Hilal Arslan BAYRAKCI Selcuk University, Karapinar Aydoganlar Vocational School, Food Processing Department   INTRODUCTION Dampening is one of the important processes that affect particularly flour quality, flour yield and energy consumption. Dampening can be defined as bringing the grain to be milled to the optimum water level and resting. The purpose for dampening of the grain is to make the physical properties of the grain suitable for milling by bringing the grain water to the optimum level and sometimes to increase the bread making quality of the flour (Keskinoglu, Elgun and Turker 2001). Depending especially on the hardness degree before milling the grain; dampening is the tempering or conditioning processes made for ensuring the optimum grain water level. Temperature and resting periods are quite important for the accomplishment of dampening process, grain’s absorption of water and the spread of water to the entire grain (Elgun and Ertugay, 1995). There are three factors that affect dampening in milling technology. These are dampening water, temperature and period (Elgun and Ertugay, 1995). Besides, the usage of heat in dampening both shortens the time and lowers down the energy consumption and ensures superiority in the flour quality by providing optimization on the physical properties of the grain (Keskinoglu, Elgun and Turker 2001). Dampening process includes two main stages. The first one is bringing the grain water to the optimum level. The second stage is the resting process necessary for the normal distribution functioning of the water in the grain (Elgun and Ertugay, 1995). 5% - 8% of water is given to the grain in dampening process. It is not possible to give the water like that amount at once especially in hard blending. Thus, the grain water is brought to the optimum level in two stages with wetting and transferring processes. This level varies from 15% and 17%. When these processes are taken as basis; the volume of the dampening silos doubles, dampening periods are extended, the number of mechanization units increases, investing, craftsmanship and maintenance costs increase (Yuksel and Elgun, 2013). 2. DAMPENING METHODS 2.1. Conventional Dampening (Cold Dampening) It is the dampening made at ambient temperature. Depending on the wheat properties and environment conditions; the resting period is considered to be between 24 and 72 hours. In this method; while the water absorption of the wheat is realized in a couple minutes, the spread of water through the grain requires a long period (Elgun and Ertugay, 1995). As the period for the spread of water through grain uniformly is long in this method, more dampening silo capacity is required. This situation is a disadvantage as it increases the costs (Ozkaya and Ozkaya, 2005). 2.2. Warm and Hot Dampening While 1-3 days are required for the spread and balancing of the grain that absorbs water in cold dampening, this period can be decreased to 1-1.5 hours in warm resting conditions at 30-46 °C. Despite that, a 24-hour period is suggested for the grain to gain optimum physical structure before the milling process (Elgun and Ertugay, 1995). The increase in the temperature shortens the period in which wheat is prepared for milling. When the temperature of the grain is increased, the grain enlarges and thus more water is absorbed with the opening of capillary tubes. It is claimed that the husk gains endurance and the endosperm softens with the temperature. In the studies made for this claim; it is determined that when one of the two wheat grains with the same moisture rate is heated at 27°C, it becomes more endurable and its endosperm is softer compared to the one heated at 21°C (Anonymous, 1990). In dampening; the water is slowly penetrated under the wheat husk. It is stated that it takes a long time for the water exchange between the husk layers at normal temperature, while the water absorption reaches maximum level with the temperature increase and in this case the wheat grain can absorb as much water as 40% of its own weight under normal conditions (Lockwood 1962). In the research made for warm dampening method; it is determined that the most proper endosperm softening is obtained at 45°C, patent flour yield increases, sieving is facilitated and there is a relatively decrease in the amounts of flour particles smaller than 75 microns (Kent 1990). The superiority of warm dampening method was firstly put forward by Grosse (1929). Wichser and Shelenberger (1949) determined the positive effect of warm dampening on absorption and spread of water in the grain and shortening of the dampening period. It is determined that endosperm is crisped too much and thus the milling is facilitated when the dampening water temperature increases to 45°C from 35°C (Cleve 1958). Hot dampening is realized with the modification of warm dampening. Apart from the warm dampening, the dampening stage can be increased to 60°C from 40°C in hot dampening. Although it is possible to increase the temperature to 70°C, the process period is very critical and dampening period is shorter at this temperature. As the gluten and bread making values of wheat are damaged in case of extreme temperatures, hot dampening is not applied much. This kind of dampening is especially used for the decrease of proteolytic activity. With this application, the proteolytic activity in the wheat can be decreased to a harmless level and the viscosity can be decreased in weak wheat (Elgun and Ertugay, 1995). Ozkaya (1986) states that the period of reaching saturation point can be related with the temperature even if the maximum water absorption of wheat does not change with the temperature and reports that the saturation point is reached in 48-72 hours at room temperature, in 24 hours at 27°C, in 8 hours at 40°C, in 2 hours at 60°C and in 40 minutes at 80°C. In a research made at a commercial mill; warm and cold dampening methods are compared and it is determined that the flour yield and patent flour efficiency is higher and the ash amount is lower in warm dampening method. This situation is reported as having a great importance for the country economy and milling (Turker and et al. 1997). 2.3. Vapor Dampening Promising short-time, easy to control and more uniformly dampening recently; vapor dampening was used firstly in Germany and then United States of America and Canada. Vapor dampening process includes the evaporation loss and releasing water that come out when the wheat temperature is increased generally with vapor and the cooling of wheat until the temperature required for the milling process. The temperature penetration into the grain with vapor application should be done in 20-30 seconds. This period is 3 minutes with dry air and radiator. The grain is also wetted (moisturized) with the vapor application. The temperature increases 10°C for 1% water condensation on the grain. When the vapor dampening is compared to the normal warm dampening; 1) It requires less energy. 2) The quality is better or if it is equal, flour yield is higher. 3) Milling, purification and sieving processes are realized easily. 4) Dampening is realized in a shorter time. Normally, vapor application does not exceed 20-30 seconds; however the gluten is not damaged when the period is extended to 45-60 seconds. But, there can be a decrease in the alpha amylase activity in this kind of wheat. For that reason, it should be fortified (Elgun and Ertugay, 1995). 2.4. Microwave Dampening Microwave is used in the food industry for the processes of cooking, defrosting, tempering, drying, freeze-drying, pasteurization, sterilization, cooking and heating in the oven. There are many studies on the usage of microwaves in the grain and cereals industry. In the research by Elgun and Turker (1995) on the separation of husk and endosperm of the grain and flour properties in the microwave applied wheat dampening; Bezostaya-1 and Gerek’79 wheat grains were used. Bezostaya-1 and Gerek’79 were dampened with water absorption. The dampened wheat samples were milled by applying microwave process and without that application. It is seen that microwave application increases the flour yield of the two grains but decreases the ash amount. However, the yield increase occurs together with the ash increase. As it means obtaining more flour from unit wheat, it can make an important economic contribution. The increase of flour yield and non-increase of ash amount with microwave application is a sign that husk and endosperm separation is better in microwave process. When the results of the research are compared with the witness sample, the following issues are determined; 1) The flour yield increased. 2) Despite the increase in flour yield, ash amount decreased. 3) The amount of dry extract increased. 4) Bread volume increased. All of these results show that microwave application increases the separation of husk-endosperm. This situation creates an advantage in the milling industry in terms of white flour yield. Bayrakci (2008) researched the milling process in laboratory environment and the effect of microwave application on bread making quality by optimizing the microwave radiation and heating effect. For this purpose; two wetted different wheat varieties were dampened at different microwave heating levels and the change in “milling, flour, dough and bread quality” parameters by being compared to the samples that were dampened with the conventional style. As a result; the ash amount of the samples obtained from the wheat dampened with microwave application was found quite lower than the witness sample and the yield values increased 10% compared to the witness sample. In another research by Walde and et al. (2002); wheat samples with different moisture contents were dried in a household microwave oven at periods ranging from 15 to 150 seconds and then milled. It is determined that the sample that was applied microwave application for 120 seconds is more crispy and requires less milling energy compared to the control sample. Doty and Baker (1977) applied microwave energy (625 watt) on hard red winter wheat for 450 seconds in a closed system before milling process. The temperatures of the conditioned samples were kept between 22°C (0 seconds) and 105°C (450 seconds) and positive results were obtained. It was determined that according to the analysis results of flour and bread; the microwave applications made over 270 seconds adversely affect the important quality parameters physicochemically. 2.5. Dampening with Ultrasound Application Ultrasound application is used commonly in many fields of food industry such as homogenization, crystallization, purification, extraction, foam breaking, degassing, drying, blending, etc. (Bhaskaracharya and et al., 2009; Brennan, 2006; Ercan and Soysal, 2011). There is a quite limited application field in grain milling. It is used in drying and sieving processes in order for increasing the efficiency (Mason and et al., 1996; Brennan, 2006; Ensminger, 1988; Frias and et al., 2010) and in the malt production for the acceleration of wetting and germination processes (Yaldagard and et al., 2008). In a research by Yuksel and Elgun (2013) in which the effect of ultrasound application on the water absorption of the grain during the wetting of the wheat; they applied ultrasound application on wheat samples having different grain hardness (45, 65 and 75%) with 4 different amplitude levels [0% (witness), 20, 60 and 100] at normal conditions in wetting phase at 3 different periods (1, 2 and 3 minutes). The results of the research were compared to the normal wetting process. Depending on the grain hardness, more water absorption around 7-8% was determined compared to the moisture content of the dry grain. Wetting process with ultrasound application increased the grain’s absorption and spread of water. With these data; promising results were found for the decreasing the two-staged dampening especially in hard wheat milling diagrams to one stage with the wetting method of ultrasound application. On the other hand; it was understood that the wheat wetting periods can be shortened in malt and wet milling industries with the usage of ultrasound application. As a vibration mixer, Vibronet is one of the dampening machines that draw attention in the market recently. Wheat and water are taken into a vertical chamber and mixed by using vibration energy. This process can provide decrease in the dampening period and energy consumption compared to the conventional dampening methods. The vibration energy ensures the spread of water from the outer layer of the wheat to other sections of the grain with fast absorption (Fowler, 2013). The principle of this patented method is based on ensuring the encircling of the grain with water in film form by destroying the surface tension of water molecules. Thus, the dampening water is penetrated into the husk and the outer layers of endosperm equally (www.tetamuh.com). 3. CONLUSION Dampening is the preparation stage of the grain for milling process in the flour industry. After the importance of dampening was understood, studies concentrated on new methods and technologies and they still continue to be conducted. These studies will also continue to light the way for the development of new technologies especially for millers after the production costs are calculated.