Abstract
INTRODUCTION: The addition of starch-based thickening agents to increase the viscosity of infant formula is common practice in primary care. However, this strategy lacks standardized preparation steps and a benchmark for therapeutic effect. Therefore, this study aims: (1) to determine the optimal preparation method for infant formulas (pre-)thickened with starch; (2) to evaluate their viscosity in the bottle; (3) to assess their viscosity under simulated gastric conditions; and (4) to estimate the caloric contribution of externally added starch-based thickeners to standard infant formulas. METHODS: We performed in vitro rheological measurements in a standard formula externally thickened with rice flour [SFRF] and a commercial formula pre-thickened with potato starch [IFPS], using a rotational rheometer under bottle-simulated and gastric-simulated conditions. Experiments were performed across different pH levels (pH 1, pH 4 and pH 7) and at multiple time points (5-60 min). Gastric simulation included the addition of artificial saliva and simulated gastric fluid. A descriptive analysis was performed. RESULTS: The results show that infant formulas containing starch, whether inherently pre-thickened or prepared with added starch-based thickeners, require vigorous shaking to ensure complete solubilization of starch granules. Preparation at 37 °C further supports more proper dispersion over preparation at 20 °C. Standard formulas thickened with rice flour demonstrate limited stability, with a marked decline in viscosity after 20 min at 20 °C, indicating they should be prepared and consumed promptly. In contrast, formulas pre-thickened with potato starch reach their peak viscosity only after approximately 30 min. Nevertheless, when exposed to simulated gastric conditions, the elevated viscosities observed in the bottle for both types are not maintained but rather comparable to those of standard, non-thickened formulas. Furthermore, adding starch-based thickeners substantially elevates the caloric content of infant feeds. CONCLUSION: Our findings suggest that SFRF should be administered within 20 min of preparation and IFPS must be shaken vigorously. The present study highlights potential concerns regarding the in vivo relevance of starch-based thickening for increasing gastric viscosity, although additional studies are warranted to validate these observations.