Impact of alfalfa (Medicago sativa L.) galactomannan on the microstructural and physicochemical changes of milk proteins under static in-vitro digestion conditions

This paper reports on the impact of alfalfa galactomannan (AAG, 0.1, 0.5 or 1% wt.) on the colloidal changes and digestibility of sodium caseinate (NaCN) and whey protein isolate (WPI) dispersions (10% wt.) under static in-vitro digestion conditions. Static laser light scattering and confocal laser scanning microscopy-assisted assessment of the NaCN-based gastric chymes confirmed the ability of AAG to control the acid-induced protein coagulation phenomena. Contrarily, the presence of AAG in the WPI-based gastric chymes was associated with the formation of larger aggregates due to the occurrence of segregative microphase separation. The kinetic modelling of the SDS-PAGE densitometric data showed that the intragastric peptic cleavage rates were higher for caseins than whey proteins (β-lactoglobulin, α-lactalbumin). However, free amino acid (FAA) release rates did not exceed 12% under intragastric conditions, whilst notably higher release rates were achieved in the intestinal digesta (36–52%). In all cases, the FAA release rates significantly increased in the presence of AAG.