Rapid Method for Determining Viscosity Breakdown of Wheat Flour Using Rapid Visco-Analyzer

Studies on Physicochemical Properties of Sprouted Wheat Part II

Abstract

To establish a rapid method for estimating maximum viscosity and breakdown of viscogram, effectiveness of Rapid Visco-Analyzer (RVA) was examined in the presence of ethylene diamine tetraacetic acid (EDTA (2K)) as an inhibitor of α-amylase. The results are as follows; 1. Viscosity parameters equivalent to maximum and minimum viscosity and breakdown of viscogram were measured by RVA under the following conditions for each measurement: (1) Amount of samples of whole meal: 4.3g, (2) EDTA solution: 25ml of 0.1M EDTA (2K), (3) Temperature and duration of measurement: 93°C for 12 to 13 minutes, (4) Items to be measured: maximum viscosity, minimum viscosity which was measured at 10min after the maximum viscosity was observed, and breakdown which was calculated from maximum viscosity minus minimum viscosity. This method gave good reproducibility as errors did not exceed about ±10 points from the average and its coefficient of variance was in an order of 1%. 2. Breakdown of viscogram began to reduce rapidly around 300 BU. When the slurry was prepared with 0.1M EDTA (2K) solution, breakdown of sprouted wheat flour was observed to be the same as the sound one. 3. A high correlation, r=0.649^* (n=13), was observed between RVA breakdown of whole meal and viscogram breakdown of wheat flour, and a higher one, r=0.908^*** (n=29), was observed in case of rice powder. The results showed that this method can be used practically for rapid estimation of breakdown of viscosity. 4. RVA had lower sensitivity to maximum viscosity and breakdown than viscograph in terms of range measured by the difference between the largest and the smallest values. The sensitivity was improved and the correlation was increased by holding the slurry at 60°C for two minutes for maximum viscosity and by gelatinizing at 90°C instead of 93°C for breakdown. (Ex. Correlation coefficient of wheat flour described above was improved from r=0.649^* to r=0.746**)