Preliminary note: this technique works best in dry regions, and of course applies in hot environments. Otherwise, preservation is quite easy.
The summer heat always poses a conservation problem. Besides, it is the season when fruits and vegetables are produced in abundance. It gets difficult to consume the daily production right away, even with a small garden. Our ancestors have developed treasures of imagination and ingenuity to preserve their food without modern fridges: salting and pickling, jams, smoking, intentional fermentation (alcohols, lacto-fermentation…), and of course fighting in the meantime with heat (using grottos and deep cellars far from the ambiant heat, etc.).
In hot and dry countries, people have been using since the dawn of time systems to fight against the heat: ventilation shafts, water evaporation… which is the point that interests me right now.
Water has a very interesting physical property: its evaporation uses a lot of energy. Using energy means… refrigerating. For as far as humans records go, there are countless documents which show that humans have always used this property to cool water in hot weathers. Some Egyptian frescos show slaves fanning water pots, probably to accelerate water evaporation thus cooling them down.
Our body also takes advantage of this characteristic to cool itself, especially since the human race has lost its fur. By using heavy sweat, the body creates on top of the skin a thin layer of humidity which evaporates and thus regulates body temperature, by capturing the excess of energy from the body. Ingenious, isn’t it? Sweat also has other functions, but cooling down the body is an essential one.
The pot in the pot
In hot countries, people use a technique called “the pot in the pot”. A small waterproof pot is put inside a bigger, porous, pot (terra cotta…). Then sand is poured between the two pots, after that water is poured over the sand. The water penetrates the sand, runs through the outside, porous pot, which “sweats” that water, thus refrigerating itself just like the human skin. A smart Nigerian engineer even patented a technique, inspired from his grandmother’s ancestral habits.
The same principle has been perfected in India with a clay electric-less fridge, the mitticool:
This inspired me an idea. Building something out of clay is a no-go for me. I wanted to use something simple with objects around me to preserve some fruits and vegetables with the current hot and dry weather in my region. So I just put what I wanted to preserve in a case or crate, took a towel and soaked it with water. Then, I covered the case with my wet towel. As the towel dries up, the water on it evaporates and cools down the towel, which in turn cools down the contents of the case. The temperature drop is of several degrees, which helps preserving the contents.
Of course, this technique works best if the ambiant humidity is not so high. A little air circulation is also better to accelerate the evaporation thus the cooling. On the other hand, more moving and dry air dries the towel much faster, so it needs more frequent attention to wet it again. But if the towel is thick enough, wetting it twice a day is enough. Of course, the wetter it stays, the better, depending on how much effort you can put in this.
It is then possible to store in the case whatever needs to be preserved. It benefits from a lower temperature, and it is permanently kept moisturized, unlike the dry air of your fridge that sometimes dries up food too fast.
Mold and Fungus
Here comes a big, well know, problem. We all know what happens when something is kept consistently wet for a long time, especially in hot weathers. Mold and fungus develops rapidly. Besides, fruits and vegetables generally decay due to mold. So we need a way to fight back against the mold that will inevitably try to grow. We are literally making a Petri dish for mold here! They can grow both on the towel and on the organic matter inside the case.
A solution for the towel would be to change it regularly. But then you are going to spend a lot of time, energy, water, caring for the towel. And in the meantime, the vegetables will decay.
But there is a much more efficient and simple solution.
Sodium bicarbonate is inexpensive and abundant. It is the “Magic Powder”.
Mold and fungus literally hate sodium bicarbonate. This product can be even used at very low dosage to treat some diseases and plant molds like mildew. It is not really a fungicide, but it literally stops mold from growing.
So the trick is very simple: put some bicarbonate powder on your towel first, water it for the day, put it on the case, and you’re done! It will not only preserve the towel from mold, but it will also keep the mold away from the fruits and vegetables inside the case, due to the presence of the very basic pH of the bicarbonate around them. They will decay much slower. From my own experience, with ambiant temperatures around 30°C (86°F), you can preserve salad, zucchinis, and everything else for more than a week thanks to this trick.
I have found this documented nowhere, I have simply experimented it myself, it works great!
Preservation… is an Art
As final words, I would like to stress the fact that preserving food is not to be done randomly. Not everything should be kept together. Certain fruits produce ethylene which accelerates the decay of most vegetables, so you should keep those apart. Some fruits and vegetables really don’t like humidity so this trick is not for them. But this is another subject, on which you can find a lot of information on various websites.
Have you tried my trick? Please write your experience in the comments!