Claire Mouquet

Viscosity of gruels for infants : a comparison of measurement procedures

Numerous studies have been carried out to investigate energy density and consistency of gruels for infants in developing countries. However, starch-rich gruels have a complex rheological behavior and their consistency is difficult to characterize. Many published gruel viscosity data are available, but the lack of standardized viscosity measurement procedures makes comparisons and interpretations difficult. The influences of viscometer type and viscosity measurement conditions on gruels prepared with simple or multicomponent flours were assessed in this study. The results showed a drastic decrease in apparent viscosity when the shear rate increased. Other factors like shear time and gruel temperature also had a marked influence on apparent viscosity. For two types of gruel (maize or multicomponent flour) prepared at different concentrations, correspondences between a short qualitative description of the consistency and apparent viscosity values obtained with several viscometers in different measurement conditions are given. Finally, recommendations are put forward on techniques to obtain valid data on gruel consistency, adapted to each type of study (laboratory, field or large-scale surveys).

Characterization of the consistency of gruels consumed by infants in developing countries: assessment of the Bostwick consistometer and comparison with viscosity measurements and sensory perception

Standardized techniques are still needed to characterize the consistency of gruels for infants in developing countries. The aim of this study was to evaluate the interest of the use of the Bostwick consistometer. Bostwick flow was measured on gruels prepared with different flours, at low or high energy density (i.e. without or with amylase). The range of Bostwick flow, from 0 to 240 mm/30 sec, adequately described a wide range of gruel consistencies from completely liquid to almost solid. However, the temperature of the gruel must be carefully controlled during measurements as Bostwick flow is highly temperature dependent, especially in the case of gruels with high energy density. The relationship between Bostwick flow and apparent viscosity proved to depend on the type of gruel: at an apparent viscosity of 1 Pa.sec, gruels prepared from maize, rice, millet or multicomponent flours had different Bostwick flow values of, respectively, 20, 35, 75 and 55 mm/30 sec. Sensory analysis was then performed with a panel of mothers of infants and young children in Ouagadougou (Burkina Faso). Gruels of similar apparent viscosity and different Bostwick flow distances or of inversely similar Bostwick flow distances and different apparent viscosities were prepared by adding carob seed flour, and differentiation and ranking tests were then carried out. Both types of test revealed that mothers differentiated similar gruels having different Bostwick flow distances more easily than gruels having different apparent viscosities. It can thus be concluded that Bostwick flow, which is an empirical multi-criteria parameter, conveys the sensory perception of gruel consistency better than apparent viscosity.

Home-processing of the dishes constituting the main sources of micronutrients in the diet of preschool children in rural Burkina Faso

The diet of 200 randomly selected 1-year-old to 5-year-old children was studied in a rural area of Burkina Faso. The mothers took part in a questionnaire survey and a 24-h dietary recall to index the type and the ingested quantities of the food consumed by the child the previous day. The average percentages of the Recommended Nutrient Intake met by the consumption of a dish component per meal did not exceed 25% for energy, iron, zinc and vitamin A. With respect to their initial composition and the quantities ingested, several dish components such as starchy-based products (millet-based-tô) or sauces (red sorrel leaves, dried okra) were good sources of micronutrients in the childrens diets. Several dish components were selected and their preparation observed in six households to obtain precise details of the recipe. Several ingredients (42) and unit operations (nine) were used to prepare the local foods. Cooking in water (boiling), which was the main unit operation, did not exceed 43 min and the temperature used was under 100°C. Several ingredients were subjected to two or three thermal treatments and the duration of cooking reached 56 min in groundnut sauce. The most at-risk unit operations likely to decrease the nutritional quality were cooking in water followed by draining or cooking for a long time.