Improving nutritive value of broken wheat kernels by extrusion

Abstract

In the technological process of either trade or seed wheat cleaning before drying and storage, organic and inorganic impurities are separated. The amount of separated impurities depends on various factors and can range up to several percent. In the structure of organic impurities, beside broken, shrunken and other cereals kernels, also weed seeds, moldy and smutty grains are present. According to the Serbian Chamber of Commerce, last year 2.093.198 tons of wheat is gathered form 492.989 hectares. In case 2-3% of wheat organic impurities are valorized as feed, this quantity amounts between 42 and 63 thousand tons. It is also important to emphasize that by extrusion process this waste material can be turned into nutritionally and hygiene safe product. Prior extrusion, total count, Coagulase-positive Staphylococci and Clostridium perfringens were 160.000, <100 <10 cfu/g, respectively. Salmonella was not detected in 50 g of the sample, while the total number of yeasts and molds and Sulphite-reducing clostridia were 100 and <10 cfu/g, respectively. After extrusion of broken wheat kernels, total count decreased to 17.000 cfu/g, while the number of Coagulase positive Staphylococci, Clostridium pergringens, Salmonella spp, the total number of yeasts and molds, as well as the number of sulphite-reducing Clostridia was below the limited value. Extrusion process contributes to physico-chemical changes in the material, primarily in the structural change of starch which is reflected in the increase of sucrose and reducing sugar content in the extrudates. Prior to extrusion, wheat broken kernels were grinded in a hammer mill with screen hole of Ø 4mm, then moisture content of ground material was adjusted to 14.80%. Extrusion was performed on single screw extruder "METAL-MATIK" Beočin, at 90°C, capacity 150-170 kg/h of grain extrudates. Extrusion head had 8 dies of Ø 10mm. Extruded wheat broken kernels were characterized with moisture, crude ash, crude fiber, crude fat and starch content of 11.81%, 1.68%, 4.43% 1.99% and 69.39%, respectively.