Solar drying fruits and vegetables can help extend their shelf life.
It’s sad but unfortunately a very real fact that large quantities of fruits and vegetables have to be thrown out regularly. Why? Inadequate infrastructure and insufficient processing capacities makes it impossible to ensure that mass produced fruit and veg reach consumers on time. As a result, they begin to rot and waste away. However, that doesn’t have to be the case, for centuries we humans have been drying fruits and veg to preserve and increase their shelf life. It is a simple, yet effective method since moisture is the key player causing them to rot. By drying them out and drawing out the moisture, we can store them longer and keep their nutrients intact too.
And the best way to dry out fruits and vegetables is in the sun.
Solar drying for better nutrition
That’s because not only is it free, the sun shines in abundance for most of the year, is easily accessible and environment-friendly too.
The advantages of drying fruits and vegetables include:
> Retains nutritive value
> Extends their shelf life
> Seasonal fruits and vegetables can be accessed off-season
> Can be stored and used as rations during natural disasters
Traditional sun drying method
The traditional open drying process is performed by placing produce in trays or racks or directly on the ground and exposing them to the sun. However, areas that must deal with high temperatures and humidity often see a lot of spoilage. This method also leaves produce open to contamination from dust and other particulates. Non-uniform drying is another common occurrence.
Solar dryers: natural and forced convection
Solar drying can be practiced using both natural and forced convection solar dryers.
Natural air-drying in a bin drying system is slow and generally requires a larger amount of time. Drying results from forcing out unheated air and initial moisture content is normally limited to 22 to 24%.
A forced convection solar dryer on the other hand consists of an air heater, blower drying chamber, air distribution system and thermal storage system. The heated air is blown into the drying chamber by centrifugal blowers to handle large quantities of air. The drying chamber artificially creates the necessary radiation to reduce moisture. A thermal storage system can be arranged for collecting extra energy during daytime to take care of night operations. The forced circulation of air increases the rate of heat exchange between the air and the fruits or vegetables to be dried, thus forced convection dryers have better quality and time efficient results. Experiments have found that nutritional value and colour retention is higher with these solar drying systems.
Drying for longevity
Solar dryers are more economical compared to dryers that run on conventional fuel or electricity. The drying process is more hygienic and eco-friendly too. Solar drying systems also have low operation and maintenance costs and solar dryers last longer. A typical dryer can last 15-20 years with minimum maintenance. Without a doubt, solar dryers have become a popular choice to extend shelf life of fruits and vegetables without compromising on all the goodness they have to offer.
