Determinação de atividade de água em ração animal utilizando ressonância magnética nuclear no domínio do tempo

Abstract

Water activity (aw) is one of the key quality parameters in the food and feed industries, as it directly influences microbiological stability, chemical reactions, and product shelf life. Conventional methods for determining aw, although accurate, often require longer analysis times, which motivates the development of rapid and non-destructive techniques. In this context, this study evaluated the application of time-domain nuclear magnetic resonance (TD-NMR) combined with chemometric tools to determine water activity in extruded and pelleted animal feeds. A total of 35 samples under different conditions (ground and non-ground) were analyzed using CPMG and IR pulse sequences to obtain T₂ and T₁ relaxation times. Exploratory PCA revealed clear separation between processing types, reflecting structural differences and variations in water mobility. The Inverse Laplace Transform (ILT) enabled the identification of distinct populations of bound and free water, showing a predominance of strongly bound water in extruded feeds and higher water mobility in pelleted feeds, consistent with experimental aw values. Multiple linear regression (MLR) models were developed to predict aw from relaxation parameters, achieving high performance (R² > 0.99) for class-specific models with low prediction errors. The results demonstrate that the combination of TD-NMR and chemometrics is an efficient, rapid, and non-destructive approach for estimating water activity in animal feeds, contributing to advancements in industrial quality control.