Food dehydrator

Afood dehydratoris a device that removes moisture from food to aid in itspreservation.Food dryingis a method of preservingfruit,vegetablesandmeatsthat has been practiced since antiquity.
Most modern food dehydrators are low-powerconvection ovensthat use heatedair flowtoreduce the water contentof foods.  The water content of food is usually very high, typically 80–95% for various fruits and vegetables and 50–75% for various meats.  Removing moisture from food restrains variousbacteriafrom growing and spoiling food, as well as dramatically reducing the weight and often the volume of the food, making it easier to store.  Thus, food dehydrators are used to preserve and extend theshelf lifeof various foods.
Food dehydrators requireheat sourcessuch assolar energy,electric powerorbiofuel.They vary in size from large-scale dehydration projectstodo-it-yourselfprojects or commercially sold appliances for domestic use.  A commercial food dehydrator's basic parts usually consist of aheating element, anelectric fan, air vents which allow air to circulate, and food trays to lay food upon.  As shown on the right, the trays most commonly have slits to provide more surface area between the food and the air. A dehydrator's heating element, fans and vents simultaneously work to direct hot air over the food, accelerate surfaceevaporation, and warm the food to also release moisture from its interior.  This process continues until the food is dried to a substantially lower water content, usually less than 20%.
Most foods are dehydrated at 130 °F (54 °C), although meats being made intojerkyshould be dehydrated at a higher temperature of 155 °F (68 °C)—or preheated to that temperature—to guard againstpathogensthat may already be in the meat. These temperatures are similar to those used inpasteurization, and achieve similar effects.  The key to successful food dehydration is the application of a constant temperature and adequate air flow.  Too high a temperature or too low of airflow can cause hardened foods: food that is hard and dry on the outside, but moist, and therefore vulnerable to spoiling, on the inside.
Solar food drying involves using asolar dryerdesigned and built specifically for this purpose.  Solar drying is distinctly different from open-air "sun drying," a simple technique used for thousands of years.  A good solar food dryer may dry food much faster than some air dryers.  Some solar driers can achieve higher food drying temperatures than some air driers.  However, direct sun drying can chemically alter some foods, making them less appetizing.
Food drying primarily requires heat, and solar radiation can easily be converted to heat. Transparent or translucent glazing allows sunlight to enter an enclosed chamber, which converts it to heat when it strikes a dark interior surface. Airflow is typically achieved with natural convection (warm air rises). Adjustable venting allows airflow and temperature to be controlled.
Solar food drying is effective and practical in most of the populated places of the world.A general rule is that, if you can grow a successful vegetable garden, then there is enough solar energy to dry the food you produce (some overcast, northern maritime climates are the exception).
Some solar food dryer designs employ a separate solar collector to generate the heated air, which is then directed into a food chamber or cabinet. This type of solar food dehydrator is called an indirect solar dryer.Other designs combine the collector and food cabinet and allow direct heating of food (these are called direct solar dryers).It is said that the indirect dryers allow much better drying, but the downside is their larger size. Backup electric heating can be incorporated into some solar food dehydrators to provide an alternative heat source if the weather changes.
Solar food dehydrators are often cited as viable tools in the search for agriculturalsustainabilityandfood security.