Effect of pH on the physicochemical and binder properties of tigernut starch

Tigernut starch is starch extracted from the tubers of Cyperus esculentus L. a perennial herb commonly known as tigernut. The effect of pH on the foaming, gelatinization, solubility, swelling, paste clarity, viscosity, freeze–thaw stability, and binder efficiency of the starch in buffer solutions of pHs 4, 7, and 9.2, representative of acid, neutral, and alkaline pHs were evaluated. Marked pH responsiveness was observed in all these parameters to varying degrees. The foaming capacity, paste clarity, freeze–thaw stability, swelling, and viscosity increased while only the gelatinization temperature decreased with increasing pH. The pastes obtained at pHs 4 and 7 showed marked instability by forming a mass of hard coarse gel with the first freeze–thaw cycle while the paste of pH 9.2 maintained its normal viscoelastic‐gel texture even after the fourth freeze–thaw cycle. The properties of the ascorbic acid granules and tablets produced by wet granulation, using the pastes as binder showed pH‐responsiveness, with the granule formed with the paste of pH 9.2 showing higher mechanical strength and lower disintegration time. This study thus shows the diversity in the physicochemical and binder properties of tigernut starch with changes in pH.