Drying, particularly sun-drying, is among the oldest methods of food preservation utilized by the human species. It works by reducing moisture content in a food through the process of heating, which in turn destroys microorganisms including yeast, bacteria and mould.
Basically, the process works by reducing the moisture content in a food, and since moisture is among the factors that trigger food spoilage, this method reduces the probability of a food’s deterioration.
Among the common methods of drying encompass:
- Air drying– It is currently the most common drying method due to its efficiency and affordability.
- Sun-drying– It is the oldest and most cost-effective drying method. It is suitable for drying fruits and vegetables like berries, apricots and tomatoes.
- Freeze drying– It involves the use of low temperatures and low pressure to achieve sublimation that allows the drying of food products. This method is known to maintain the taste and texture of foods.
- Contact drying– This drying method involves the drying of foods by placing them in close contact with the heated walls of rotating drums(in machines). The main aim of this method is usually to allow the uniform drying of foods.
- Steam drying-This method uses superheated steam to dry foods. It enables foods to achieve enhanced texture i.e. they become crunchier.
The drying method and nutrient value of a food
Depending on the drying method used, a food’s texture, taste , and nutrient value can be affected. It is essentially proper that the drying method selected has the least likelihood of deteriorating a food’s quality to ensure that the original form of a food is not greatly altered.
Dried foods, especially those sun-dried, retain their nutrient value including their protein and mineral content. Generally, drying food does not result in any significant nutrient losses, except for vitamin C and occasionally vitamin A. The loss of these vitamins can however be minimized by drying in the absence of oxygen. Depending on the method of drying, a food’s texture can be altered.
Factors that affect the drying of foods
The method of drying selected
Size of food pieces-some pieces contain more moisture in them than others thus they take longer to completely dry.
The moisture contained in a food-some foods including cabbage may contain higher water content hence take longer to achieve optimal drying.
Examples of foods that are dried for preservation
- Fruits e.g. apricots, figs , grapes , dates, peaches etc
- Meat, fish, poultry, lamb etc
- Vegetables e.g. carrots, mushrooms, potatoes, maize, beans, peas etc.
Advantages of the drying method
- Decreases moisture content– thus slowing down enzymatic activity and hindering microbial activity.
- Reduces the bulk of a food -hence allowing easy transportation, distribution and storage etc.
- Extends the shelf-life of a food item– by reducing water activity, in turn preventing microorganisms.
- This food preservation method can be applied to a vast majority of foods -including meats, fish, vegetables, fruits etc
- It is safe– the method is safe as no chemicals that can cause harm are added .
Ways to consume dried foods
Once the food is ready for consumption, you add some water to it when cooking to restore it to its initial form. Alternatively, the food can be grinded or consumed in its dried form.
Shelf-life of dried foods
Dried foods can last up to several months to an year; although, if a food is not properly dried, it will last for a shorter duration compared to a similar food that is well- dried.
In drier areas, foods are likely to last longer than in humid areas, hence more stringent measures have to be taken into account when handling the drying of foods in humid areas. To last even longer, dried foods should be enclosed into airtight bags, and stored in a dry place without any light. This will allow the food to remain preserved for longer. With all other factors maintained including temperatures, light and air conditions, a well-dried food can be preserved for several months to an year.