Rheological Characterization of Gastric Juices from Bread with Different Amylose/Amylopectin Ratios

The purpose of this paper is to present a methodology for characterizing the rheological properties of heterogeneous gastric contents, for the first time, to our knowledge. Pigs were used as a model because their gastric system is similar to that of humans. Bread was chosen as a high-calorific, solid test meal. The bread was made with flours offering a wide range of amylose/amylopectin ratios. A specific method of extraction and measurement was developed. For the study, the vane test technique was chosen in order to take into account the heterogeneity and short lifetime of the boluses. The variation in viscosity values for each gastric system was compared with their moisture contents, different residence times in the stomach, and various amylose/amylopectin ratios. The viscosities decrease significantly as the residence time increases. Furthermore, we suggest that the amylose/amylopectin ratio (Am/Ap) determines the moisture content, which then provides the viscosity level, since the gastric contents behave as a concentrated suspension. Pigs add variability to the results because the structure of the bolus depends on mastication.