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Food Safety and Solar Cooking

Food 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.