Mixtures Of Whey Protein Isolate Research Articles

Peptide–peptide and protein–peptide interactions in mixtures of whey protein isolate and whey protein isolate hydrolysates

Abstract The extent of aggregation in whey protein isolate (WPI) hydrolysates induced by Bacillus licheniformis protease was quantified as a function of degree of hydrolysis (DH), temperature and ionic strength. The capacity of the hydrolysates to aggregate added intact protein was also studied. The amount of aggregated material and the size of the aggregated peptides were measured by nitrogen content and size exclusion chromatography, respectively. Aggregation increased with DH up to the practical end point of hydrolysis (DH 6.8%). The aggregates formed under the various conditions studied consisted of peptides with masses ranging from 1.4 to 7.5 kDa. The hydrolysates were also able to aggregate added WPI. The additional amount of aggregated material increased with increasing DH. Peptides involved in peptide–peptide interactions were also involved in protein–peptide interactions. It is hypothesized that hydrophobic interactions dominated peptide–peptide interactions, while protein–peptide interactions depended on the balance between hydrophobic attraction and electrostatic repulsion.

Gelation properties of soya and whey protein isolate mixtures

Gelation properties of commercially available soya and whey protein isolates (15–18% w/w) were tested in isolation and when mixed in ratios ranging from 17:1 to 1:17 soya/whey to give a final protein concentration of 18% protein (w/w) in distilled water. The isolates and mixtures were investigated by both small and large deformation rheological analysis, which indicated phase separation of the two proteins systems. Phase inversion occurred at 5:1 ratio (soya/whey) where the lowest shear modulus value, by large deformation testing, was 3.5 compared to 5.5 for 18% (w/w) soya and 10.7 for 18% (w/w) whey proteins in distilled water. The G′ value obtained by small deformation testing, also showed the lowest value at the 5:1 ratio (soya/whey proteins). In addition, gels exhibited maximum syneresis at this ratio indicating instability at the point of inversion. Electron microscopy in combination with immunocytochemistry using anti-soya or anti-whey antibodies also indicated phase separation of the two types of proteins. Phase separation was considered to occur due to differences in the molecular sizes of the proteins and physical–chemical differences including hydrophobicity as verified by the cis-parinaric fluorescent probe technique.

Microstructure of Microcapsules Consisting of Whey Proteins and Carbohydrates

ABSTRACTMicrostructure was studied on spray‐dried microcapsules with wall systems consisting of mixtures of whey protein isolate (WPI) and maltodextrins (DE 5, 10, 15) or corn syrup solids (DE 24). Structure of microcapsules was appreciably affected by type of carbohydrate and by the WPI‐to‐carbohydrate ratio. The extent of surface indentation was inversely related to the proportion of WPI in the wall system. Ratio of low‐to‐high molecular weight solutes in the wall system affected structure. At a WPI‐to‐carbohydrate ratio of 1:1 or higher, whey proteins improved the surface‐smoothness and decrease surface indentation of maltodextrin‐based microcapsules. Combinations of WPI with high‐DE value carbohydrates were more effective than those with carbohydrates of low DE value in limiting surface‐dents formation.

Microencapsulation of volatiles by spray-drying in whey protein-based wall systems

Abstract Volatile retention during microencapsulation by spray drying was studied using whey proteins as microencapsulating agents. Ethyl butyrate (EB) and ethyl caprylate (ECY) were microencapsulated in wall systems consisting of whey protein isolate (WPI) or a 1:1 mixture of WPI and lactose (WPI/Lac). Retention of volatiles was significantly affected by wall solids concentration (10–30%, w/w), initial ester load (10–75%, w/w, of wall solids), and by ester and wall type. Ester retention in WPI/Lac was higher than in WPI. Maximum retention levels obtained for (EB) and (ECY) during spray drying were 76 and 92%, respectively, demonstrating the effectiveness of whey protein-based wall systems in microencapsulation of volatiles.

Adsorption behaviour of whey protein isolate and caseinate in soya oil-in-water emulsions

A technique to determine directly the amount of adsorbed protein in protein-stabilized oil-in-water emulsions (20 wt% soya oil, pH 7) has been developed employing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and photometric densitometry. Using this technique the adsorption behaviour of whey protein isolate (WPI) and cascinate at the emulsion droplet surface has been studied. The minimum limiting surface concentrations required to stabilize emulsions containing cascinate or WPI were found to be 1 and 1.5 mg/m 2 respectively. At protein concentrations >2.25 wt% in the aqueous phase, surface concentration of both proteins was at a high limit of ~3.2 mg/m 2. WPI exhibited behaviour indicative of adsorption in distinct multilayers. Competitive adsorption of proteins in emulsions stabilized by mixtures of WPI and cascinate was studied using the same technique, and it was found that when protein concentration was the limiting factor, WPI and cascinate adsorbed to the same extent. However, with an excess of protein, cascinate adsorbed in preference to WPI.