Food Safety and Solar Cooking
safety for food cooked by any method requires meeting specific rigid conditions.
Cooked food at temperatures between 125° F and 50° F (52° C - 10° C) can grow harmful bacteria. This temperature range
is known as the danger zone. To protect against food poisoning, microbiologists
and home economists strongly recommend that food be kept either above or below
these temperatures. These precautions are the same whether food is cooked with
gas, electricity, microwaves, wood fire, or solar heat as well as foods cooked
by retained heat, crock pot, barbecue pit or any other method. In cooked food
held at room temperature, there is a chance of Bacillus cereus food poisoning, a
major intestinal illness. Worse, if the food is not thoroughly reheated before
consumption, there is a chance of deadly botulism poisoning or salmonella. Even
if it is reheated, when cooked food has been in the danger zone for three to
four hours, there remains a risk of food poisoning in solar cooked food as in
food cooked by any other method.
It has been carefully documented with regard
to solar box cookers that it is safe to place raw refrigerated or frozen food,
even chicken or other meat, in a solar box cooker (SBC) in the morning several hours before the
sun begins to cook it. Refrigerated food placed in an SBC remains sufficiently
cold until the sun starts to heat the SBC. Once the full sun is on the oven, the
heating of food proceeds quickly enough so that there is no danger of food
poisoning. Uncooked grains, beans and other dried raw foods can also be placed
in an SBC in advance. Both of these methods facilitate absentee cooking.
There are three main points at which caution
is required: it is dangerous to keep cooked food more than three or four hours
in an unheated or cooling SBC unless both the SBC and food have been cooled
rather quickly to below 50° F (10° C) in which case the SBC is serving as a cool
box; it is dangerous to let cooked food remain overnight in an SBC unless it is
likewise cooled; and it is dangerous for food to partially cook and then remain
warm in the SBC when temperatures are not sustained as might occur on a poor
solar cooking day, at the end of the day or when clouds move in. Cooked or
partially cooked food should either be cooled to below 50° F (10° C) or cooking
should be finished with an alternate fuel. If food has remained in the
temperature danger zone for 3 to 4 hours it should be considered spoiled and
should be discarded. Reheating the food does not correct the problem as heat
does not inactivate all toxins.
Food does not have to be visibly spoiled in
order to be toxic and cause illness evidenced by nausea, vomiting and diarrhea.
Even if food has not been at the incubating temperatures of the danger zone for
the full 3 to 4 hours, absolutely discard food that is bubbling, foaming, has a
bad smell, is becoming discolored, or gives any other indication of spoilage.
Discard it out of reach of animals and children and thoroughly wash the pot.
Discard it without tasting it as even small amounts can make an adult very sick.
If temperatures below 50° F (10° C) cannot be
obtained, it is still valuable to drop food temperatures as low as possible and
as quickly as possible rather than allowing food to remain warm since bacteria
grow more slowly at lower temperatures.
An alternative method of holding cooked food is to reliably maintain the temperature of the entire food mass above 125° F (53° C). This can be achieved by first heating the food to boiling, simmering for a few minutes to allow heat to penetrate to the center of each particle and for a pocket of steam to collect under the lid. Then proceed as for retained heat cooking. This provides the level of temperature needed throughout the food, whereas leaving a pot of food on a very small flame may allow food at the edges to remain in the danger zone. Where neither of these methods can be used, it is best to cook amounts of food that will be consumed in one meal relatively soon after being cooked.
This article was excerpted from The
Expanding World of Solar Box Cooking, by Barbara Kerr.