Effect of Flour, Gelatin and Salt on Water Status of Tomato Sauce

Tomato pulp was added with flour, gelatin, and salt (and their binary and ternary mixtures), to obtain tomato sauces with different formulations. Water status of the mixes was characterized at different time-space levels by means of water activity, moisture content and 1H rotational and translational molecular mobility (low resolution 1H NMR, 1H D and 1H T2 relaxation times distributions). The effect of different ingredients and water status was very different on macroscopic and molecular indicators. In particular, moisture content decreased with addition of all ingredients, as expected, while water activity was significantly reduced only when salt was added into the formulation by itself or together with flour and/or gelatin. At a molecular level, flour was the most effective ingredient in reducing proton rotational mobility (1H T2 relaxation time), while gelatin further increased proton molecular mobility as compared to the standard. Proton translational mobility was reduced with the addition of all ingredients, more effectively in the presence of gelatin and flour. It is interesting to point out the different molecular dynamics developed by these two thickening agents although their similar macroscopic effect in tomato sauce. Changes in formulation strongly affected water status at all time-space levels investigated in a complex manner, and the effect of each single ingredient should be carefully considered in the production of tomato sauces as it can affect product properties and stability.