The increasing awareness of the danger of foodborne pathogens has promoted the search for new cost-effective methods of post-packaging pasteurization (PPP), especially in the meat and poultry industry. Thus, several developments in packaging have been initiated in response to these technologies.

PPP is designed to control Listeria contamination, in particular, after meat is processed and packaged, providing one more barrier for increased food safety. Contamination occurs after pasteurizing if small amounts of Listeria make it into the packaging. There may be a low detection at the time of packaging, but this pathogen will grow under refrigeration. Consequently, six to eight weeks later, this package can have hundreds of thousands of Listeria pathogens. With the goal to eliminate dangerous pathogens, an increasing number of meat processors have incorporated the latest heat and high-pressure methods to increase the level of food safety in their plants.

This quest has been spurred by the U.S. Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS), which has developed regulations and designations for food plants producing ready-to-eat meat and poultry to help ensure the safety of American consumers.

At this time, a number of companies have made it their mission to develop more effective and less costly PPP systems that can be more easily incorporated into meat-processing plants.

PPP 101

PPP is achieved primarily using irradiation, liquid — such as with hot water systems — or through a high-pressure processing method.

The science behind high-pressure pasteurization follows that microorganisms cannot survive in the deepest part of the ocean, where water pressure measures approximately 60,000 pounds per square inch. With this pasteurization method, vacuum-packaged meats are placed in high-pressure vessels filled with water. The water is then pumped out until pressure builds to between 40,000 and 90,000 pounds per square inch. This pressurization is known to destroy foodborne pathogens.

Food irradiation as it were, also known as cold pasteurization, is a food-safety technology designed to greatly reduce disease-causing germs from food. According to the USDA’s Food Safety Research Information Office (FSRIO), it is the process of exposing food to high levels of radiant energy, which penetrates into food, killing microorganisms without significant increases in the temperature of the food. The treatment of food with ionizing radiation kills bacteria and parasites that cause foodborne diseases. The process of irradiation only compliments proper food handling and storage. It does not replace it. Although controversial, studies performed by the World Health Organization, Food and Agricultural Organization, and International Atomic Energy Agency, have determined there is no harm in the food itself or risk to the consumers. The food itself does not become radioactive. There may be some nutritional content changes, but no more so than with other processing methods such as cooking, canning or pasteurization. Irradiation cannot be used with all food.

When using irradiation, there are three ways to generate energy — gamma rays, electron beams and X-rays. Each type varies in terms of the energy it takes and product penetration. While electron beams only penetrate 2 1/2 inches of the product’s surface, gamma rays and X-rays pass through several feet at a time. All three processes work by passing energy through food to break up the DNA of pathogens or spoilage organisms.

If you use irradiation ...

The international symbol for irradiation is called a radura. On a food label, this symbol is accompanied by the words “Treated by Irradiation” or “Treated with Radiation.” As of 1999, the FDA requires the Radura Symbol to be displayed on all irradiated foods sold for retail.

High hydrostatic pressure

Foodborne illnesses associated with E. coli-contaminated ground beef have forced numerous product recalls — and even shut down a business or two — during the past few decades. Ground-beef processors continue to look for ways to mitigate this food-safety risk.

One newer technology — high hydrostatic pressure (HHP) — looks promising in the ground-beef industry’s war against E. coli. According to “High Hydrostatic Pressure and its Possible Applications for Ground Beef”— an article written by Jim Marsden, senior science advisor for the North American Meat Processors Association and Regent’s Distinguished Professor of Meat Science at Kansas State University — the post-process pasteurization technology reduces vegetative bacteria through the use of high pressure, approximately 80,000 psi. Similar to the HPP technology used to control Listeriamonocytogenes in ready-to-eat cooked products, this process has little effect on flavor, vitamins or color.

Although a number of issues — including cost, regulatory status, optimum pressure/time and the feasibility of implementation in large grinding facilities — still need to be addressed, the article says the technology shows promise for eliminating virtually all E. coli O157:H7 in uncooked ground beef.

Source: Modern Packaging magazine, Summer 2008.

Levels of regulation

The USDA has developed three food-plant classification levels for ready-to-eat (RTE) processors, depending on the level of Listeria risk:

Alternative 3: Plants that rely on sanitation only, which are required to test and hold product prior to shipping.

Alternative 2: Plants that use either a post-lethality step or an inhibitor.

Alternative 1: Plants using both a post-lethality step and an inhibitor.

The USDA’s initiative encourages the meat industry to have a post-process lethality treatment as a means of eliminating Listeria on the surface of processed meats. This can be achieved before final processing, after processing, but before packaging or, in the case of PPP, post packaging.