Effect of moisture content on extruded dough of green tea breakfast cereal

Abstract

The objective of this research was to investigate the effect of moisture content on properties of green tea breakfast cereal produced from rice bran using extrusion process. The main ingredients contained 93% rice flour, 2% green tea powder, 2% rice bran, 1% salt, 1% sugar and 1% calcium carbonate. The experiment was conducted by varying the initial moisture content (10, 11, 12, 13, 14, and 15% wet basis) of the mixed flour using the completely randomized design. The single screw extruder was operated at 45 rpm feed rate, 200 rpm screw speed and zone 1, 2 and 3 barrel temperatures at 115, 145 and 170°C, respectively. The RVA results showed that increasing moisture content provided the decreasing viscosity of mixed flour but increasing the setback of gels. The consumer acceptance test was examined using 9-point hedonic scaling (n=50). Result showed that consumer preferred the 10% initial moisture content of mixed flour which provided the highest acceptance percentage (83.83%) and the hedonic rating of overall liking, appearance, color, aroma, tea flavor, crispness and stickiness were 5.6±1.4, 5.1±1.4, 5.6±1.5, 5.1±1.8, 5.4±1.7, 6.9±1.4 and 6.5±1.3, respectively. The logistic regression showed that color, aroma, crispness and stickiness influenced the consumer acceptance with odd ratio at 1.32, 1.29, 1.41 and 1.38, respectively. The most acceptable extruded breakfast cereal consisted of 2.96±0.01% moisture content, L*, a* and b* of 64.23±0.81, 0.45±0.81 and 14.16±0.64, respectively, hardness of 5.88±0.09 g.f, expansion ratio of 1.72±0.09, bulk density of 0.17±0.00 g/ml, water solubility index of 97.08±0.02 and water absorption index of 2.31±0.01