THE INFLUNCE OF WHEAT HARDNESS ON ENERGY CONSUMPTION DURING THE WHEAT MILLING

Wheat is generally used for a food after converting grain components into different degrees of flour. The perfect milling operation needs to get enough knowledge about kernel mechanical properties and mainly hardness, to estimate correctly its effect on grinding performance. This study determined the influence of wheat hardness on milling energy and efficiency. The results showed great effect of wheat hardness on milling performance. The lowest values of specific energy were recorded in the case of cultivar Katoda. This cultivar is characterised by the lowest value of hardness index. The study indicates that, it is possible to select cultivars with low specific energy and high efficiency during milling, which in effect will cause a reduction of production costs. INTRODUCTION Since the dawn of agriculture, wheat has been the major source of food and calories for mankind worldwide (Krasileva, Vasquez-Gross, Howell, Bailey, Paraiso, Clissold, Simmonds, Ramirez-Gonzalez, Wang, Borrill, Fosker, 2017). It is a leading source of protein in a human diet for its high protein content (Bhat, Wani, Hamdani, Gani, Masoodi, 2016). Examining the mechanical properties of wheat grain shows the way to optimize the machine designs and helps us determine the forces endured by wheat grains through milling process and leads to advance improvements make possible for us to drive an innovation process, (Ahmed, Nadulski, Kobus, Zawiślak, 2015). Grinding wheat is one of the oldest techniques of food processing, (Hourston, Ignatz, Reith, Leubner-Metzger, Steinbrecher, 2017), in which wheat endosperm is gradually grinded to a particular size range of flour through a progressive size-reduction process, (Patwa, Malcolm, Wilson, Ambrose 2014). Although several types of milling machines are used now, but, the most common is roller mill which grind by share and compression forces to get wide reduction of particle size (Dziki, 2011). The energy consumption through wheat milling operation has attracted a lot of scientist attentions. Consuming energy during wheat grinding operation is the highest in whole cereal industry processing (Dziki, Laskowski, 2005). Grinding energy and flour yield are affected extensively by tempering [Warechowska, 2014) and hardness (Dziki, Cacak-Pietrzak, Miś, Jończyk, Gawlik-Dziki, 2014). On the other hand, energy consumption of grain grinding depends mainly on kernel hardness, which defined as the ratio of rupture force to the deformation at the rupture point of the grain that achieved by Instron machine test (Başlar, Kalkan, Kara, Ertugay, 2012), and influenced by different factors such as moisture content (Clarke, Rottger, 2016). The energy consumption and final product specification are the main indicators for both producer and consumer (Raigar, Prabhakar, Srivastav, 2017). Thus, specific grinding energy in the milling operation is calculated as the ratio of the grinding energy to the mass of the wheat used to grind (Dziki, Laskowski, 2010). The milling efficiency is an important indicator to define wheat milling performance, (Warechowska, Warechowski, Skibniewska, Siemianowska, Tyburski, Aljewicz, 2016).The values of milling efficiency index are decrease with medium-hard wheat, but increase with hard wheat but