Kajian pengaruh pengukusan bertekanan (steam pressure treatment) terhadap sifat fisikokimia tepung jagung

Abstract

The objectives of this study were to study the effects of steam pressure treatments on physicochemical properties of corn flour and to apply corn flour for cookies production. The study was conducted in three stages. The first stage was production of corn flour through wet milling process. The second stage was the analysis of physicochemical properties of corn flours that were steam pressure treated for 10, 20, 30, 40, 50 and 60 minutes. The third stage was production of cookies using the pre-treated corn flour. The thermal properties showed that gelatinization transition temperatures (To, Tp, Tc) and gelatinization degrees increased but gelatinization enthalpy and temperature range decreased after steam pressure treatment when processing time increased. The decrease of the gelatinization enthalpy had been related to loss of crystallinity order within the flour granule. The rheological properties showed that maximum viscosity, hot paste viscosity, breakdown viscosity, cold paste viscosity and setback viscosity of pre-treated corn flour decreased after steam pressure treatment when processing time increased. The steam pressure treatment changed the gelatinization profile from B to C type. Correlation analyses showed that the maximum viscosity had positive correlation with swelling volume. The maximum viscosity, hot paste viscosity, breakdown viscosity, cold paste viscosity and setback viscosity had negative correlation with the gelatinization degrees. The swelling volume and water solubility of pre-treated corn flour were significantly affected by the steam pressure time. The swelling volume decreased but the water solubility increased. The steam pressure treatment did not give significant affects to water absorption capacity, amylose content, amilopectin content and moisture content of corn flour. The gelatinization degrees had positive correlation with the water solubility and the water absorption capacity but it had negative correlation with the swelling volume. The water solubility had negative correlation with the gelatinization enthalpy. Application of pre-treated corn flour for cookies production reduced sandiness of cookies. The sandiness of cookies had positive correlation with the gelatinization enthalpy but it had negative correlation with the gelatinization degrees.