Food Safety: Packed Lunch

The featured abstract, from the respected journal, Pediatrics, explores the condition of packed lunches at a pre-school.  There is no reason to think that other school environments are any different.  Despite a parent’s best efforts at keeping a child’s lunch from spoiling and causing food-related illnesses, such incidents still occur because of inattentive food handling at school.  Malevolence is not usually a factor.

The University of Texas initiated a study into the conditions at schools that can lead to food-borne pathogenic illnesses, and found that temperature control is the prime concern.  Ninety percent of kids’ packed lunches reach unsafe zones. Even with multiple ice packs, “…the majority of lunch items…were at unsafe temperatures.”  As is the case with all health-related measures, “Education of parents and the public must be focused on methods of packing lunches that allow the food to remain in the safe temperature zone to prevent foodborne illnesses.” (Almansour. 2011)

The “danger zone” for foods lies between 40° F. and 140° F.  Therefore, foods kept outside the “zone” are subject to the growth of pathogenic micro-organisms, whether at school, on a picnic, in the backyard, or in the kitchen.  A mantra that has been embraced long ago is that food should not be kept out of refrigeration longer than two hours.  Luncheon meats, smoked meats, and other cured comestibles are not an exception.  If the ambient temperature is higher than 90° F., the limit is one hour.  Unless the classroom has a refrigerator, this is practically impossible to do at school.  Note that the insulated bags we use to pack our kids’ lunches can rebound inside a refrigerator and prevent the cold from getting to the food.

Of course, Mom or Dad has to start with clean ingredients prepared on a clean surface, using clean hands and clean implements.  The CDC holds that only 3% of food contamination can be attributed to the farm.  The other 97% occurs between there and the kitchen.  (Alliance for Food and Farmng.  2010)  Including an ice source is imperative if you know the lunch will be kept at room temperature, such as within a middle-school locker, where teachers have found last month’s French fries after the mephitis rendered the neighboring crowd semi-conscious.  If the timing can be figured out, it’s O.K. to freeze those items that can be frozen without compromising their sensory quality.  Dressings like mayonnaise, and delicate items like tomatoes, are not in this group.  Peanut butter and jelly, and whole fruits and vegetables need not be cold.

If salad ingredients are part of the repast, especially lettuce, it’s vital that they be kept below 39° F. or so, lest they start to show a significant decline in visual quality as well as in safety.  However, even if it looks good, lettuce can harbor and encourage proliferation of E. coli, a dastardly micro-organism with a reputation worse than Blackbeard’s. By the way, this bacterium can thrive even on the pre-washed, ready-to-eat greens you bring directly home from the supermarket.  (Luo. 2010)  Wash them anyway. Plain water works, but a 50-50 mix with hydrogen peroxide can set the mind at ease. Peroxide reverts to plain water after exposure to light and air. That’s why it comes in an opaque brown bottle.

Smaller amounts of food in shallow containers are easiest to handle. You really don’t want to be sorting leftovers after they’ve been on the bus ride home.  Getting the containers back is another story.

Pediatrics 2011; 128; peds.2010-2885 Published online August 8, 2011 (doi: 10.1542/peds.2010-2885) Temperature of Foods Sent by Parents of Preschool-aged Children Fawaz D. Almansour, MS, Sara J. Sweitzer, PhD, RD, LD, Allison A. Magness, BS, Eric E. Calloway, BS, Michael R. McAllaster, BS, Cynthia R. Roberts-Gray, PhD, Deanna M. Hoelscher, PhD, RD, LD, CNS, Margaret E. Briley, PhD, RD, LD

J Food Sci. 2010 Sep;75(7):M390-7. Effect of storage temperature and duration on the behavior of Escherichia coli O157:H7 on packaged fresh-cut salad containing romaine and iceberg lettuce. Luo Y, He Q, McEvoy JL.