I put a top round roast in the solar oven yesterday. I had just brought it from the store. It was after Noon before I put it in the pot & into the oven to cook.
The sun was clear & bright. This is November, however, so the sun is lower in the sky than in summer & also goes down much sooner. I figured I had about 3 hours to get it up to safe temperature.
Safe temperature is when the meat gets hot enough to retard bacterial growth. Solar cooking with the kinds of ovens I use is not very high heat, only about 180F. It makes up for heat with time.
In this case I was counting on enough heat to retard bacterial growth, not necessarily to cook the roast through. When the sun goes down it gets cold enough here in the desert, as cold as your refrigerator, to keep the meat safe through the night.
Next morning the sun comes up bright & clear. The meat heats up & cooking resumes all day until the roast is fully cooked & ready to eat.
Problems arise when the raw meat is put in the solar oven & then clouds appear, covering the sun. If the meat heats up enough to encourage bacterial growth but not enough to kill or retard it, food safety is an issue. Then it is time to put the pot on my propane stove or on hot coals of my campfire to bring it to sufficient temperature for sufficient time. This usually results in searing the meat on both sides. It is vitally important to NOT LIFT THE POT LID once the meat has been well heated. Lifting the pot lid admits a new assortment of potential bacteria.
Once well heated the pot can be put back in the solar oven for overnight. If the sun is hot and bright the next day, let it cook with the sun as usual. If not, it goes back on the fire to completely cook & be eaten–if it smells and tastes ok. It ought to, since I have handled any potential food safety issues before they got started.
The most important lesson to learn while solar cooking is to only lift the pot lid when you know you have enough time for the sun to reheat the food sufficiently. So you eat at Noon or shortly thereafter, opening the pot to get what you wish to eat, then replacing it in the solar oven. Do not touch it for the rest of the day unless you plan to eat all the food left in the pot at the end of the day.
In my case, while camping, this sometimes results in food becoming over cooked. I’d rather have over cooked food than have it spoil!
In the seven years I’ve been solar cooking nearly every day, I’ve only lost food to spoilage a half dozen times. I’ve learned that I probably cannot cook even a small turkey for Thanksgiving. It is just too cloudy at that time of year, even in sunny Arizona! Also the bulk of the bird is just too much to handle during the short days even with sun. Almost any other time of year such cooking would work fine. But not Nov.-Feb.
That’s ok! Pork chops, hamburger, steak, chicken, stews & soups all do fine cooking with the sun all winter.
A word about vegetables. Fresh broccoli, carrots, Brussels sprouts & even potatoes seem to take a lot of time to get tender. I do not cook them in the same pot as the meat. They cook separately in their own pot. They are subject to the same food safety issues as the meat.