DRYING TECHNOLOGY
- 1. DRYING TECHNOLOGY BY ASSIST. PROF. Dr. BERCIYAL GOLDA. P
- 2. Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. Food drying is a method of food preservation in which food is dried (dehydrated or desiccated). Drying inhibits the growth of bacteria, yeasts, and mold through the removal of water. Dehydration has been used widely for this purpose since ancient times; the earliest known practice is 12,000 B.C. by inhabitants of the modern Middle East and Asia regions. Drying is a simple method for preserving food. Dried foods make great healthy and tasty snacks. They are good for lunches, travel, backpacking, hiking, and camping plus many other activities. Most types of foods can be dried. Drying is an ancient method of food preservation. INTRODUCTION
- 3. Food drying is one of the oldest methods of preserving food. Since drying reduces the moisture in foods making them lightweight and convenient to store, it can easily be used in place of other food preservation techniques. Drying food is simple, safe and easy to learn. The early American settlers practiced drying food using the natural forces of sun and wind and today, the use of technology has revolutionized this method of preserving food. With modern food dehydrators, foods such as fruit leathers, fruit chips, dried nuts and seeds and meat jerky, can all be dried year- round at home.
- 4. Drying is by far the most useful large scale operation method of keeping solid foods safe for long periods of time, and is of fundamental importance in most sectors of food processing. . Drying is defined as the application of heat under controlled conditions, to remove the water present in foods by evaporation to yield solid products. It differs from evaporation, which yields concentrated liquid products. The main purpose of drying is to extend the shelf-life of foods by reducing their in-water activity. Micro-organisms which cause food spoilage and decay and many of the enzymes which promote undesired changes in the chemical composition of the food are unable to grow, multiply or function in the absence of sufficient water Definitions
- 5. HowDryingPreservesFood Drying basically dehydrates or removes the moisture from the food and this simple action inhibits the growth of bacteria, mold and yeast. Moreover, it slows down the enzyme action without deactivating them. These factors ensure that food does not spoil easily and hence, makes drying an effective food preservation technique. Since drying removes the water from the food, the weight of the food item also reduces. This not only makes it lighter but also shrinks it in size. In order to use the food, all one has to do is add water to it. The best temperature to dry foods and preserve them is 140 deg F. However, for meats and poultry, the USDA Meat and Poultry Hotline recommends heating meat to 160 deg F and poultry to 165 deg F before starting the drying process. Once the heating is done, the dehydrator temperature should be consistent at 130 to 140 deg F. Using temperatures higher than this will result in cooking the food instead of drying it.
- 6. The food will cook on the outside and the moisture will remain trapped within. Drying is a slow process and one shouldn’t try and speed it up by raising the temperature. Another factor that helps with drying food is humidity. Since drying involves extracting the moisture from the food items and expelling it into the surrounding air, low humidity will help with the drying process. If the humidity is high, drying will be slower simply because the surrounding air would also be laden with moisture. By increasing the currents or flow of air, one can speed up the drying process. There are several ways of drying foods – in the sun, in an oven or in a commercial dehydrator. However, in either case, it is important to have the right temperature, air flow and level of humidity.