Monitoring fat crystallization in aerated food emulsions by combined DSC and time-resolved synchrotron X-ray diffraction

The thermal and structural evolutions associated to the fat crystallization in a whipped emulsion made from interesterified palm oil are monitored using a new instrument allowing simultaneous time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT). This is performed simultaneously with high sensitivity differential scanning calorimetry (DSC) that is carried out in the same apparatus at scanning rates between 0. 0 1 and 10 K/min on the same sample (typical: 20 mg) in the -30 to + 230 degreesC range. The thermal and structural properties of palm oil-based emulsions are also studied. It is found that the combination of these techniques allows the thermal monitoring of fat polymorphism even within the fat droplets at scanning rates of up to 5 K/min. The formation of alpha, beta' and beta phases,and their transitions are followed simultaneously by DSC and XRDT allowing the identification of the thermal events recorded. It is shown that this interpretation is only possible when high resolution X-ray scattering at small angles and wide angles is coupled with DSC from the same sample. (C) 2002 Elsevier Science Ltd. All rights reserved.