Abstract:

Low-field nuclear magnetic resonance (LF-NMR) was used to study the change of water content in fresh milk
during the deterioration process. IR pulse sequence and carr-purcell-meiboom-gill (CPMG) pulse sequence were selected to
determine relaxation parameters of fresh milk sample at different storage times. According to the collected relaxation time T1
and T2, the water content of milk samples could be observed. Furthermore, the changing trends of free water and bound water
were concluded by fitting T2 inversion data. This research showed that the total water content of fresh milk decreased firstly
and then increased with the extension of storage time, among which the free water decreased continuously, and the bound
water decreased initially and subsequently increased. The experimental results demonstrated that LF-NMR could be applied
to determine the freshness of milk rapidly and efficiently, which will be beneficial to monitor the quality of fresh milk in real
time during transportation or storage.

Key words: low-field nuclear magnetic resonance (LF-NMR), relaxation time, free water, bound water, rapid detection