Studies of the effect of sodium tripolyphosphate on frozen shrimp by physicochemical analytical methods and Low Field Nuclear Magnetic Resonance (LF 1H NMR)

This work describes studies of the sodium tripolyphosphate (Na5P3O10) treatments on frozen shrimp muscle using Low Field Nuclear Magnetic Resonance (LF 1H NMR). Samples containing water only without any additives were used as controls. All experimental data were collected using thawed samples. A close correlation was established between the LF 1H NMR analysis and other physicochemical measurements (p < 0.01) used in this work including moisture, water-holding capacity, pH and color. Bi-exponential fitting of the transverse relaxation (T2) data revealed two water populations in all samples, T21 and T22, corresponding to relaxation times of 21-42 ms and 47-129 ms respectively. The observed differences in the relaxation times were clearly caused by the difference in the level of Na5P3O10. This study demonstrated that LF 1H NMR is a viable technique and can be applied to provide an improved understanding of the effect of additives such as sodium polyphosphate on the quality of frozen shrimps.

► Polyphosphates in shrimp preserve natural moisture leading to higher-quality product. ► LF 1H NMR can be used to investigate changes in water mobility in the food structure. ► The 1H NMR indicated that the additive causes changes in the shrimp muscle structure. ► Correlations were found between the 1H NMR parameters and physicochemical properties. ► 1H NMR is useful for investigating the water distribution in shrimp freezing process.