Temperature Measurement of Foods Using Chemical Shift Magnetic Resonance Imaging as Compared with T1‐weighted Temperature Mapping

Abstract

A method based on change in proton precession frequency with temperature was compared with temperature measurement by T1-weighted imaging. Temperature maps of a gel, and of cooked and raw red potatoes were developed during heating from 20 to 60ЊC. To measure change in proton precession frequency, a steady state free precession sequence allowed 2-dimensional acquisitions in 8 sec with spatial resolution of 0.88 mm 2 . Temperature resolution with chemical shift imaging, ranged from 0.3 to 3ЊC, decreasing with increasing temperature due to a decrease in signal to noise ratio. The difference by this method and thermocouples was Ͻ 5ЊC. T1-weighted spin-echo images showed artifacts due to an inhomogeneous T1 distribution within the potatoes, indicating chemical shift was more reliable for inhomogeneous foods.

Three‐dimensional MRI mapping of minimum temperatures achieved in microwave and conventional food processing

“…From the initial calibration work that established which MRI parameter was most suited for temperature mapping, a temperature resolution of 1 °C per cm 3 was found to be achievable. Similar results have been found for a variety of food‐related materials (Kantt et al ., 1997). However, the temperature resolution is ultimately dependent on the properties of the sample (T1, T2 and the proton density) and the experimental parameters (TR, Ny, NA, Nz etc.)…”

“…As the experiment was not designed to avoid temperature gradients in the vertical direction, it is expected that there will be some numerical differences in temperature values at corresponding points on the MR and thermal images; therefore, a quantitative comparison of the two sets of images is not presented. This should not be confused with calibration of the MR technique, which has been shown to be accurate to < 1 °C for homogeneous systems and < 5 °C for heterogeneous systems with current protocols (Kantt et al ., 1997).…”

“…In contrast, phase mapping, which uses the sensitivity of chemical shift to temperature, is less dependent on the structural‐ and, to a certain extent, compositional heterogeneity in water‐based foodstuffs. Studies on a variety of food‐related materials gave temperature sensitivities similar to that of pure water (Ishihara et al ., 1995; Kantt et al ., 1997). Kantt et al .…”

Design of Conservative Simulated Particles for Validation of a Multiphase Aseptic Process

“…In a recent research study, a method of generating residence time measurements for particulate foods using magnetic implants and sensors was developed (Swartzel and Simunovic 2003, 2004). Several methods have been proposed for real‐time–temperature measurements in food particulates for validation, such as using small paramagnetic particles in the interior of simulated and real food particles (Ghiron and Litchfield 1997; Ghiron and Litchfield 1998), in‐process measurement of internal particulate temperature utilizing ultrasonic tomography (Beller 1993), a method based on change in proton precession frequency with temperature (Kantt and others 1997), magnetic resonance imaging (MRI) (Kantt and others 1998) and microthermometry (Reiffel 2001; Higgins 2004). Saksena (2001) developed a noncontact system and method for effectively approximating the internal temperature of a food being cooked on a hot surface.…”

Temperature Mapping of Particles During Aseptic Processing with Magnetic Resonance Imaging

“…The change in the resonant frequency of protons with temperature (known as chemical shift imaging or phase mapping) has been proposed as an alternative MRI method for temperature measurement (De Poorter et al, 1994Ishihara et al, 1995;Kantt et al, 1996).…”