2.3.3. Nuclear Magnetic Resonance Spectroscopy (NMR)
All tests were performed with a flat-bottom glass NMR tube (10 mm diameter, 180 mm length) and each formulation was tested in triplicate. Each tube was filled with bigel sample to a height of 2-in and were covered with parafilm to prevent moisture loss. Proton relaxation measurements were performed on a Bruker minispec mq-20 low-resolution spectrometer (Bruker, Biospin Corporation, Billerica, MA, USA) at a resonance frequency of 20 MHz. Before measurement, the samples were held at 22℃ in a high precision dry bath system for 30 min. The NMR instrument was connected to a water bath circulator to keep the probe head at a constant temperature of 22℃ and ensure temperature did not contribute to differences in proton relaxation.
The Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence was used to measure T2 between 0.2 and 2000 ms. Separation between the 90° and 180° pulses was 2.28 and 4.98 ls, respectively, and 500 data points were collected. For CPMG measurements, 8 scans were made with a 15.0-s recycle delay. Gain was adjusted for each sample to ensure the highest signal was close to 80%. Relaxation curves were fitted to a continuous distribution of exponentials using the Inverse Laplace Transformation (ILT) algorithm, also referred as the CONTIN algorithm of Provencher (1982). Solid fat content (SFC) was also measured in all samples.