Drying or dehydration is the removal of substances that can evaporate, such as water or moister, in order to slow down or stop the growth of microorganisms or chemical reactions.
During this process, there are a number of changes in the physical and chemical properties of the dried product. These may include features such as shape, hardness, color, aroma, taste and nutritional value. In conventional drying methods, due to temperature difference between the surface and the cold interior,heat is transferred by stages through the surface of the dried material towards the interior. This situation causes the heat between the surfaces of the product to be unequally distributed.But, the problem of heat transfer in conventional drying methods has been solved in the microwave drying process. Advantages of combinational drying with microwaves include shorter drying times, improved product quality and flexibility in producing a wide variety of dried products. Thus,the original flavor can be preserved. Depending on the short drying time, the heat loss is also minimized..These can be applied to foods; particularly to fruits and vegetables. Fruit drying is the process of removing moisture. Fresh fruits or vegetables last for few days; if we use the drying methods for fruit preservation then they can be stored for months or even years. The benefit of drying fruits and vegetables is not only to preserve crops as food but also reduce package and transport cost in terms of weight and volume, while offering the possibility of adding value to harvested goods. Dried fruits are highly nutritious.One piece of dried fruit contains about the same amount of nutrients as the fresh fruit, but condensed in a much smaller package.By weight, dried fruit contains up to 3.5 times the fiber, vitamins and minerals of fresh fruit.
Therefore, one serve can provide a large percentage of the daily recommended intake of many vitamins and minerals. One of the major benefits of dried fruits is that in small quantities they concentrate a large amount of nutrients, even 4 times more than when they are fresh fruits.This is due to the reduction in size. If we may include them in our daily diet we can be assured the absorption of important nutrients. One of the most common and easy ways is to consume these foods as a snack.Because they do not have added sugar, nor any other type of additives which makes them an excellent option for daily life.Moreover,dried apples and pineapples are fruits that have many nutrients that help us increase the defenses in our body, help the skin have a better appearance, helps maintain metabolism and are highly recommended for people suffering from hypertension.These highly recommended fruits are easily consumable snacks that can provide a healthy life. For example, dry apple contains many fibers and is known worldwide in terms of its natural laxative properties, promotes the functioning of the intestines and increases energy due to the fructose it contains. This fruit is ideal to combine in the morning with cornflakes, or you can prepare yogurt with banana and prunes, or even combine with other dried fruit to get more flavor. The dried pineapple is another ideal fruit to lose weight because it is diuretic, improves digestion, cleanses the skin, contains fiber and minerals like magnesium, iron, and potassium; also it contains antioxidants, among other vitamins. Dried pineapple helps digestive problems because it contains fibers that are like a sponge in the intestine and clean your organism, remedying constipation and eliminating toxic elements that could cause damage to our body.
Table 1. Comparison of convective and microwave drying of grape
Microwave Drying Of Apple
Dried fruits are widely used as ingredients in many food formulations such as pastry, confectionery products, ice cream, frozen desserts and yoghurt. Dried apples are an important raw material for many food products among other dry fruits. The drying process was progressed through two stages.in the first stage the samples were put in a microwave oven and in this period, approximately 55% of the water was removed. After that, at the second stage, the apple samples were put in forced draft oven to reach the final moisture content. 
One of the main benefits of dehydrated apples is their dietary fiber content. A half-cup serving of the dried fruit contains 3.7 grams of dietary fiber. If you follow a 2,000-calorie diet, the snack provides 13 percent of your daily fiber according to the Colorado State University research. It also slows digestion, preventing blood sugar spikes that leave you tired and hungry shortly after your meal.
Dried apples also provide a source of beneficial vitamins for your health. They contain several B vitamins that collectively support your metabolism and they feed your liver and skin.
According to the Linus Pauling Institute, a half cup of beverage contains about 6 percent of daily B-6 vitamin consumption and 3 percent of daily B-5 vitamin intake. Both vitamins help to build neurotransmitters, which are chemicals needed for brain function.
Dried apples are beneficial because of their mineral content. Potassium, another mineral that is useful for the health of the nervous and brain functions, is found in a lot of dry apples. Each half-cup serving contains 4 percent of your daily recommended intake of potassium. In the dried apples there is a small amount of iron and we use it to make new red blood cells.So, our tissues can get a fresh supply of oxygen from your bloodstream.