Production of high fiber ready-to-eat expanded snack from barley flour and carrot pomace using extrusion cooking technology

Abstract

The effects of feed moisture content (14, 17 and 20% db), die temperature (120, 145 and 170 °C) and carrot pomace content (10, 17.5 and 25%) on the sectional expansion index, hardness, porosity, micro and macro structure and sensory properties of high fiber expanded barley-carrot pomace snack were investigated using a central composite design. Results showed that with increasing the moisture content the hardness of the extruded snacks increased while their expansion ratio decreased. The hardness decreased with increasing the die temperature, but the expansion ratio increased with increasing the die temperatures to up to 145 °C and decreased afterwards. An increase in carrot pomace content decreased the expansion ratio and cell average size while the hardness and cell wall thickness increased. The optimum condition for production of expanded barley-carrot pomace snack was 10% carrot pomace content, 142.7 °C die temperature and 14.02% moisture content. During extrusion cooking, the soluble dietary fiber of barley-carrot pomace snack increased, but no change on the total dietary fiber content was observed. Therefore, the extruded snacks prepared from barley flour and carrot pomace had high nutritional value.

Keywords: Barley; Carrot pomace; Dietary fiber; Expanded snack; Extrusion cooking.

Fig. 1

Response surface for the effect of carrot pomace content, moisture and temperature on the a expansion ratio and b hardness of snack

Fig. 2

a Correlation between porosity measured by Eq. 2 and porosity calculated by image analysis of the extruded snacks. Response surface for the effect of carrot pomace content, moisture and temperature on the b Porosity measured using Eq. 2 and c porosity from image analysis

Fig. 3

Response surface for the effect of carrot pomace content, moisture and temperature on the cell a average size, b total area, c wall thickness of snack

Fig. 4

Scanning electron micrographs of extruded snack at 110 × (1) and 2000 × (2) magnification. a: 145 °C—10% carrot pomace—17% moisture; b: 145 °C—17.5% carrot pomace—17% moisture; c: 145 °C—25% carrot pomace—17% moisture; d: 120 °C—17.5% carrot pomace—17% moisture; e: 170 °C—17.5% carrot pomace—17% moisture; f: 145 °C—17.5% carrot pomace—14% moisture; g: 145 °C—17.5% carrot pomace—20% moisture

Fig. 5

Response surface for the effect of carrot pomace content, moisture and temperature on the sensory properties snack (a: color, b: crunchiness, c: overall acceptability)