In 2003, food preservatives and shelf-life extenders were a $196.8 billion industry in the United States, and that number is projected to grow to $257.7 billion in 2008, according to "Adding Life to Foods: Trends, Techniques and Opportunities in Food Preservation and Shelf Life Extension" (2003, Business Communications Company, Inc., Norwalk, CT). A press release for the report includes the forecast that some consumers will continue to be dubious of synthetic preservatives, making way for natural preservative ingredients and the increase of packaging and processing alternatives that allow for the reduction or elimination of synthetic ingredients.
Setting hurdles
Products such as pickles or jerky are designed with lower pH and/or water activity to inhibit the growth of microorganisms. In many other cases, antimicrobial ingredients provide a cost-effective way to prevent organisms that cause illness or spoilage. Hurdle technology relies on multiple methods to inhibit microbial growth.
"The number of hurdles added to a food product, ingredients such as salt, sugar and use of antimicrobials and processing parameters such as pH, time and temperature, will all affect the shelf life and safety of a food product," says Cathy Dorko, product manager, Food Protection NA, Danisco USA, Inc., New Century, KS. "The more hurdles there are in place, the more challenging it will be for pathogens and spoilage microorganisms to grow in a food product, resulting in safer products with longer shelf life. In many cases, the protection or shelf-life extension helps to offset the higher cost of pathogen control."
Going natural
Consumer perception has driven much of the new development in extending shelf life. "The majority of the work is focused on natural solutions, due to industry and consumer demand for cleaner labels," says Dorko. For example, she cites the development of new generations of antimicrobial systems based on nisin and rosemary to inhibit Listeria and other pathogens in meat. "New herbal and/or spice extracts are being evaluated for oxidation inhibition," she notes.
Rosemary extract contains phenolic compounds, a natural solution to oxidation, a reaction that can lead to off-flavors associated with warmed-over meats and rancid fat. But it can work with nonmeat products. A study on kalsec.com tackles off-flavors in pretzels during staling. The researchers found that rosemary extract added to the pretzel dough inhibited staling, as measured by the presence of hexanal in the headspace. Rosemary extract itself has a flavor, and suppliers offer ingredients suited to applications that require blander products.
In addition to rosemary, oregano, sage and thyme contain antioxidant phenols (thymol, rosmarinic acid), as do cloves and allspice (eugenol). These phenolics are generally volatile and present in the spices' essential oils.
Nisin, an antimicrobial produced by fermentation, is effective against gram-positive bacteria. Application areas for nisin include dairy products and meats. Natamycin is also a fermentation product and protects against yeast and mold. A common application of natamycin is as a surface treatment on cheese and dried and semidried cured meats.
