Physico-chemical, textural and sensory properties of a fried cookie system containing soy protein isolate

A fried cookie, with the local name of Yackwa, was prepared by partially replacing wheatflour with soy protein isolate (SPI). The physico-chemical, textural and sensory characteristics were then investigated. The addition of SPI caused a decrease in fat content and an increase in the moisture and protein content of Yackwa. Dehydration and oil absorption during frying decreased as the level of SPI replacement increased. The dough consistency increased with addition of SPI and was highly correlated with dehydration and oil absorption. Colour determination showed that addition of SPI darkened the external and internal colour of Yackwa, probably because of browning caused by the Maillard reaction. The textural hardness increased with increasing SPI content. The addition of SPI made Yackwa darker, more cracked and liable to fracture, harder and less moist as perceived by sensory panellists. Up to 15% of the wheatflour could be replaced by SPI without diminishing acceptability.