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Q&A: Keeping Food Safe on Memorial Day

It’s Memorial Day, and while many of us in the northern U.S. brave the elements to barbeque and picnic year-round, the last weekend in May signifies the “official” start of grilling season.  

With that in mind, Food Safety News recently sat down with our publisher, Bill Marler, to talk about summer food safety.

memorial-day-bbq.jpgQ:  What is some standard “picnic fare” that is considered dangerous?  What makes this food potentially dangerous?

A:  Foods that have the ability to support bacterial growth are frequently identified in foodborne illness outbreaks, many potentially hazardous foods are common at picnics. Foods with a water activity above .88, and with slight acidity (pH between 4.2 and 7.0), have the right chemistry for harmful bacteria to multiply and increase.

Dry foods generally considered safe include chips, crackers, bread of all kinds, cereal, cookies, chocolate candy, and fermented sausage.  Acidic foods generally considered safe include BBQ sauce, cheese, many salads with a lot of mayonnaise and mustard, fruit, soda, Kool-Aid, hard-boiled eggs in the shell, hard acid candy, fruit pies, condiments (olives, picles, mustard, mayonnaise), salami, yogurt, and fermented sauerkraut.

The rule of thumb is that foods that contain protein are the most dangerous, when these other factors are also present.

Foods that share these attributes include eggs and egg-based dishes, meat, fish, cooked vegetables, some other fruits and vegetables like cut melons or sliced tomatoes, and many dairy products. Complex food mixtures that contain cooked vegetables, like potato salad, and possibly coleslaw, must also be treated as temperature sensitive. To prevent bacterial growth in a susceptible food, the temperature of such foods during cold storage should never exceed 41 degrees, or drop below 135, if served hot.

Insulated coolers with dry ice are the preferred cold storage methods. Simple thermometers are available and should be placed in the cooler box. Another rule is that if the food has failed to meet safe temperatures for greater than 4 hours since it was prepared, the food should be discarded.

Since not all bacteria are destroyed during cooking, even cooked foods are dangerous when bacterial growth is permitted. Many ready to eat foods can also become toxic or infectious as well, when bacteria multiply.

The picture becomes more complex when you include foods that receive frequent handling. Such handling may sufficiently contaminate a food, and there may not need be temperature abuse to create an unsafe condition. Cross contamination between raw and cooked or ready to eat food is a key hazard to avoid and subsequent growth is then of course also possible in many foods, further increasing the risk.

Effective hand washing during prep is more effective when a convenient safe water supply exists, but pre-picnic planning can help. Bottled water can be used for hand washing even at remote sites, and hand soap and paper towels are easily carried along. There may be some utility of hand sanitizing lotions at a cook out, but the best use of hand sanitizers is as an adjunct to proper hand washing and good hygiene.

Q: What are the rules of thumb for the outdoor grilling of steaks, hamburgers, hot dogs, and chicken?

A:  In addition to the hazards that can result from growth of bacteria, some foods especially raw animal derived foods, are intrinsically contaminated and require thorough cooking at any time but especially when grilling out.  Most of the contamination found on the outside of raw beef, poultry and seafood is easily destroyed through thorough standard cooking methods cooking but there is a special problem with destroying internalized bacteria such as E. coli in ground beef, making safe cooking ultra important.

Safe cooking for any food requires that the internal temperature of the food be tested for doneness. Certain levels of time and temperature are needed for various foods dependent on the amount of contamination present and the properties of the food itself. Cooking poultry products to 165 degrees internally will destroy the infectious bacteria, Salmonella and Campylobacter, in 15 seconds or less on both the exterior and interior of the poultry. Less temperature is needed for E. coli in ground beef (155 for 15 seconds) and even less for steaks, seafood and pork- temperatures of 145 for 15 seconds being adequate for them. For food cooked in a pit underground, such as a luau pig, bacteria can be killed by heating slowly between 50 and 125 degrees F, and then cooking to greater than 145 degrees F for 3 minutes.  While there is growth during slow heating, the food is safe, because the food gets pasteurized during cooking, and toxins are not formed.

Hot dogs are considered cooked, ready to eat, non shelf stable foods by the USDA. Therefore there is no recommended safe internal temperature when cooking hot dogs, but they should be refrigerated prior. Listeria is a pathogen that often contaminates hot dogs and luncheon meats. If plant sanitation programs fail to prevent this bacteria from contaminating a hot dog, then a basic 145 temperature should be sufficient as long as excessive bacterial growth was prevented.

Problems arise with temperature measurements when cooking thin foods, e.g., when taking the internal temperature of a hot dog. Thin foods are hard to manipulate on a grill when trying to insert a standard thermometer, often leading to not testing and/or under-heating. Hot dogs placed beside hamburgers when cooking on a flat surface can be cross contaminated by raw meat juices, and they should be thoroughly heated.

Thin meats like steaks, chops and chicken breasts may be difficult to test for the same reason as hot dogs, and practice is needed. The temperature probe must be located in the geometric center or thickest part of the food, and some foods do not cook evenly especially on a flame grill or charcoal fire pit.

Doneness of any cooked food cannot be judged based on color and appearance. Only an accurate cooking thermometer is sufficient. While a thermometer is needed, cooking skill is also required. Thin probed thermometers and thermometers that read accurately form the tip are available but are usually used only in commercial cooking. The bimetallic thermometer is much more common and has some limitations for cooking and grilling. In any case, thermometers must be calibrated and tested for accuracy by placing them in an ice-water slurry. If the thermometer does not read 32 degrees, plus or minus 2, and it is adjustable, calibrate it; or if not, replace it.

Proper cooking temperatures must be remembered. Many USDA Cooperative Extension office make cooking temperature magnets for refrigerators and pocket reminders, and a reference is needed unless home cooks should have a working familiarity with them.

Its easy to under-cook foods when grilling out due to other problems such as  wind and other weather conditions, amount of flame, closeness to the flame,  amount of product cooked at once, and frequency of flipping.

Always remember to use separate plates and utensils for raw and cooked meat products.  Never place cooked food on a plate that held raw or under-cooked food.

Q:  What foods do not require special handling (cooling, cooking) at a picnic?

A:  Dry foods, or foods with high acidity are generally safely held at ambient temperature. Bread, ketchup, potato chips, pickles and relish are generally safe without temperature control.  Baked goods (without dairy or egg filling) and candies do not require refrigeration.  Many whole raw fruits and vegetables are safe at any temperature, w
hile unrefrigerated, sliced, cooked or processed vegetables can be risky unless they are acidic.  Cut melons require refrigeration, for example; and baked beans require hot or cold holding.  Certain cheeses require temperature control, soft cheese especially.  Commercial salad dressing and mayonnaise-based spreads are protected by acetic acid content and generally do not require strict temperature controls for safety; home made dressing or mayonnaise if made with dairy and/or eggs for example, would be more hazardous.  Remember:  cold foods should be kept cold and hot foods should be kept hot.  Perishable foods should generally not be left out for longer than two hours, and no longer than one hour on days that are 90 degrees or hotter.

Q:  With a potluck cookout, contributions of fresh fruit (grapes, apples, oranges) may or may not have been washed. What are you suggestions for staying safe in these instances?

A:  Unless the item is pre washed, such as some processed salad items, USDA recommends washing with plain water; however, studies have shown very little reduction of pathogens on the surface with the best washing.  In most cases, fruit is too acid to permit pathogen growth, so the haard relates mostly to cross-contamination during growing or distribution.  Some studies point to the use of safe surfactant washes as helpful.

Rather than accept donations of food from cooks whose food safety knowledge and habits are unknown, planners of events like church socials and potlucks should as best as possible ensure that persons donating foods acquire safe food handling information.

Catered events should only be handled by trained and qualified caterers under the authority of a health department.

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