Comparison of methods for postprandial intragastric pH measurement in a pig model during digestion of plant-based foods with different structures
Résumé
Introduction
Luminal pH is a key determinant of food disintegration in the stomach, acting both on their biochemical
structures and on the activity of digestive enzymes.
Objective
The present study aimed at monitoring postprandial intragastric pH variation after ingestion of four
plant-based meals having the same macronutrients content: two liquids (soymilk and a pea emulsion)
and two solids (seitan and tofu).
Methodology
Four mini-pigs fitted with a gastric cannula located on the stomach greater curve were used. Three
recording methods were compared: chyme sampling from cannula, a classic pH meter-catheter
equipped with two probes or a wireless pH sensor directly put inside the stomach through the canula.
Gastric emptying was also investigated using indigestible markers sampled from duodenal cannula
on six other mini-pigs. In vitro multi-scale characterization in gastric condition were assessed in
in vitro conditions in order to explain intragastric pH differences observed in vivo.
Main findings
Distribution of variation coefficients allowed us to detect the method inducing the less interindividual
variability. The average values obtained from the catheter system and the wireless sensor were
consistent with each other, while sampling method gave less meaningful results. Food effect was
highlighted: an exponential decrease occurred with solids while liquids observed a plateau at pH 7
that lasted about 2h before a sigmoid-type decrease. The seitan appeared to empty faster from the
stomach than the other foods, that could explain the quick pH decrease observed in the stomach. It
was not the case for tofu explained probably by aggregation, buffering capacity or nitrogen solubility.
Finally, entire gastric pH curves were modeled for each meal, that will be useful for implementing in
vitro dynamic digestion in relevant conditions.
Conclusion
In conclusion, pH recording with catheter remained better than other methods and food macrostructure
appeared to impact significantly gastric pH.