Colorado State University Extension
SafeFood Rapid Response Network


SAFEFOOD NEWS - Summer 1998 - Vol 2 / No. 4

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Improving the Safety of Extended Shelf Life Refrigerated Foods

In response to consumer demand, more and more refrigerated foods with an extended shelf life are appearing on supermarket shelves. Some examples are ready-to-eat luncheon meats and complete heat-and-eat meals. These foods have received minimal processing or precooking and have a long shelf life. Obviously, these foods present a challenge to ensure microbiological quality and safety. To ensure safety, these foods must be stored at 50 F. (10 C.) or less since refrigeration is the key preservation measure.

Two types of microorganisms that could grow during extended refrigerated storage or temperature abuse are of concern. Psychrotrophic and mesophilic pathogens are capable of growing under these conditions. Psychrotrophic pathogens, which include some bacteria, yeasts, and molds, grow slowly at refrigerator temperatures and grow faster at higher temperatures. Mesophilic pathogens can survive under refrigeration and resume growth once the temperature increases.

Since some pathogens can cause illness when only a few cells are ingested, food processors need to be diligent in fully evaluating and preventing the hazards that may exist in refrigerated foods with extended shelf lives. Some of the control methods that may be used in preventing and minimizing microbial contamination of product and inhibiting the growth of or destroying microbial contaminants include:

• Good Manufacturing Practices (GMPs), high levels of Sanitation and Hygiene. Processors need to select high-quality raw materials with low levels of microorganisms.
• Use of Multiple Barriers / Hurdles or the "hurdle concept". This approach combines several factors at subinhibitory concentrations that can effectively control microorganisms in refrigerated foods. The synergistic interaction between these factors means that lower levels of each factor can be used.
• Ingredients added that are barriers to microbial growth.
• Heat treatment, for example, pasteurization.
• Modified Atmosphere Packaging (MAP). MAP extends product shelf life by reducing oxygen and/or increasing gases, such as carbon dioxide, in the food product environment.
• Storage temperature and shelf life.
• Potential non-thermal methods, such as food irradiation.

Michael Doyle, from the Center for Food Safety & Quality Enhancement, has recommended that processors solicit the input of qualified food microbiologists to fully evaluate the safety of treatments used to extend product shelf life before implementing such controls. The point he makes is that processors must be vigilant in applying such antimicrobials by assuring that a potential microbial safety problem is not introduced as a result of controlling spoilage microorganisms. For example, the use of modified atmosphere packaging may keep a product from molding, but it may create an anaerobic environment that is favorable to the growth of Clostridium botulinum.

Sources:

• IFT Status Summary, Extended Shelf Life Refrigerated Foods: Microbiological Quality and Safety, Vol. 52, No. 2, Feb. 1998.
• Food Safety Notebook, Vol. 9, No. 3, March 1998.

Updated Monday, August 29, 2011