Effect of feed mixture and extrusion temperature on physicochemical and sensory properties of barley flour- carrot pomace snack

Snack foods have become an important part of the people’s diets. During last decade demands for utilization of fruit and vegetable waste in order to their dietary fibers in value added food products has been increased. Carrot pomace is rich in dietary fiber that contains important functional and nutritional properties. Barley contains a high amount of dietary fiber, especially soluble fiber, which has essential role in reducing blood cholesterol level. In this project based on Central Composite Design, the effect of independent variables containing extrusion temperature (120-170 °C), moisture content (14-20%) and carrot pomace level (10-25%) were evaluated on expansion ratio, bulk density, WAI, WSI, hardness, color snacks were evaluated by panelists in terms of acceptance or non-acceptance. Results expressed that expansion ratio, lightness, total acceptability and WAI decreased by increasing the amount of carrot pomace. Reduction of expansion ratio and WSI and improvement of lightness and WAI were shown as increased in moisture levels. The hardness and bulk density decreased with an increase in temperature. When temperature increased up to 145°C, expansion ratio, lightness, WAI and WSI increased and decreased thereafter. The optimum conditions for barley flour-carrot pomace snack were determined at the maximum expansion ratio, L*, WAI and overall acceptability with minimum bulk density and hardness in a snack. The optimum condition provides the highest value of expansion ratio 296.1 (%), L* 65.087, WAI 4.931 (g/g) and overall acceptability 4.502 with lowest bulk density 1.22 (g/cm3) and hardness 6.756 (N). Accordingly, the optimum conditions for the snack are 10% carrot pomace, 148°C die temperature and 15.49% moisture. The approximate composition of the snack extruded and unextruded obtained under the optimal conditions. Extrusion did not affect the protein and ash contents but it decreased the fat content of snack. During the extrusion, the SDF increased from 7.63 to 9.27 g/100g while the IDF decreased from 5.24 to 3.71 g/100g. Extrusion cooking did not affect the TBG content in barley flour-carrot pomace snack. Extrusion cooking resulted in the conversion of insoluble to soluble fiber and well balance of both types of the fiber