Exploring the breakdown of dairy protein gels during in vitro gastric digestion using time-lapse synchrotron deep-UV fluorescence microscopy
Résumé
A novel time-lapse synchrotron deep-UV microscopy methodology was developed that made use of the
natural tryptophan fluorescence of proteins. It enabled the monitoring in situ of the microstructural
changes of protein gels during simulated gastric digestion. Two dairy gels with an identical composition,
but differing by the coagulation mode, were submitted to static in vitro gastric digestion. The kinetics of
gel particle breakdown were quantified by image analysis and physico-chemical analyses of digesta. The
results confirm the tendency of rennet gels, but not acid gels, to form compact protein aggregates under
acidic conditions of the stomach. Consequently, the kinetics of proteolysis were much slower for the rennet
gel, confirming the hypothesis of a reduced pepsin accessibility to its substrate. The particle shapes
remained unchanged and the disintegration kinetics followed an exponential trend, suggesting that erosion
was the predominant mechanism of the enzymatic breakdown of dairy gels in these experimental
conditions.
