The effects of konjac flour (KF) for modifying the foaming properties of milk protein concentrate (MPC) and characteristics of gluten-free rice cookies were investigated. The three variables of konjac concentration (0.1–0.4%), pH (pH 5–9) and NaCl concentration (0.2–0.6 m) were studied. Both KF and pH had considerable effects on the foaming capacity (FC) and foaming stability (FS) of MPC. The NaCl had a negligible effect. Lowered FC and FS observed at pH 9 and pH 5 were increased with the increase in KF addition. Batter characteristics (flowability and consistency), cookie quality (moisture, yield, spread ratio, specific volume, hardness and colour) and sensory acceptance were evaluated in gluten-free cookies with 0%, 0.25% and 0.4% KF. Konjac supplementation increased batter characteristics, yield, specific volume and hardness, but decreased lightness. Panellist acceptance, especially regarding texture and overall acceptability, increased in gluten-free cookies with 0.4% KF. A higher purchasing decision was found for cookies with added KF.
Konjac flour has a potential for improving the foam formation and stability of milk protein concentrate. An optimal condition for modified foamability and stability of MPC was found to be 0.4% KF, pH 5.19 and 0.2 m NaCl. Incorporation of 0.25% and 0.4% KF in gluten-free rice cookies improved batter characteristics, physical properties and sensory acceptance.