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A natural line of defence

Use of natural antimicrobials is on the rise for food safety, stability and preservation purposes


The food industry has long known that in all areas of food consumption, Canadians favour more natural products – but that they also want those products to be safe. Combining these two demands, a new crop of naturally derived substances and methods is springing up across the food industry. Ancient antimicrobials such as vinegar are receiving serious makeovers, but new and natural cutting-edge approaches are also furiously being examined for their possible food safety, stability and preservation potential.

“Manufacturers are seeking label-friendly alternatives that are backed by science,” says Courtney Schwartz, Marketing Communications specialist at the Iowa-based ingredient-maker Kemin Industries. “Microbial safety is of concern to many food market segments, but particularly deli meat manufacturers are looking for solutions to improve their food safety program against Listeria monocytogenes (Lm) contamination.” Kemin offers BactoCEASE NV, a buffered vinegar product with an optimized flavour profile that ensures enhanced product food safety with minimal sensory impact, specifically in processed and ready-to-eat meats. It’s currently in the consumer-testing phase.

Phage technology
Another natural approach to meat preservation is a revolutionary packaging technology involving harmless viruses that can kill dangerous bacteria. Such viruses – known as bacteriophages or phages – have been used with some success in Russia and Eastern Europe for more than six decades. Scientists with the Sentinel Bioactive Paper Network based in Hamilton, Ont. have developed a system where phages are sprayed on packaging paper and attack pathogens such Listeria that can lurk on the surface of meat.

After they attach and enter a bacterial cell, phages take over the genetic machinery to produce new copies of themselves. Once a critical mass of phages is reached, they synthesize enzymes that dissolve the bacteria’s cell wall. The technology works on refrigerated meat, as well as on meat in modified-atmosphere and vacuum-packs. “We have demonstrated that phages attached to cellulose paper are still active after nine months,” explains Dr. Mansel Griffiths, director of the Canadian Research Institute for Food Safety at Ontario’s University of Guelph, and a Sentinel researcher.

However, the technology is not yet ready for commercial use. In studies published by Griffiths and his colleagues so far, it took 12 days at 4˚C to eliminate 100 E. coli O157:H7 cells/gram in raw, whole beef pieces. Griffiths acknowledges that under these storage conditions, the beef would have been spoiled in four to six days. In their trials involving control of Lm on oven-roasted turkey breast, the Sentinel scientists found that after about three to six days in most treatments, Lm recovered from phage attack and their numbers began to climb slowly. In other words, the phages initially reduced Lm growth but did not prevent it over 15 days at 4˚C – and many lunchmeats have a 30 to 60 day shelf life at 4˚C. There are also questions about the product’s limitation to just attack pathogens on the surface, and that pathogens could also eventually develop resistance to phages. Griffiths says the latter can be overcome by using a battery of different phages.

Natural sources
Naturally occurring “good” bacteria can also be added to food to prevent the growth of dangerous bacteria. One such commercial product is Micocin, produced by Toronto, Ont.-based Micocin Worldwide. It was approved by Health Canada last year (and is also approved in the U.S. and Mexico) to provide targeted protection against Lm in vacuum-packed wieners and some sliced meats. With wieners and sausages, a small amount of liquid solution is injected into the package, and in sliced products, the solution is sprayed over each slice face during slicing.

There are many other natural food protection avenues being investigated. Antimicrobial elements such as silver and copper have the ability to enter bacteria and interfere with their metabolism. And Japanese researchers at the University of Tokyo recently published a study on western parsley that suggests its antioxidant activity could be harnessed for food stabilization.

Professor Rick Holley of the University of Winnipeg adds mustard to the chopped beef/pork/fat/starter culture mix in a rotating bowl chopper as part of his research on antimicrobial compounds in hot mustard and deodorized mustard.

Along with Agriculture and Agri-Food Canada scientist Rong Tsao, Rick Holley, professor of microbial ecology of food and food safety at Winnipeg’s University of Manitoba, is examining antimicrobial compounds in hot mustard (isothiocyanates or ITCs) and deodorized mustard (glucosinolates, GSLs) in packaging for produce and meat, respectively. This industry-supported research is co-ordinated by Saskatoon, Sask.-based Mustard 21 Canada Inc., a non-profit corporation set up by the Saskatchewan Mustard Development Commission and the Canadian Mustard Association, and tasked with developing a strategic plan for the sector. Natural and synthetic films containing ITCs release them into the package atmosphere, which kills pathogenic bacteria. In contrast, GSLs in films are not released or antimicrobial until they are hydrolyzed by pathogens such as toxigenic E. coli, Lm and Salmonella.

Continuing developments
While all of these natural food preservation developments are certainly exciting, food manufacturers are also well aware of their current limitations. “Most processors realize they need to make some concessions in shelf life when moving to a natural preservative, and this limits the use,” notes Gil Bakal, managing director at New Jersey-based A&B Ingredients. A&B offers CytoGuard Stat-N natural shelf-life extenders, which are labelled as a natural flavour, and which are used in a wide range of refrigerated foods including soups, sauces and meat products.

Bakal says his company will continue to extend the functionality of products such as these, and hopes to offer some new versions in the coming years that will perform as well as synthetic alternatives. “The main obstacles to overcome when moving to a natural preservative are cost and efficacy,” he notes. “Essential oils are used in some products, but they have a strong flavour, so they are typically limited to products where the flavour is tolerable.” According to Bakal, the current primary methods of natural preservation remain large amounts of salt or vinegar and other acids. But, he says, “the trend towards natural preservatives will continue as more and more options become available.”