Elaboration and Characterization of Whey Protein Beads by an Emulsification/Cold Gelation Process:  Application for the Protection of Retinol

Abstract

Whey protein beads were successfully produced using a new emulsification/cold gelation method. The principle of this method is based on an emulsifying step followed by a Ca(2+)-induced gelation of pre-denatured (80 degreesC/30 min) whey protein. Beads are formed by the dropwise addition of the suspension into a calcium chloride (CaCl(2)) solution. IR results show that bead formation has a pronounced effect on the secondary structure of whey protein, which leads to the formation of intermolecular hydrogen-bonded beta-sheet structures. Their preparation conditions (CaCl(2) concentrations of 10, 15, and 20% (w/w)) influence their sphericity and homogeneity: an increase in CaCl(2) favors regular-shaped beads. The physicochemical and mechanical characterizations of beads were also carried out. Their properties, such as swelling, elasticity, deformability, and resistance at fracture, change according to pH levels (1.9, 4.5, and 7.5) and preparation conditions. Indeed, protein chain networks exhibit different behavior patterns with respect to their charge. Finally, bead degradation by enzymatic hydrolysis reveals that beads are gastroresistant and form good matrixes to protect fat-soluble bioactive molecules such as retinol, that have in vivo intestinal absorption sites. The experiment demonstrated the potential of whey protein beads to protect molecules sensitive (i.e., vitamins) to oxidation.

Cold-set whey protein microgels containing immobilised lipid phases to modulate matrix digestion and release of a water-soluble bioactive

“…The effect of the lipid load within the matrix in delaying enzymatic digestion, and in particular impeding pepsin digestion is consistent with results reported by Beaulieu et al (2002). Indeed, reports (Beaulieu et al, 2002) suggest that hydrophobic amino acid residues left exposed during the denaturation step interact with the lipid phase in the final microgels, thereby masking them against enzymatic digestion.…”

“…In the internal gelation method an insoluble calcium source is mixed into the denatured WPI, and these pre-gel droplets dispersed within an oil phase are gelled upon the addition of an oil soluble acid, which releases the calcium to initiate gelling from within the droplets. These WP microgels are very efficient immobilisers of lipid phases as previously reported by Egan et al (2013), and by Beaulieu et al (2002) for the external gelation method.…”

“…Indeed, reports (Beaulieu et al, 2002) suggest that hydrophobic amino acid residues left exposed during the denaturation step interact with the lipid phase in the final microgels, thereby masking them against enzymatic digestion. It has also been suggested that the products of partial protein hydrolysis can again adsorb to the oil droplet surface and have an additional protective effect on impeding digestion of the matrices (Liang et al, 2010).…”

“…Hydrophobic residues of WPs, adsorbed at the interface of the oil droplets successfully bring those oil droplets into the network of the gel matrix, giving rise to 3D junctions interconnecting the protein and lipid, which can provide a physical restraint against gel swelling (Jost et al, 1986;Mor et al, 1999;Leung Sok Line et al, 2005). Additionally, Beaulieu et al (2002) reported on the preparation of gastric resistant WP microgels containing a lipophilic bioactive by an extrusion based method. The researchers related this effect to pepsin-susceptible hydrophobic aromatic amino acids being masked from enzyme attack, because those groups were either interacting with the lipid phase or efficiently entrapped within the matrix after cross-linking with calcium.…”

Optimization of dynamic loop mixer operating conditions for production of O/W emulsion for cell microencapsulation

“…Cold-set gelation is generally achieved by adding Ca 2+ ions to a WPI suspension preheated under specific conditions [3,15]. The production of water-insoluble wheyprotein beads using an emulsification/cold gelation process has recently been proposed for protection and subsequent release in the intestine of bioactive molecules sensitive to the gastric environment [4]. The gastroresistance properties of cold-set gel of whey proteins along with their aforementioned microencapsulating properties may offer unique opportunities for developing capsules with controlled release in the intestine of active food or nutraceutical ingredients, such as probiotic organisms.…”