Effect of storage temperature on falling number and apparent viscosity of gruels from wheat flours

The study was aimed at the determination of the effect of storage time and temperature on the falling number and apparent viscosity of gruels from wheat flours. Flours of spring and winter wheat were kept in storage for adopted periods of time (2, 4 and 6 weeks) in tightly closed containers at temperatures of 20 °C, 4 °C and −20 °C. Measurements of apparent viscosity of gruels were made using a rotary viscometer. An effect of storage temperature of wheat flours on the direction of changes in the falling number was shown; an increase was observed in falling number values for flours stored at 20 °C, and a decrease of falling number for flours stored at −20 °C. Measurements of viscosity revealed, e.g. an increase of initial and maximum viscosity of wheat flours after the 6-week period of storage, as compared to the viscosity of gruels measured immediately after grinding, though also in this case the differences were not large. Statistical analysis of the results obtained demonstrated a significant linear correlation between the falling number and the apparent viscosity of gruels of the flours, measured at 95 °C, after 15 min. at temp. of 95 °C, and the final viscosity, through the whole period of storage of the flours, irrespective of the storage temperature applied. The results obtained from the measurements of viscosity of gruels wheat flours can be used for the estimation of the values of falling number.