Study On The Preparation Of Cereal Breakfast By Twin-screw Extrusion

The preparation of cereal breakfast by twin-screw extrusion was studied in this paper. Nine kinds of cereals (corn, wheat, rice, oat, barley, millet, black rice, red bean and mung bean) were extruded and the correlation between the composition of cereal materials and physicochemical properties of products were studied. Single factor experiment and orthogonal design were applied for the optimization of the formula of cereal breakfast. The effects of process conditions on system parameters and quality of cereal breakfast were also studied. In addition, the composition and functional properties of the extruded products were analyzed.Firstly, the correlation between the composition of cereal materials and physicochemical properties of products were studied. The results showed that the degree of gelatinization was very significant negative correlation with the protein content (6.86-48.27%) and significant positive correlation with the starch content (42.91-81.36%) of materials, WAI was very significant negative correlation with the protein content and very significant positive correlation with the starch content of materials, WSI was significant positive correlation with the protein content and very significant negative correlation with the starch content and amylose content (6.37-48.27%), and bowl life was significant positive correlation with amylose content. In addition, the result also showed that WSI was significant negative correlation with the degree of gelatinization and very significant negative correlation with WAI, CE was significant negative correlation with LE and significant positive correlation with hardness, crispness was very significant positive correlation with bowl life.Secondly, rice, millet, oat and red bean were selected as raw materials of cereal breakfast. Single factor experiment and orthogonal design combining EAAI, expansion ratio and texture as indicators were applied for the optimization of formula of cereal breakfast. The optimal formula of cereal breakfast is that the content of millet, oat, red bean and rice is 45%, 20%, 20% and 15%, respectively. In this formula, the EAAI is 81.57.Thirdly, the effects of process conditions, such as moisture content, screw temperature and screw speed, on system parameters (die pressure and torque) and quality (expansion ratio, WAI, WSI, texture and colour value) of cereal breakfast, were studied. Die pressure and torque were reduced significantly with the increase of moisture content (22-30%). When screw temperature (120-160℃) was increased, torque was reduced gradually and die pressure was changed irregularly. While increasing the screw speed (80-120 r/min), die pressure was increased and toque was decreased. According to the result of the effects of conditions on the quality of product and the characteristic of cereal breakfast, the optimal process conditions were as follows: moisture content 24%, screw temperature 140℃and screw speed 110 r/min.Lastly, the composition and functional properties were compared between raw materials and cereal breakfast. The content of starch and fat was decreased and reducing sugar was not detected in the product. The content of Ile, Leu, Met and Cys was maintained well. The content of Lys was reduced by 10%, Thr 17.7%, Try 16% and Phe and Tyr 46.6%. The degree of gelatinization of product was 92.17%. WSI was increased to 2.58 times and WAI was doubled.