A DIFFERENTIAL SCANNING CALORIMETRY STUDY OF WHEAT-GRAIN COOKING

A number of commercial processes involve whole grain cooking. In this study, differential scanning calorimetry (DSC) scans were taken of who le wheat grains that had been boiled or steamed for various times at e ither 100 degrees C or 120 degrees C. Scans were also taken of raw gra ins that had been soaked and equilibrated to different moisture conten ts. Raw grains showed peak temperatures to be dependent on moisture co ntent, in close agreement with literature data for wheat starch/water mixtures. The two cooking methods showed different behaviour, which ca n be explained with reference to magnetic resonance imaging (MRI) (Sta pley et al., 1997). For steamed grains with high moisture contents at longer cooking times, part of the DSC endotherm was below the cooking temperature, and conversion occurred in the cooker. DSC endotherms of steamed grains showed a clearly defined onset temperature, c. 6 degree s C, above the steam temperature, due to the release of latent heat. M RI shows partially boiled grains to have a high moisture content in th e outer regions and an inner core of lower moisture content. The peak temperatures observed by DSC were similar to those expected of soaked grains with the same moisture contents as that of the core. It is post ulated that the inner core contains unconverted starch, and that conve rsion has been achieved in the outer regions. The specific heat capaci ty for each grain was also measured, and correlated well with moisture content, but was not strongly influenced by the grain treatment.