food safety tests to assess if the noodles contained microbial toxins or pathogenic bacteria in numbers that could cause food poisoning in susceptible people.
b) Food processing/handling tests to assess if the noodles contained sufficient numbers of bacteria to indicate they may have been contaminated or kept out of temperature control at some stage in their manufacture, transport or storage.
c) Borax testing to assess if the noodles contained sufficient amounts to indicate borax may have been added during manufacture. The Food Standards Code does not permit borax to be added to foods.
If one of the five packets in a sample met the following criteria, the sample was considered unsatisfactory:
Food safety tests
- Bacillus cereusmore than 10,000 colony forming units per gram (cfu/g)
- Coagulase positive staphylococci more than 10,000 cfu/g
- Escherichia colidetected
- Listeria monocytogenesmore than 100 cfu/g
- Salmonella species detected
- Staphylococcal enterotoxin detected
Food processing/handling tests
- Enterobacteriaceae more than 100 cfu/g
- Standard plate count more than one million cfu/g
Temperature at point of sale
- Above 5°C
Borax (Sodium borate)
- More than 10 mg/kg
Summary of findings
The results of the survey have highlighted a number of potential problems with soft, chilled noodles.
The high number ofBacillus cereusbacteria in one product could be a problem if the product was not heated thoroughly before serving.
The high SPC and Enterobacteriaceae counts suggest the products could have been
- Inadequately cooked during processing
- Contaminated during processing
- Stored under inadequate temperature control during processing, transport and display.
While the temperatures at the point of sale were generally good it was not known what the temperatures had been before display.
The high sodium borate levels in a small number of products was an unexpected finding and shows that some companies are not complying with the Food Standards Code.
What can be done to improve standards?
Businesses manufacturing, transporting or displaying soft, chilled noodles could use food safety programs to check product formulations, identify steps in the process where noodles could become contaminated and/or where temperatures could be abused. Actions can then be taken to monitor conditions to ensure that food safety is maintained from factory to retailer (See How to keep noodles safe?).
Further information is being developed by ANZFA to assist manufacturers to improve process hygiene and possibly to label products to indicate noodles should receive some heat treatment before consumption.
Consumers also need to be advised to handle soft, chilled noodles with care, especially if using them in salads or stir fries. If they do not live near their shopping centre or will not be going straight home, consumers are advised to place chilled foods in an insulated container to keep them cold (See How to keep noodles safe?).
Consumers are advised to use an insulated container to transport chilled foods on long journeys.
How to keep soft, chilled noodles safe?
The survey has identified that soft, chilled noodles are potentially hazardous foods as they can support the growth of food poisoning bacteria. Therefore, ready-to-eat noodles must be cooked thoroughly during food processing. All soft, chilled noodles must be transported and stored at safe temperatures from the factory to the consumer. Use the checklists below to assess if you are handling noodles with care.
Processing stage
- Are noodle ingredients (e.g. flour) free from high microbial loads and free from pathogens?
- Are noodles protected from:
- physical contamination (e.g. wire fragments from machinery)
- microbiological contamination (e.g. from dirty hands and equipment)
- chemical contamination (e.g. from borax)?
- Are staff trained in basic food hygiene?
- Are cooking times and temperatures monitored and recorded?
- Are temperatures of coolrooms monitored and recorded?
- Is a cleaning schedule in place, so premises and equipment are kept clean?
Transport, Storage and Display stages
- Is the food transported below 5°C?
- If a refrigerated truck is used, is it pre-cooled before loading food?
- Are records kept of the temperatures in the truck?
- Is the food transferred from the vehicle directly to a cold storage/display area?
- When food is received at the store is the temperature checked and recorded to make sure that it is below 5°C?
- Is the temperature of the cold storage/display area monitored and recorded?
- Do staff know what to do with the food if monitoring shows that the temperature is rising?
Consumer stage
- Is food purchased last during a shopping trip?
- Is cold food purchased last in the supermarket?
- If you don' t live near your shopping centre or will not be going straight home, do you place chilled foods in an insulated container to keep them cold?
- Is cold food loaded directly from the car into the refrigerator?
- Does the refrigerator keep food cold?
- Is there a thermometer in the refrigerator and is it checked regularly?
- Are noodles used before their use by date?
- Are hands washed before handling noodles?
- Are stir fried noodles heated thoroughly (steaming hot)?
Articles from Food Surveillance Australia New Zealand may be reproduced with an appropriate acknowledgement.
Material and opinions contained within do not necessarily represent the position of ANZFA, NZ Ministry of Health, AQIS and State and Territory Health Departments.
Food Surveillance welcomes your enquiries and suggestions.
Please contact:
Mark Salter
Monitoring and Evaluation
Telephone: (02) 6271 2222
Fax: (02) 6271 2278
Email: info@anzfa.gov.au
ISSN 1445-8713
Published by:
Australia New Zealand Food Authority.
© Commonwealth of Australia 2001
October 2001