Grinding characteristics and heat of combustion of sprouted wheat
Pre-harvest sprouting is the premature germination of cereal seeds so that the embryo starts growing while still on the head in the field. Grain germination before the harvest is a serious problem in many wheat-growing areas of the world. The grain and flour quality parameters impacted by pre-harvest sprouting are strongly related with climatic variables and soil water condition. This process especially occurs when wet conditions delay harvest. Spouted seed is usually inadequate for flour productions. Products made of sprouted flour are generally unacceptable to producers and consumers. Moreover, it is also often inadequate as feed because microbiological contamination. However, it seems that such kind of waste grain can be utilized for energetic purposes. The aim of the present work was to study the grinding process of sprouted wheat. The heat of combustion of sprouted grain and sound grains was also determined. Three-day germinated kernels of three wheat varieties were used for investigation. After germination the wheat kernels were dried at 40°C by using an air dryer to obtain the same moisture as that of the grain before sprouting (14.0% w.b.). The sound kernels were used as a control sample. The sprouted and the sound samples of grain were ground by using the knife mill MG-200. The results showed that the sprouting of wheat had a significant influence on the grinding process, both on the particle size distribution and grinding energy requirements. The sprouting caused a decrease in the average particle size and value of specific grinding energy in all cultivars. The values of specific grinding energy ranged average from 21.6 kJ·kg-1 to 23.6 for kJ·kg-1 fore sprouted and sound kernels, respectively. The heat of combustion of sprouted grain was only slightly lower value of this parameter obtained for sound grain and ranged from 15.9 to 16.5 MJ/kg.