The Effect of Steeping Regimes and Gibberellic Acid (GA3) on Enzymatic Activity of Rice Malt for the Production of Glucose Syrup

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The effect of three malting conditions (steeping period, air-rest, and gibberellic acid-3 application) on malting quality of rice grains for the production of glucose syrup was investigated. The rice grain (Jasmine 85 variety) was soaked for 12 to 72 hours and germinated for 12 days at a temperature of 28 + 1 °C. Air-rest treatment of 2 to 8 hours and GA3 concentrations of 10* to 10 mg/L were applied. Parameters measured included out-of-Steep Moisture Content (SMC), germination energy, malting Joss, diastase and alpha amylase activities, shoot length, protein content, rate of reaction, and total soluble solids (sugars). Results obtained indicated that SMC, malting loss, germination energy, diastatic activity, and shoot length of rice malt increased with increasing steeping period. The effect of air-rest treatment on the rice malt quality was more significant at 6-hour period producing an average diastatic activity of 1001.72 U/g dry malt at out-of-steep and shoot length of 5.24cm. GA3 application at a concentration of lOmg/L resulted in the highest diastatic activity of 1305.27 U/g dry malt, and shoot length of 2.93cm after 60 hours of germination. The maximum diastatic activity of rice malt obtaine4 from the combine (GA3 and air rest) and air-rest treatment alone was found on the 8th day of germination, occurring earlier than that of the control, 10th day. Moreover, the combined treatment produced malt with the highest diastatic activity (1545.94U/g) compared to that of air-rest treatment alone (1528.01U/g) and the control (1456.33U/g), averagely. Cassava starch (Agbelifia) had a higher affinity for the malt prepared under the combined treatment producing more soluble sugars in the final glucose syrup. Therefore to obtain rice malt with the highest diastatic activity, rice grains should be soaked for 48 hours. Moreover, applying air rest-treatment of 6 hours during steeping in lOmg/L of GA3 solution could further enhances the total hydrolytic potential of rice malt.  
A Thesis submitted to the Department of Food Science and Technology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Science, 2009