Miller Magazine Issue: 132 December 2020

60 COVER STORY MILLER / december 2020 traction and lower ash content are among of the advan- tages of these methods. TEMPERING BINS As described earlier, after water adding to wheat, it is left to rest in tempering bins to enable the water to penetrate into wheat kernel. Steel or concrete bins can be used for tempering. The tempering bins should be designed with multiple outlets have openings with a minimum diameter of about 155 mm to secure a mass flow of tempered wheat where the earlier tempered wheat leaves the bin first that can be described as FIFO “first in, first out”. Tempering bins capacity depends on resting time and milling system capacity. Tempering bins capacity can be calculated by following equation: MULTIPLE STAGE TEMPERING Multiple stage tempering should be used if the mill processes different type of wheat especially if the wheat types are significantly different in hardness or size. To have the wheat and blended after first or second condi- tioning process. In these cases, the soft and hard wheat or big and small kernels wheat have to tempered for dif- ferent periods so that should be conditioned separately and then blended before milling. Produced flour color improving and reducing its ash content can be among of advantages of multiple stage tempering. In the second conditioning stage the wheat can be scoured and aspirated to remove partially the kernel barn. Tempering Temperature Tempering temperature affects water penetration rate into wheat kernel. Optimum temperature of wheat is in the range 23-27 °C. To achieve optimum conditioning in cold weather the used water temperature should not be below 25 °C. During the tempering period there is a natural rise of 4-6 °C in wheat temperature. Tempering Time The tempering time is related by the rate of water penetrating into kernel which depends on the damping method, the initial moisture content, kernel hardness, and kernel temperature. Damping with low-speed mixer can take up to 72 hours, while 7 to 12 hours using the intensive damp- ener. Generally, hard wheat types require long tempering time to achieve optimum water dispersion all over the kernel. Although, high moisture wheat requires lower amount of water than the dry one, the rate of water penetration is faster. In other words, lower initial moisture content, tempering time should be longer.