<Emphasis Type="Italic">In situ</Emphasis> monitoring of solid fat content by means of pulsed nuclear magnetic resonance spectrometry and ultrasonics

An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC. TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r ²>0.9) in a linear fashion (v=2.601 SFC+1433.0).     

New technologies to determine solid fat content on-line

The determination of solid fat content (SFC) is an important analytical procedure in the food industry. The most common way to determine SFC is by low-resolution pulsed NMR (p-NMR). Although this technique is very sensitive and easy to use, it has the disadvantage that it cannot be used for on-line measurements. The present work compares new technologies to determine SFC on-line. On-line ultrasonic spectroscopy and NMR-MOUSE (NMR mobile universal surface explorer) techniques were compared with off-line p-NMR measurements and there was a good correlation between the values obtained. Ultrasonic measurements accurately described the SFC variation, whereas NMR-MOUSE determinations need to be improved to some extent owing to a strong temperature and motion dependence. These two techniques can be used as on-line methodologies to determine SFC during the crystallization of fats.