Jenny Scott is Senior Director in the Office of Food Safety Programs at the National Food Processors Association in Washington, DC, where she has held a variety of positions since 1980. NFPA is a not-for-profit trade association that represents the food processing industry on scientific and public policy issues involving food safety, nutrition, technical and regulatory matters and consumer affairs. Scott is responsible for providing expertise and guidance on issues and policies related to microbial food safety and HACCP as well as technical assistance and crisis management related to NFPA member problems. She received an A.B. degree in biology from Wellesley College, an M.S. in bacteriology from the University of Wisconsin, and an M.S. in food science from the University of Maryland. She has published numerous research papers and book chapters in the areas of microbial food safety and food processing. She has been active in professional associations such as the American Society for Microbiology, the Institute of Food Technologists and the International Association for Food Protection, where she was president in 2000-2001.
Food Safety Magazine: What are the drivers that make time/temperature considerations throughout the food supply chain such a critical factor in today’s food safety and quality assurance/quality control (QA/QC) programs?
Jenny Scott: In general, the drivers for the food industry with regard to time/temperature measurement and monitoring include regulatory compliance, Hazard Analysis & Critical Control Points (HACCP) or prerequisite program implementation, and quality assurance to maintain the cold chain or to ensure proper heating of foods. Ultimately, quality considerations drive the need for time/temperature measuring and monitoring activities more so than safety issues.
Of these, regulatory compliance generally is not the most significant driver, because temperature regulations are limited. Most of the regulatory compliance comes into play in segments of the food industry where HACCP is mandatory, such as seafood, meat and poultry. This would apply to cases in which the processor has put a temperature-related critical control point (CCP) into the HACCP plan. Temperatures in HACCP plans generally tend to relate to instances in which you are cooking product or cooling product, or in the case of seafood and the scombroid species, where the hold time also is critical. Also, the Pasteurized Milk Ordinance (PMO) has some temperature requirements in it, and since the PMO has been adopted by all the states there are some temperature requirements for Grade A dairy products. In the meat industry, there have been some policies, rather than straightforward regulations, related to time/temperature. For example, there is a U.S. Department of Agriculture (USDA) policy that poultry should be shipped at 40F, which has become a de facto regulation, because everyone in that industry adheres to it.
Time/temperature is a factor that for certain companies, certain products and certain operations will be considered critical and will they deal with it as a CCP in a HACCP plan. However, many companies consider time/temperature measurement and control as part of a prerequisite program that contributes to overall safety but where the primary reason for these controls is quality. For example, achieving the shelf life that is required to market refrigerated products means that time/temperature must be controlled from the get-go. If not, we won’t get the desired shelf life and thus we won’t maintain the quality. Indeed, the product will go bad long before it becomes a safety issue. There are some exceptions to that; for example, with seafood, we know that there are certain species of fish in which microorganisms can grow and generate histamine if the temperature isn’t properly controlled. In these types of products, there will be a lot more emphasis on time and temperature control in order to prevent a safety issue from arising.
There certainly have been issues of time/temperature control with respect to Listeria monocytogenes. But when a company is dealing with the type of product for which the regulations don’t allow any Listeria monocytogenes, the company typically already has put the controls in place to ensure to the extent possible that the organism is not present. In this case, time/temperature to control growth becomes fairly secondary, as an added safety measure. Clearly, if you have a product for which you cannot prevent Listeria monocytogenes contamination, then keeping the temperature down for the period of time until it gets to the consumer is important to keep the numbers of Listeria down, which is the key to preventing illness.
In fact, time/temperature controls really focus on controlling the growth of microorganisms, including pathogens that grow in or on the product. Thus, it really comes back to the hazard analysis that a manufacturer will conduct for a specific product to decide whether there are specific pathogens of concern that need to be controlled through time and temperature and how to go about implementing control when and where it is appropriate.
Although I’m speaking primarily about time/temperature on the cooling side, the same issues apply on the heating side. In most operations, a heating step is a CCP, because that is the kill-step for pathogens such as Salmonella, E. coli O157:H7 and the vegetative cells of sporeforming pathogens. On the cold side of the chain, Listeria monocytogenes is frequently a target pathogen. When cooling down a meat item, Clostridium perfringens usually is the primary organism of concern. With seafood products, processors must consider Clostridium botulinum, particularly since strains of this pathogen can grow at refrigeration temperatures. Again, it comes right back to the hazard analysis, where it is very important for companies to identify the pathogens of concern for the various segments of their operations and consider the effect of any time/temperature processes with respect to food safety.
The food processing industry spends a lot of effort in measuring and monitoring cold chain temperatures, be it during storage of raw materials, storage of finished product prior to shipping or storage in the distribution facilities. When a manufacturer has time and temperature under control, quality and safety issues don’t figure in until after the product has left the manufacturer’s control. The issue of time/temperature control during transportation has been discussed often during the past few years. Some of the thinking has been centered on considering this a critical factor, and in the mid-1990s, FDA and USDA issued an advanced notice of proposed rulemaking related to time/temperature control during transportation.
However, although people often talk about cold chain time/temperature in terms of safety concerns, if you look at where the problems have arisen, very rarely has there been an instance that’s safety related with respect to temperature control during transportation. In those rare instances, problems have arisen due to gross temperature abuse of product. And while you’d be hard-pressed to think of a safety problem in the last 20 years that is related to temperature control during transportation, except perhaps for scombrotoxin in seafoods, the food industry would tell you that there have been a number of quality issues. Companies do turn back product simply because of temperature abuse during transportation, which is a problem, just not necessarily a safety one.