Lentil flours with different degrees of cellular intactness as thickening agents in high-moisture viscous foods: A case study on tomato soup

In this study, the thickening potential of red lentil flours with different degrees of cellular intactness was evaluated in water (10.7% w/w ) and in tomato soup. Flours with different microstructures were created by blending open-cell (originating from raw-milled lentils) and cellular (originating from lentils milled after hydrothermal treatment) flour together in different ratios. The viscosity and yield stress of flour-in-water dispersions followed power models as a function of the fraction of open-cell flour in the blend, indicating a strong decrease in thickening potential of the flour upon incorporation of intact cotyledon cells. Consistency measurements (IDDSI syringe flow test and Bostwick consistometry) and rheological properties (viscosity and yield stress) were examined for tomato soups thickened with different concentrations of 100%, 80% and 60% open-cell lentil flour blends and compared to a conventionally used thickener, namely modified maize starch. The IDDSI syringe flow test result related linearly to the concentration of thickener, while all other properties showed a power model behavior. Modified maize starch showed the strongest thickening potential, followed by 100% open-cell flour, as the concentration of free starch showed to be the predominant factor determining the thickening potential of lentil flour in tomato soup. Finally, strong relations were observed between consistency and rheological properties of thickened tomato soups. It was shown that the rheological properties of tomato soups thickened with lentil flours can be predicted by consistency measurements, independent of lentil flour microstructure.