The anti-inflammatory potential of a moderately hydrolysed casein and its 5 kDa fraction in in vitro and ex vivo models of the gastrointestinal tract.

Bioactive peptides from milk can impart a wide range of physiological benefits without the allergies and intolerance associated with the consumption of whole milk. The objective of this study was to characterise the anti-inflammatory properties of intact sodium caseinate (NaCAS), a moderately hydrolysed NaCAS enzyme hydrolysate (EH) and its 5 kDa fraction (5kDaR), in both in vitro and ex vivo systems. In vitro, Caco-2 cells were stimulated with tumor necrosis factor (TNF) α and co-treated ± casein hydrolysates or dexamethasone (control). The inflammatory marker interleukin (IL)-8 was measured by ELISA in the supernatant at 24 h. Ex vivo, porcine colonic tissues were stimulated with lipopolysaccharide (LPS) and co-treated with casein hydrolysates for 3 h from which the relative expression of a panel of cytokines was measured in vitro. While the steroid dexamethasone brought about a 41.6% reduction in the IL-8 concentration in the supernatant, the 5kDaR reduced IL-8 by 59% (P < 0.05) when compared to the TNFα stimulated Caco-2 cells. In the ex vivo system, 5kDaR was associated with decreases in IL-1α, IL-1ß, IL-8 and TGF-ß expression and an increase in IL-17 expression (P < 0.05) relative to the LPS challenged tissues. We concluded, that a 5 kDa casein fraction demonstrates potent anti-inflammatory effects both in in vitro and ex vivo models of the gastrointestinal tract.

Whey protein isolate polydispersity affects enzymatic hydrolysis outcomes.

The effects of heat-induced denaturation of whey protein isolate (WPI) on the enzymatic breakdown of α-La, caseinomacropeptide (CMP), ß-Lg A and ß-Lg B were observed as hydrolysis proceeded to a 5% degree of hydrolysis (DH) in both unheated and heat-treated (80 °C, 10 min) WPI dispersions (100 g L(-1)). Hydrolysis of denatured WPI favoured the generation of higher levels of free essential amino acids; lysine, phenylalanine and arginine compared to the unheated substrate. LC-MS/MS identified 23 distinct peptides which were identified in the denatured WPI hydrolysate - the majority of which were derived from ß-Lg. The mapping of the detected regions in α-La, ß-Lg, and CMP enabled specific cleavage points to be associated with certain serine endo-protease activities. The outcomes of the study emphasise how a combined approach of substrate heat pre-treatment and enzymology may be used to influence proteolysis with attendant opportunities for targeting unique peptide production and amino acid release.

Enzymatic hydrolysis of heat-induced aggregates of whey protein isolate.

The effects of heat-induced denaturation and subsequent aggregation of whey protein isolate (WPI) solutions on the rate of enzymatic hydrolysis was investigated. Both heated (60 °C, 15 min; 65 °C, 5 and 15 min; 70 °C, 5 and 15 min, 75 °C, 5 and 15 min; 80 °C, 10 min) and unheated WPI solutions (100 g L(-1) protein) were incubated with a commercial proteolytic enzyme preparation, Corolase PP, until they reached a target degree of hydrolysis (DH) of 5%. WPI solutions on heating were characterized by large aggregate formation, higher viscosity, and surface hydrophobicity and hydrolyzed more rapidly (P < 0.001) than the unheated. The whey proteins exhibited differences in their susceptibility to hydrolysis. Both viscosity and surface hydrophobicity along with insolubility declined as hydrolysis progressed. However, microstructural changes observed by light and confocal laser scanning microscopy (CLSM) provided insights to suggest that aggregate size and porosity may be complementary to denaturation in promoting faster enzymatic hydrolysis. This could be clearly observed in the course of aggregate disintegration, gel network breakdown, and improved solution clarification.