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Appendix 2: The 5-log 10 Reduction using thermal technology

1.0 Meaning of 5-log10 Reduction Performance Standard

Foods may be contaminated with microorganisms such as disease-causing bacteria and protozoan parasites, as well as bacteria, yeasts and molds that do not cause disease, but which can spoil product. When conditions in foods are suitable, microorganisms use the opportunity to multiply to very large numbers.

  • To simplify counting of such large numbers of microorganisms, scientists use the term: "log10".
  • "1-log10" represents a value of 10 microorganisms per g (gram) or ml (millilitre) of food;
  • 2-log10 = 100 organisms per g (or 10 x10 = 102)
  • 3-log10 = 1,000 organisms per g (or 10 x 10 x 10 = 103)
  • 4-log10 = 10,000 organisms per g (or 10x10 x10x10 = 104)
  • Similarly, 5-log10 = 100,000 organisms per g of food (or 10 x10x10x10x10 = 105)

Pasteurization processes to address food safety issues are expected to destroy or inactivate numbers of pathogens in the food. This is measured in terms of "log10 reductions". Using the same principle as above, each 1-log10 reduction should reduce the number of organisms (or pathogens) identified as a concern, by a factor of 10.

So, a process achieving a 1-log10 reduction would be expected to reduce the level of pathogens in the food by 10 times, e.g., from 100 initially down to 10 microorganisms per g in the final food product. A 2-log10 reduction reduces levels by 10 x 10 = 100 times, e.g., from 1,000 initially, down to 10 microorganisms per g of final food product, etc.. This is illustrated in the table below:

If starting number of microorganisms per ml of juice before processing is Log reduction achieved during processing Reduction in the level of microorganisms in the juice Final number of microorganisms per ml of juice after processing will be
100,000 (or 105) 1-log 10 times 10,000 (or 104)
100,000 (or 105) 2-log 10x10 = 100 times 1,000 (or 103)
100,000 (or 105) 3-log 10x10x10 = 1,000 times 100 (or 102)
100,000 (or 105) 4-log 10x10x10x10 = 10,000 times 10 (or 101)
100,000 (or 105) 5-log 10x10x10x10x10 = 100,000 times 1 (or 100)

The level of pathogens present in unpasteurized juice/cider will probably be far less than 105 per ml and would probably be in the range of 10 to 102 per ml of liquid. The 5-log10 reduction performance standard applied to the most resistant pathogens of concern in the final juice/cider product would therefore be expected to result in a final number of microorganisms that is less than 1. The consumption of a product containing this level of pathogens is considered to represent an acceptable level of risk.

2.0 Microbial Hazard Identification Applied to Unpasteurized Apple Juice/Cider

Health Canada considers that the primary microbial pathogens of concern in unpasteurized apple juice/cider are the bacterial pathogen E. coli O157:H7 and the parasite Cryptosporidium parvum, because they have been linked to a number of illness outbreaks associated with this particular commodity. Although there have been recent outbreaks of Salmonella spp. due to unpasteurized citrus juices, there have been no recent Salmonella spp. outbreaks in unpasteurized apple juice/cider. No outbreaks have been associated with Listeria monocytogenes in apple juice/cider or other high acid fruit juices, and research shows that L. monocytogenes will survive poorly in apple cider stored at 4°C or 10°C. Therefore, L. monocytogenes is not considered to be a primary pathogen in apple juice/cider. Also, Salmonella spp. and L. monocytogenes are less heat-resistant than acid-adapted E. coli O157:H7.

Other fruit juices/ciders, and non-thermal processing technologies, may have a primary pathogen of concern that differs from apple juice/cider treated thermally. These juices/ciders and non-thermal processing technologies will be looked at on a case-by-case basis. However, due to their association with juice/cider, we recommend that the lethality of any treatment, including non-thermal treatments, should take into consideration the control of the primary pathogens: E. coli O157:H7 and C. parvum.

2.1 Pasteurization Requirement

Health Canada supports the use of a minimum 5-log10 reduction requirement in the most resistant pathogen(s) of concern, as an indicator for general fruit juice/cider pasteurization. This total reduction is to apply directly to the final juice/cider product. If two primary pathogens have been identified, then the 5-log10 reduction would apply to the most resistant.

3.0 Continuous Processes In Use Commercially for Apple Juice/Cider

The following time and temperature combinations for continuous processes are in use on commercially produced apple juice/cider. To know whether each combination meets or exceeds a 5-log10 reduction in the pathogens of concern, we performed calculations based on data generated in the references that are cited below. The data are considered to apply to apple juice/cider of pH values of 4.0 or less, which are comparable to pH values of juices used in the referenced studies. Juice/cider with a pH value greater than 4.0 may require other validation studies.

pH: A measure of the acidity and alkalinity of a product on a scale from 0 to 14, where 7 is neutral. Lower pH values (<7) indicate more acidic products.

Process 1: 168°F (75.6 °C) for 2.5 seconds achieves

  1. an 11-log10 reduction of E. coli O157:H7
    (reference: Mazzotta, 2001; D168 °F = 0.0037 min, z =10.5 F° or 5.8 C° in single-strength apple juice of pH 3.9)

  2. an 11-log10 reduction of Cryptosporidium parvum
    (reference: Deng & Cliver, 2001; D168 °F = 0.00375 min, z =10.5 F° or 5.8C° in apple juice of pH 3.7)

Conclusion: Calculations indicate that the minimum 5-log10 reduction for the above pathogens would be achieved at 168°F (75.6 °C) for 1.1 seconds, in juice/cider of pH value of 4.0 or less.

Process 2: 160 °F (71.1°C) for 6.0 seconds achieves

  1. a 4.7-log10 reduction of E. coli O157:H7
    (reference: Mazzotta, 2001; D160 °F = 0.0215 min, z =10.5F° or 5.8C° for single-strength apple juice of pH 3.9)

  2. a 4.7-log10 reduction of Cryptosporidium parvum
    (reference: Deng & Cliver, 2001; D160 °F = 0.0215 min, z =10.5 F° or 5.8C° for apple juice of pH 3.7)

Conclusion: Calculations indicate that the minimum 5-log10 reduction for the above pathogens would be met with 160°F (71.1 °C) for 6.5 seconds, in juice/cider of pH value of 4.0 or less.

The data above implies that C. parvum (parasite) in apple juice appears to have a similar heat resistance to the bacterial pathogen E. coli O157:H7 in apple juice. Therefore, until more data is generated or becomes available to show otherwise, Health Canada considers both E. coli O157:H7 and C. parvum as the most resistant pathogens of concern in apple juice/cider.

3.1 Comparison to Recommendations from the United States

Health Canada's conclusions on the above process times and temperatures were independently derived and are based on scientific references that were referred to by the United States Food and Drug Administration (USFDA) March 3rd 2004 Juice HACCP Hazards and Controls Guidance. In that document, the U.S. also recommends that for apple juice, a thermal process should achieve a 5-log10 reduction in the pertinent pathogens that are determined to be of concern. Within the limitations of the data in the references cited, the processing guidance provided by Health Canada in Section 3.0 is considered to be similar to the U.S. recommendation (i.e., 160°F for 6.5 seconds for Canada versus 160°F for 6 seconds for the U.S.).

3.2 Other Options Available to the Industry

Non-thermal processes and non-apple fruit juices/ciders will be considered on a case-by-case basis. Juices/ciders treated with non-thermal processes may be considered novel foods, as defined under B.28 of the Food and Drug Regulations. Manufacturers or importers of novel foods are required to submit a premarket notification to the Novel Foods Section, Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch, Health Canada and receive a written response from the Branch that the information in the notification is sufficient to establish that the food is safe for consumption. This written notice must be received before a novel food can be sold or advertised for sale. A specific ultra-violet process for the treatment of unpasteurized, unfermented apple juice and cider products has been previously approved for use in Canada. For more information on novel foods submissions, please contact:

Novel Foods Section
Bureau of Microbial Hazards, Food Directorate
Health Products and Food Branch
Health Canada
Tunney's Pasture
Ottawa, Ontario K1A 0L2
Fax: (613) 952-6400
E-mail: food-aliment@hc-sc.gc.ca
Website: www.novelfoods.gc.ca

References

Deng, M.Q. and D.O. Cliver. 2001. Inactivation of Cryptosporidium parvum oocysts in cider by flash pasteurization. J. Food Prot. 64 (4) pp. 523-527.

Mazzotta, A.S. 2001. Thermal inactivation of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella and Listeria monocytogenes in fruit juices. J. Food Prot. 64 (3) pp. 315-320.

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