Optimal Silver Nitrate Concentration to Inhibit α‐Amylase Activity During Pasting of Rice Flour

Abstract

Endogenous α‐amylase interferes with accurate determination of the pasting properties of cereal flour. Silver nitrate (AgNO3) solutions at seven different concentrations (0.001‐0.1 m) plus a deionized water (dH2O) control are compared for their ability to inhibit α‐amylase activity during gelatinization of rice flour with medium to high amylose content (AC). Pasting properties are assessed using a Rapid Visco Analyzer (RVA). The optimal concentration of AgNO3 to inhibit α‐amylase in the flour of rice cultivar Doongara during gelatinization is 1% (w/v) (≈0.06 m). This concentration is tested further in three other types of rice for confirmation of the effects on RVA pasting properties. Peak viscosity is significantly higher using 1% AgNO3 than in the dH2O control, while breakdown and pasting temperature are significantly lower. In conclusion, the incorporation of 1% (w/v) AgNO3 into samples for RVA inhibits the α‐amylase activity in rice flour with medium to high AC, allowing pasting properties to be accurately measured using an RVA.

Characterization of four commercial waxy wheats developed in China

“…From RVA profiles (Figure 1), it was observed that differences (125−170 RVU) in the peak viscosity of the waxy wheat flours between with and without silver nitrate were much higher than that of the normal wheat flour (63 RVU). It is known that silver nitrate inhibits the endogenous α‐amylase (Rahman et al, 2020). These results indicated that the waxy wheat flour was very sensitive to the endogenous α‐amylase even at a very low level of enzyme activity.…”