Solar Cooking
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solar-cooked food

Solar cookers — when used properly — safely and conveniently cook all types of food, including meats, grains, legumes, vegetables and fruits. As with any cooking method, however, care should be taken when solar cooking to maintain food safety, particularly with meats, legumes and grains.

Cooking temperatures

Harmful food microbes, including bacteria and viruses, are killed when heated to 65°C (150°F).

thermometer

This is called pasteurization. Food cooks at 82°C (180°F) to 91°C (195°F), and is therefore free from disease-causing organisms when fully cooked. Simple solar cookers cook gently at temperatures just above these, so foods maintain moisture and nutrients, and rarely burn or overcook. Some solar cookers can cook at temperatures much higher than this.

With all cooking methods, certain bacteria produce heat-resistant spores that germinate after food has been cooked. Therefore, cooked food should be kept at temperatures above 52°C (125°F). If cooked food is allowed to drop to temperatures between 52°C (125°F) and 10°C (50°F) for a period of time, these bacteria can spoil the food and lead to food poisoning. Food that stays in this temperature range for more than four hours should be heated again to cooking temperatures before consumption. (Even after reheating there is still a risk of illness. If you are unsure you should discard the food.)

Main article: Food safety

Important considerations

  • Solar cookers generally require direct sunlight to function properly. Shadows, clouds and inclement weather limit their effectiveness, unless the cooker has incorporated some thermal mass to help hold the cooking temperature during brief cloudy periods. Solar cookers should be used on mostly sunny days, in locations where shadows are not a concern.
  • In most regions of the world there are a few months when simple solar cookers have limited usefulness, due to low solar radiation intensity. In general, you can solar cook when the length of your shadow on the ground is shorter than your height. This is an indicator that the sun is high enough in the sky to cook. Some solar cookers with tall rear reflectors however, are efficient enough to be used year-round.
  • You can typically solar cook two meals per day — a noontime meal and an evening meal. You typically cannot cook early in the morning or after sunset. The sun is most intense between 10:00 a.m. and 2:00 p.m., which is when breads and pastries should be baked if possible.
  • And, of course, always wash your hands before and after handling food, and use clean utensils and pots.

Eye safety

We periodically receive questions about solar cooking and eye safety. An eye specialist has explained to us that individuals exposed to direct or highly-reflected sunlight for long periods of time, such as sailors and fisherman, have an increased risk of developing cataracts as a result of receiving excess amounts of UV radiation. Most users of solar cookers, especially panel- and box-type cookers, spend relatively little time in the sun since food needs only be placed in the cooker and left, usually without any stirring, until finished. Also, the intensity of sunlight reflected by these types of cookers is somewhat less than that of direct sunlight. Certain curved concentrator-type cookers (parabolics) are of a little more concern since they are designed to multiply available solar radiation. And given the higher temperatures reached, stirring of the food is often required, resulting in more time spent near the cooker. With a little common sense, however, solar cookers can be used and enjoyed safely.

Below are some tips, sent in by Howard Boldt, for reducing the amount of sunlight that reaches your eyes while solar cooking. If you have any expertise in eye safety, or have any experiences to share, please contact Mr. Boldt and the SCI office.

Panel and box cookers

  • when inserting or removing food, place your body between the sun and the cooker, creating a shadow across the reflective area. Alternatively, rotate the cooker away from the sun briefly.

Curved concentrator cookers

  • when available, opt for a cooker with a low focal point (i.e. below the rim of the cooker)
  • when available, opt for a cooker with a device - such as rod on which the pot slides or a "swing arm" on which the pot sits - to allow for pot access without having to lean over the cooker.
  • use the cooker in a fenced area to prevent unwanted access. Alternatively, the cooker may be raised on a platform or used on a rooftop if feasible.

All cooker types

  • don't stare at the glare
  • if children will be in the vicinity, explain to them not to stare at the glare.
  • wear UV-blocking sunglasses if available

See The Importance of Eye Safety in Solar Cooking - Howard Boldt.

See Also

External links

Credits

This article uses material from Solar Cookers International's webpage http://solarcookers.org/basics/health.html.