Effects of corn steep water pretreatment on the rheological and microstructural properties of Ga-kenkey

Abstract

The rheological and textural characteristics of Ga-kenkey are critical for consumer acceptability of the product. This work studied the effects of corn steep water pretreatment with potassium metabisulfite on the rheological properties of Ga-kenkey. The pasting properties of corn dough obtained from corn that was soaked in water treated with and without potassium metabisulfite were determined using the Brabender viscoamylograph. The viscoelastic properties of Ga-kenkey obtained from the sulfited and nonsulfited steeped corn were determined using the TAXT2i Texture Analyzer. There was no detectable residual sulfur dioxide in Ga-kenkey obtained from metabisulfite treated corn. Metabisulfite treatment of steep water did not significantly change the pasting temperature of corn dough (80.15–80.40 °C). However, viscosities of the pastes increased tremendously for dough obtained from corn that was steeped in metabisulfite treated water. In particular, while viscosity at 50-Hold for dough obtained from metabisulfite treated corn was 191BU, it was 140BU for dough obtained from nonmetabisulfite treated corn. The stress relaxation parameters indicated that Ga-kenkey obtained from corn that was steeped in metabisulfite treated water exhibited more pronounced elastic behavior (equilibrium modulus, Ee = 0.695 kPa) and were stiffer than that obtained from corn that was steeped in water without metabisulfite treatment (equilibrium modulus, Ee = 0.399 kPa). SEM showed that Ga-kenkey obtained from both soaking treatments had some amounts of native starch, but Ga-kenkey obtained from sulfited steep water showed a more compact microstructure with more extensive starch transformations than that obtained from nonsulfited steep water. Practical applications Kenkey is a staple food in Ghana, and its processing and sale provide employment to many people. The operations in this cottage industry need to be standardized and eventually industrialized. Consequently, the effects of key unit operations on product quality characteristics need to be rationalized and improved. In the traditional kenkey process, the corn steep water is typically discarded without further treatment. However, disposing large quantities of corn steep water without pretreatment will eventually raise environmental problems because of the foul smell. Steeping corn in dilute potassium metabisulfite will retard the growth of putrefactive organisms and prevent foul odor development in the steep water, but may affect the textural characteristics of Ga-Kenkey.