Colorado State University Extension
SafeFood Rapid Response Network


SAFEFOOD NEWS - Summer 2002- Vol 6, No. 4

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Update on Development of Safe Jerky Preparation Methods

In 1999, we reported on investigation of four alternative methods of jerky preparation that minimized survival of Escherichia coli O157:H7. Of the methods investigated, one method, the Hot Pickle Cure Preparation method, achieved a greater than 5-log reduction in inoculated bacterial populations during 10 hours drying at 145ºF and two others achieved near 5-log reductions. In 2001-02, Calicioglu, Sofos and Kendall evaluated the efficacy of the traditional marinade method vs. three other modified methods of marinating jerky for differences in survival of E. coli O157:H7, Listeria monocytogenes and Salmonella during drying for 10 hours at 140ºF.

The traditional marinade was taken from So Easy to Preserve, 4th edition, University of Georgia and had a pH of 4.3. The modified marinades included:

1. Prepare modified marinade with double the amount of Worcestershire sauce and soy sauce (Kikkoman milder soy sauce with 5% ethanol as preservative used), plus addition of 1.2% sodium lactate and 9% acetic acid to bring the pH of the marinade to 3.0;
2. Immerse slices for 10 minutes in vinegar (5% acetic acid) (pH 2.5), drain 2 minutes, then marinate overnight in refrigerator with traditional marinade;
3. Immerse slices for 15 minutes in 1% Tween 20 (a surfactant), drain 2 minutes, immerse 10 minutes in vinegar (5% acetic acid), drain 2 minutes, then marinate overnight in refrigerator with traditional marinade.

Beef slices (1/4 x 1 ½ x 3 ½ inches) were inoculated with one of three bacteria (E. coli O157:H7, Listeria monocytogenes or Salmonella), then marinaded using one of the above treatments. Products were then placed on dehydrator trays and the trays inserted into pre-heated (140ºF) American Harvest Gardenmaster dehydrators and dried for 10 hours at 140ºF. After drying, the jerky strips were held in the dehydrators overnight, then placed in sterile plastic bags for storage at room temperature. Two samples per treatment were analyzed after inoculation, after marination and 24 hour refrigeration, at 4, 7, and 10 hours drying, and on day 15, 30 and 60 of storage for bacterial populations, pH and water activity. The study was replicated twice with each of three bacteria, Salmonella, E. coli O157:H7 and Listeria monocytogenes.

For each of the bacteria studied, all three modified marinade treatments enhanced inactivation of bacteria over the traditional marinade treatment. After 10 hour drying, reductions in bacterial populations on jerky prepared using the traditional marinade were 2.6-5.0 log CFU/g, depending on the bacteria evaluated and media used to enumerate the bacteria. In comparison, reductions ranged from 3.5 to 6.6 log CFU/g when the modified marinade was used, 4.1 to >6.7 log CFU/g for the products prepared using the vinegar dip followed by traditional marinade and 4.8 to >6.7 when the 3-step process involving the use of Tween 20, followed by the vinegar dip and traditional marinade was used. While the 3-step process was somewhat better in inactivating bacteria than the 2-step vinegar-marinade process, it was generally not significantly better and Tween 20 is not available on the retail market.

Given the effectiveness of the vinegar dip step in enhancing inactivation of pathogenic bacteria that may be present on beef slices prepared for drying, and the acceptability of this treatment in consumer taste panels, we are recommending this as an alternative method for preparing jerky in the home. The two methods in the enclosed handout both produce an acceptable product and offer the consumer a choice between a saltier product (Hot Pickle Cure method) and a tarter product (Vinegar-Marinade method).

Molds on Foods, What to Do?

We've all had it happen to us: we finally decide to use that long-forgotten cheese only to open the wrapping and find what used to be a nice orange cheddar now has white patches on its surface. Really convinced that cheddar was a necessary ingredient for that perfect sandwich idea, we wonder if we can still safely use the cheese and salvage our lunch plans.

There's good news and bad news. Sometimes, as with hard cheeses, you can cut off the mold along with an inch around and below the spot, and then use the rest of the product. However, with soft foods like jellies and sour cream, it's best to discard the moldy product as mold filaments may extend below the surface.

Molds are tiny fungi that live on plant or animal matter. They have three main 'body' parts: root threads that extend into the material the mold uses for food, a stalk that rises above the food, and spores located at the end of the stalks. It is the spores that give molds their various colors and cause the mold to spread. These spores are found almost everywhere in our environment, and are transported by air, water and insects.

There are several health dangers associated with molds. Some molds cause allergic reactions and respiratory problems. Other molds can produce mycotoxins or aflatoxins. Mycotoxins are poisonous substances that can make a person ill. They are produced mainly by molds found in grain and nuts, but have also been found on many types of produce. Aflatoxins are poisons produced by certain molds that are found in foods and animal feed, particularly in field corn and peanuts. Since this type of toxin can cause cancer, many countries, including the United States, monitor its presence on implicated food items. In addition, certain poisonous mushrooms (which are also fungi) produce a toxin that cannot be removed by cooking, canning, or any other method of food processing. The only way to avoid food poisoning is to eat only mushrooms known to be safe for human consumption.

Certain kinds of molds are not only safe, they are the defining characteristic of some popular foods. For example, blue cheeses such as Roquefort, Gorgonzola, and Stilton are made using the Penicillium family of molds. Brie and Camembert, some salamis, and dry-cured country hams all have surface molds that are a normal part of the food. While the mold on these types of cheeses and salami is safe to eat, the mold on dry-cured country hams should be scrubbed off before cooking.

To prevent the unwanted appearance of colorful fuzzy spots, keep a clean kitchen and follow good food safety practices:

• Several times a year, clean the refrigerator with a tablespoon of baking soda dissolved in a quart of water; rinse with water and then dry it.
• Wash dishcloths and hand towels and change sponges often; if a musty smell develops, the items are harboring mold.
• If possible, maintain a humidity level in your house of less than 40%. · At the grocery store, avoid foods that appear to have mold growth.
• Use leftovers quickly before mold has a chance to grow.
• Keep cold foods refrigerated - don't allow them to sit out on the counter for more than 2 hours.
• After opening a can of food, transfer the remaining portion into storage containers and refrigerate. So what do you do when mold is already present?
• Avoid smelling the moldy food - it can cause respiratory problems.
• If the item is covered with mold, discard it. Wrap it in a small paper bag or plastic and put it in a covered trash can that animals and children cannot get into.
• Clean the area of the refrigerator or cupboard where the food was stored to prevent further spread of spores.
• Examine other foods that might have touched the moldy item. Mold spreads rapidly in fresh produce.
• Refer to the enclosure, "Moldy Food: When to Use, When to Discard," and for a copy of the original article, see www.fsis.usda.gov/oa/pubs/molds.htm

Adapted from:
USDA Meat and Poultry Hotline. Molds On Food: Are They Dangerous? Food Safety Focus. April 2002.

Updated Monday, August 29, 2011