Variable Temperature Nuclear Magnetic Resonance and Magnetic Resonance Imaging System as a Novel Technique for In Situ Monitoring of Food Phase Transition

A nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system with a 45 mm variable temperature (VT) sample probe (VT-NMR-MRI) was developed as an innovative technique for in situ monitoring of food phase transition. The system was designed to allow for dual deployment in either a freezing (−37 °C) or high temperature (150 °C) environment. The major breakthrough of the developed VT-NMR-MRI system is that it is able to measure the water states simultaneously in situ during food processing. The performance of the VT-NMR-MRI system was evaluated by measuring the phase transition for salmon flesh and hen egg samples. The NMR relaxometry results demonstrated that the freezing point of salmon flesh was −8.08 °C, and the salmon flesh denaturation temperature was 42.16 °C. The protein denaturation of egg was 70.61 °C, and the protein denaturation occurred at 24.12 min. Meanwhile, the use of MRI in phase transition of food was also investigated to gain internal structural information. All these results showed that the VT-NMR-MRI system provided an effective means for in situ monitoring of phase transition in food processing