Viscosity of gruels for infants: a comparison of measurement procedures

Numerous studies have been carried out to investigate energy density and co nsistency of gruels for infants in developing countries. However, starch-ri ch gruels have a complex rheological behavior and their consistency is diff icult to characterize. Many published gruel viscosity data are available, b ut the lack of standardized viscosity measurement procedures makes comparis ons and interpretations difficult. The influences of viscometer type and vi scosity measurement conditions on gruels prepared with simple or multicompo nent flours were assessed in this study. The results showed a drastic decre ase in apparent viscosity when the shear rate increased. Other factors like shear time and gruel temperature also had a marked influence on apparent v iscosity. For two types of gruel (maize or multicomponent flour) prepared a t different concentrations, correspondences between a short qualitative des cription of the consistency and apparent viscosity values obtained with sev eral viscometers in different measurement conditions are given. Finally, re commendations are put forward on techniques to obtain valid data on gruel c onsistency, adapted to each type of study (laboratory, field or large-scale surveys).