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.