Abstract:

This study investigated the evolution of the low field nuclear magnetic resonance (LF-NMR) T2 relaxation
characteristics (e.g., relaxation time T21, T22 and T23, corresponding peak area S21, S22, S23 and S22/S23 and the single component
relaxation time T2W) and fatty acid composition (e.g., C14:0, C16:1, C16:0, C18:1, C18:2, and C18:0) of fresh lard adulterated with
increasing proportions of used lard. The correlation model between LF-NMR results and fatty acid composition was
established and verified. The results indicated that with increasing adulteration level, the relaxation time T21 revealed a
significant decrease (P < 0.05), S21 and S22/S23 exhibited linear increases (R2 > 0.9681), and S23, T2W, the content of C18:1 +
C18:2 and the degree of unsaturation (unsaturated to saturated fatty acid ratio) presented a linear reduction. A good binomial
relationship of adulteration ratios with S22 was achieved, yet no obvious relationship with T22 or T23 existed. Regression
analysis showed that the contents of C16:1, C16:0, C18:2, C18:0 and C18:1 + C18:2 and the degree of unsaturation had an excellent
correlation with S21, T21, S22, T23 and T2W. The models could be used to predict the changes of fatty acid composition and the
adulteration ratio of lard sample by LF-NMR characteristics.

Key words: lard, adulteration, fatty acid composition, low field nuclear magnetic resonance (LF-NMR), relaxation characteristics