When discussing the manufacture of today’s meat and poultry products, it is important to emphasize the connection between food safety and shelf life. There are two primary forces moving the use of antimicrobials and other intervention strategies in meats — the need to decrease and/or eliminate pathogens on meat and poultry, and the demand for “natural” products by consumers.

That said, advances in ESL (extended shelf life) technology for fresh meat and poultry not only allow meatpackers to increasingly push back “sell-by” dates, but also help processors ensure their products are safe for consumption.

Preserving meat is a concept that has been around for centuries. Today, “ESL” is a term that refers to products that have been manufactured using a certain process or packaged in a specific way that allows them to be bought and stored for a longer period of time than traditional perishable items.

Almost all meat products today incorporate some form of shelf-life extender. Some of these may have originally been intended for pathogen control. However, most ingredients in this segment are not bacteria specific, so there is a corresponding increase in shelf life. Most shelf-life extenders serve to interrupt or delay the natural growth process of bacteria. By slowing the bacterial growth, for example, you increase the time it takes to reach spoilage. The three types of shelf-life extenders are chemical preservatives, natural preservatives and processes. Most shelf-life extenders are labeled by their common names, such as vinegar or sodium lactate. Certain solutions used by meat processors to extend shelf life actually do double duty as antimicrobial agents, killing such virulent foodborne pathogens as E. coli O157:H7.

When bacteria spoil food, manifestations of spoilage such as a putrid or sour smell or slime formation appear when microbial numbers have developed into a very large population.

“Pathogens may require ingestion of large numbers of live cells or the cells may grow, produce toxins and die off, and although numbers of live cells may be low, ingestion of the toxin causes the illness,” says Romeo Toledo, professor emeritus of food science and technology for the University of Georgia. “Obvious manifestations of spoilage alert the consumer of the large microbial population that could likely harbor large numbers of pathogenic organisms as well. Thus, interventions that delay microbial spoilage will also avoid the development of large numbers of pathogens that may cause illness.

“We target the inhibition of growth of pathogenic bacteria as a ‘food-safety intervention’ strategy. We target inhibition of spoilage bacteria as a ‘food preservation’ or ‘shelf-life extension’ strategy.”

Although the stated objective of the intervention strategy may be different, says Toledo, the effect on the microflora is the same.

“The microflora in meats consists of a mixture of bacteria of different genera and specie,” he says. “Some genus may consist of pathogenic and non-pathogenic species, and within species there could be pathogenic and non-pathogenic strains. Thus, pathogens and non-pathogens coexist in meat and pathogenic and non-pathogenic organisms with the same requirements for growth may be present at the same time.”

Toledo says all antimicrobial treatments will affect both pathogenic and non-pathogenic microorganisms, therefore microbiologists who do not have the facility to safely handle pathogens generally utilize a surrogate non-pathogenic strain to test if the treatment can be effective in food-safety intervention.

Foodborne illnesses caused by pathogens that can grow at refrigeration temperatures such as Listeria monocytogenes, E. coli O157:H7, and Closridium botulinum type E has shaken the myth among food handlers that foods stored under refrigeration temperatures are safe, says Toledo.

“Pathogens are resistant to physical food-spoilage intervention treatments such as vacuum packaging, modified-atmosphere packaging, cooking and high-pressure processing,” he says. “Use of these treatments will also extend shelf life, since initial microbial numbers are low or the initial numbers capable of growing under the conditions within the package are low. However, the conditions also select for growth of pathogenic microorganisms if they happen to be in the product by surviving the physical treatment or through recontamination if there are no other organisms present to exert competitive inhibition.”

Thus, says Toledo, processors rely on multiple food-safety intervention strategies. A favored approach is the addition of antimicrobial agents into the meat with the marinade and as a surface spray before packaging. These approaches ensure that the antimicrobial agent is in the product and will be protecting the product when recontaminated after treatment with pathogens. The types of antimicrobial agents suitable for use on meats are specified in USDA’s “Safe and Suitable Additives for Meat and Meat Products.”

“The controversy is in the use of ‘chemical preservatives’ that are considered processing aids and are not required to be disclosed in the label, additives that are considered natural and allowed in products bearing natural claims, and natural antimicrobials specifically codified as excluded from the category of chemical preservatives,” he says. “USDA’s position that is being challenged is that inhibitors of pathogenic bacteria allowed in products bearing ‘natural’ claims can only be used when these inhibitors do not have an effect on shelf-life.”

Processors are allowed three categories of Listeria intervention strategies, says Toledo. “One of these involves a process or an additive that can eliminate Listeria,” he says. “The easiest and most-effective approach is to add an inhibitor that will prevent the growth of Listeria from reaching numbers that cause illness.”

Any treatment that reduces microbial numbers will reduce pathogens and reduce spoilage bacteria, says Toledo.

“Thus, the standard operating procedures of using antimicrobial agents in whole-carcass washes, in sprays applied to equipment and plant floors and walls during the sanitation regimen, and in allowed antimicrobials added directly to meat, will affect both product shelf life and safety,” he says. “Processors can use both sanitizing agents allowed for direct contact with foods or safe and suitable additives for direct addition to meat to ensure they are safe and have long shelf life.”

And the supplier marketplace is full of ingredients for such purposes. One can use acidulants like lactic, citric, erythorbic and ascorbic acids and lactic acid bacteria like probiotics or prebiotics in the animal, like in poultry to reduce Salmonella and maybe prolong the shelf life. There are also bacteriocins, some mold inhibitors and others. Antioxidants can also function as shelf-life extenders. Additionally, other natural ingredients have shown ESL promise as well. Ingredient suppliers and scientists have worked long hours testing the effects of natural ingredients on safety and shelf life, including seasonings like garlic and cinnamon, herbs like oregano and sage, and even dried-plum extract.

First Spice Mixing Co. Inc has responded to the need for Listeria and pathogen inhibition by creating Meatol.

“Meatol is a USDA-approved Listeria inhibitor,” says Marcy Epstein, director of research and development for the New York-based company. “It also cuts down the ability of other bacteria and pathogens to grow by 1 log.”

Epstein says Meatol has the added benefit of maintaining a product’s freshness, and can be equally effective in all types of emulsified meats, sausages and other salad products.

The development of the series of ingredients — Meatol and Meatol-P (for poultry) — is based on a proprietary blend of organic acids that, when used as directed, has minimal flavor carryover in the final product, says Epstein. Like other ingredients for ESL purposes, Meatol can be tumbled or mixed into a grind.

In addition to its Meatol line, First Spice offers a natural antioxidant made from spice extractives called Savorlok.

“Savorlok is used to reduce fat rancidity and lengthen shelf life in meats that are frozen or used in long-term storage,” says Epstein.

Shelf-life extension implies the reduction or elimination of spoilage over time, says Rick Hull, vice president of technical services and business development for Jefferson, Ga.-based World Technology Ingredients (WTI).

“When you say ‘shelf-life extenders,’ I commonly think of both natural and synthetic [chemical] ingredients which have a preservative effect by inhibiting the growth of microorganisms, both pathogenic and non-pathogenic in/on food,” he says. “In these terms, since the dawn of civilization, food safety and food preservation have been synonymous. To make a food safer, it was preserved by the use of naturally derived ingredients alone or in combination with simple processes. Ingredients such as salt, acidic fruit juices, sugars, spices, seasonings, organic acids, alcohol, and vinegars have been used for their multifunctional properties to both flavor and preserve food.”

Over time, says Hull, technology has evolved, and chemists have been able to identify the underlying modes of action of many of the naturally occurring ingredients that preserve food and make it safer.

“As a result, there are now many different synthetic chemicals available which are based upon systems originally identified in nature,” he says. “However, not all synthetic chemicals used to preserve food are based upon those found in nature. There are new chemicals emerging and approved for use in meats and poultry which do not exist in nature. Examples of synthetic chemicals which do not exist in nature are acidified sodium chlorite and lauric arginate.”

Regardless of whether a shelf-life extender is a synthetically or naturally based ingredient, says Hull, its mode of action is broad, and functions to make food safer by inhibiting the growth of all microorganisms associated with a food, thus preserving it while making it safer.

“Any ingredient or process which effects the total microbial population or their proportions in/on a food to make it safer will have a preservative effect — even when the use of such treatments is deemed instantaneous,” he says. “The only exception to food safety without food preservation is through the use of species-specific technologies such as bacteriocins and bacteriaphages which have limited use due to consumer perception, potential allergen issues and cost.”

The greatest challenge for ingredient suppliers such as WTI, says Hull, is how to source and develop new technology with the ever changing, inconsistent regulatory policies of the FSIS (Food Safety and Inspection Service) given consumers’ demand for natural, minimally processed products.

“WTI is focused on providing the food industry innovative ingredients which enable our customers to produce affordable, safe, better tasting foods,” he says. “We believe the horizon is limitless.”