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

Endogenous alpha-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 (dH(2)O) control are compared for their ability to inhibit alpha-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 alpha-amylase in the flour of rice cultivar Doongara during gelatinization is 1% (w/v) (approximate to 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 dH(2)O control, while breakdown and pasting temperature are significantly lower. In conclusion, the incorporation of 1% (w/v) AgNO3 into samples for RVA inhibits the alpha-amylase activity in rice flour with medium to high AC, allowing pasting properties to be accurately measured using an RVA.

Automated summary

In rice flour with medium to high amylose content, the optimal concentration of silver nitrate to inhibit alpha-amylase during gelatinization is 1% (w/v). Incorporating this concentration into samples allows for accurate measurement of pasting properties using an RVA, with peak viscosity increasing significantly while breakdown and pasting temperature decreasing.