EFFECT OF WET-MILLING PROCESS ON DAMAGED STARCH CONTENT AND GELATINIZATION PROPERTIES OF GLUTINOUS RICE FLOUR

Damaged starch will be produced unavoidably in the milling process of glutinous rice,which will affect the processing quality of glutinous rice flour.In order to meet the needs of processing technology of glutinous rice flour,the effect of soaking time,soak solution,soak temperature,grinding times and drying temperature on the damaged starch content and pasting properties of glutinous rice flour prepared by wet-milling processing was investigated in the present study.The correlation in the wet milling process,damaged starch and the gelatinization characteristics were also analyzed.The results showed that:when the glutinous rice flour was soaked for 60 min,the content of damaged starch decreased to 6.13%,which was decreased to 5.29% with the immersion temperature (less than 45℃) of 30℃.Citric acid and sodium hydroxide solution did not improve the characteristics of glutinous rice flour,while tap water could be used as the soaking solution.With the increasing of the grinding times,the particle size of glutinous rice flour particle size became smaller and the quality was improved,but the improvement of the quality was not obvious and the damaged starch content increased after grinding for 2 times.Drying temperature had a great effect on gelatinization of glutinous rice flour.When drying temperature was 50℃ and 60℃,the content of damaged starch was significantly higher than that of other drying temperature.The effect of different milling conditions on gelatinization properties had significant difference.Correlations analysis showed that significant correlation existed in milling conditions,damaged starch and gelatinization properties.The results showed that the soaking time was significantly correlated with the peak viscosity,the trough viscosity,the decay value,the final viscosity and the regenerated value (r=0.660;r=0.587;r=0.650;r=0.564;r=-0.587).The soaking solution had a significant correlation with the viscosity,the final viscosity,the peak time and gelatinization temperature (r=0.418;r=0.446;r=0.615;r=0.683).And the grinding times also had a significant correlation with the damaged starch content (r=0.646).It was concluded that the better quality of glutinous rice flour was afforded with the conditions of water soaking for 120 min at 40~45℃,grinding for 1~2 times and drying at 40℃ or 80℃.