Using a Solar Drying

Assembly Procedure

• Insert the mesh trays into the dryer
• Angle the mechanism so that is faces the sun and is out of any shadows
• The dryer should be installed in a dry, dust free place
• Wherever possible, concrete floor is recommended

Processing Food and Hygiene

• Cleanliness of the machine
  • Trays and interior must be cleaned between each use with soap and a soft cloth. The surrounding area should be as clean as possible
  • Personal cleanliness is essential. Wash hands with soap before handling the goods to be dried
  • The processing place and equipment must also be cleaned with soap and water (cutting, peeling, slicing and washing areas and knives, cutting boards etc)
  • Depending on product type, foods must be peeled or sliced, have stems removed or have leaves removed *see table for more information

Procedure to Load Trays

• Trays should be cleaned with soapy water and a soft cloth before use. Excess water should be drained before loading.
• 70-80% of the trays should be loaded with goods. The remaining 30-20% needs to allow space for air to flow up the dryer.
• Weigh 2-3 pieces of fresh product before it is loaded. Calculate the weight of the product
• Load products in the morning as early as possible so that goods can be dried gradually throughout the day. Depending on the product, it is ideal to unload the products during the afternoon to limit the amount of moisture reabsorbed by the product.
• Products that are not fully dryed in a day should be removed before sundown and kept in an airtight container or plastic bag. These products should be reloaded onto the trays the following morning until the drying process is complete.
• In case the goods are sticky (pineapples, mangos etc.) they should be turned every 2-3 hours. This will also help speed up the drying process.
• After the standard drying time has elapsed, calculate the water content of the sample. If it is between 10-15%, the product is ready to be taken out of the dryer. If the water content is greater than the recommended value, place back in the dryer and continuous check on the products until the desired water content is achieved.
• In the last stage of drying, quality should be checked by look and touch.
• Once goods are removed from the dryer, they need 2-3 hours to cool.
• Once goods are cooled, they can be bagged and sealed in high grade plastic bags or containers.

(mass of initial sample - mass of dried sample)

Water content = ---------------------------------------------------------- x 100

mass of initial sample

Factors Affecting Solar Drying

• Solar drying isn’t always exact, and drying times can vary according to a number of factors including:
  • The nature of the material: shape and moisture equilibrium
  • Slices and size of cuts: thinner and smaller slices will dry faster
  • Ambient temperature and humidity: hotter and dryer days will dry foods faster, while cooler and humid days can slow down the drying process
  • Air flow rate: temperature and wind will affect the speed of airflow through the dryer, thus affecting drying time