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Introduction
The purpose of this document is to provide information on measures for controlling the risk of pathogen growth during the cooling of cooked meat products after a heat treatment.
Control Measures
After a heat treatment, products need to be cooled rapidly to prevent the outgrowth of heat-shocked pathogen spores including Clostridium species (i.e., no more than a 1-log colony forming units per gram (CFU/g) increase of C. perfringens and no growth of C. Botulinum) and other pathogens of concern such as Staphylococcus aureus.
To control the cooling phase and make sure it is fast enough, operators develop a valid cooling schedule for every type of heat processed product, and monitor the chilling process to ensure that each lot met the cooling schedule.
The following cooling schedules are known to minimize growth of pathogenic bacteria in/on the products.
Slow cooling
Parameters:
- The internal temperature does not remain between 49°C and 4°C for more than 20 hours; and
- The cooling process:
- causes a continuous drop in product's temperature; or
- controls the product's surface temperature so that it does not stay between 49°C and 20°C for more than two (2) hours.
These parameters for slow cooling are applicable for a meat product that is formulated with:
- a water activity (aw) of above 0.92, no less than 120 ppm of sodium nitrite (or its equivalent in KNO2) and a brine concentration of 3.5% or more in the finished product; or
- a water activity (aw) above 0.92, no less than 40 ppm of sodium nitrite (or its equivalent in KNO2) and a brine concentration of 6% or more in the finished product; or
- a water activity (aw) that is less than or equal to 0.92 at the beginning of the cooling process, with or without nitrite (such as dried products); or
- a water activity (aw) of above 0.92, no less than 180 ppm of sodium nitrite (or its equivalent in KNO2) and a brine concentration of 2.3% or more in the finished product.
Example:
Brine concentration in the finished product = [% salt / (% salt + % moisture in end product)] × 100
Example: If 2.8% of salt in the formulation and the end product has a moisture level of 72%, the brine concentration is:
{(2.8÷100) ÷ [(2.8÷100) + (72÷100)]} × 100 =
[0.028 ÷ (0.028 + 0.72)] × 100 =
2.8 ÷ 0.748 = 3.74%
The following US Food Safety Inspection Service cooling parameters (as per compliance guidelines in Appendix B, 1999) may also be used for the slow cooling of ready-to-eat meat and poultry products cured with a minimum of 100 ppm of ingoing sodium nitrite under certain conditions.
Parameters:
Products are cooled so that the maximum internal temperature is reduced from 130°F (54.4°C) to 80°F (26.6°C) in 5 hours and from 80°F (26.6°C) to 45°F (7.2°C) in 10 hours (15 hours total cooling time).
Conditions for the use of these parameters are as follows:
- Meat and poultry products do not contain levels of reducing agents (e.g., sodium erythorbate, sodium ascorbate) that reduce the efficacy of nitrites, unless there are sufficient levels of other Clostridium perfringens inhibitors (e.g., sodium lactate or salt), that can be demonstrated to compensate for the presence of reducing agents. For example, if sodium erythorbate is used at a concentration of 557 ppm, the ingoing sodium nitrite level of ≥120 ppm will result in sufficient inhibition of C. perfringens.
- Meat products are not held in a significantly anaerobic state during cooling (as might occur if they are vacuum packaged for prolonged periods of time between formulation and cooking), unless there are sufficient levels of other C. perfringens inhibitors (e.g., sodium lactate, salt or elevated nitrites), that can be demonstrated to compensate for the anaerobic conditions. For example, sodium nitrite used at 180-200 ppm will result in sufficient inhibition of C. perfringens in product vacuum packaged for 24h between formulation and cooking.
Notes:
- These conditions were established based on the following publication: Redondo-Solano M. et al. Effect of meat ingredients (sodium nitrite and erythorbate) and processing (vacuum storage and packaging atmosphere) on germination and outgrowth of Clostridium perfringens spores in ham during abusive cooling. Food Microbiology 35: 108-115 (2013).
- This option applies only to cooked products
Rapid cooling
During cooling, the product's maximum internal temperature must not remain between 54°C and 27°C for more than two (2) hours nor from 54°C to 4°C for more than 7 hours.
Alternatively, products consisting of a piece of intact (excluding tenderized) muscle such as roast beef, moist cooked beef, turkey breast or pork loin, may be cooled to 4°C within 7.5 hours from the initiation of the cooling process while taking no more than two hours for the 50°C to 20°C temperature zone.
The following US Food Safety Inspection Service cooling parameters (as per compliance guidelines in Appendix B, 1999) may also be used for the rapid cooling of ready-to-eat meat and poultry products provided that:
- During cooling, the product's maximum internal temperature does not remain between 130°F (54.4°C) and 80°F (26.6°C) for more than 1.5 hours nor between 80°F (26.6°C) and 40°F (4.4°C) for more than 5 hours. This cooling rate can be applied universally to cooked products (e.g., heat treated or fully cooked, intact or non-intact, meat or poultry) and is preferable to option (2) below.
- The chilling of cooked products begins within 90 minutes after the cooking cycle is completed. All products should be chilled from 120°F (48.8°C) to 55°F (12.7°C) in no more than 6 hours. Chilling should then continue until the product reaches 40°F (4.4°C). The product should not be shipped until it reaches 40°F (4.4°C).
For both options, the cooling between 120°F (48.8°C) and 80°F (26.6°C) does not take more than 1 hour, and chilling must continue between 55°F (12.7°C) and 40°F (4.4°C).
Interrupted cooling
Cooling may be interrupted for up to 4 hours for cooked products that are cooled from 54°C to 18°C within 2 hours, if the products are:
- kept below 18°C during the 4 hours, and
- protected from post cooking contamination (e.g., covered, wrapped, etc.), and
- cooled to 4°C within 2 hours immediately at the end of the 4 hour holding period.
Deviation from the cooling process
When the operator is conducting a risk assessment on a product because they intend to distribute a product that was subject to a cooling deviation, the following should be considered.
- Predictive modelling programs should be used to evaluate the safety of the product. The operator must enter data into the model reflective of the worst case scenario for the cooling deviation as well as the product characteristics (i.e., the lowest plausible concentrations of C. perfingens inhibitors in the product such as salt, pH, nitrites must be entered).
- If the model predicts no more than a 1-log CFU/g increase of C. perfringens and no growth of C. Botulinum, the product may be considered for release. However, end product sampling for Clostridium perfringens (viable cells) should also be conducted on any product subject to a cooling deviation to provide additional assurance of the safety of the product. Note: negative end product test results for C. perfringens should not be used as a basis to release product subject to a cooling deviation in the absence of modelling results or if modelling indicates predicted C. perfringens growth greater than 1-log CFU/g.