A comparative study of the gelation properties of whey protein concentrate and whey protein isolate

Abstract

-The present paper describes a comparative study of the gelation properties of whey protein concentrate (WPC) and whey protein isolate (WPI). Penetration measurements as well as rheological studies revealed that the strength of heat-induced gels prepared with WPI was higher than with WPC. In addition, gels with WPI were clearly more elastic than WPC gels. The storage modulus of WPI and the storage and loss moduli of WPC increased with increasing frequency, while the loss modulus of WPI revealed no clear dependence on the frequency, resulting in a greater decrease in the loss angle of WPI with increasing frequency. The superior gelation properties of WPI were mainly due to the higher β-lactoglobulin content as well as to lower fat, lactose and phospholipid contents. However, in this paper it is also discussed whether the low contents of glycomacropeptide, non-protein-nitrogen and proteose peptone in WPI may partly explain the superior gelation properties of these protein products. WPI were more sensible to an increase in the ionic strength (0.1-0.3% NaCl) than WPC, resulting in clearly stronger gels with WPI than with WPC. In the pH ranges of 2-3 and 7-8, elastic and translucent gels could be prepared using WPI, while their gel-forming properties were low between pH 4 and 5. The strongest gels, turbid, but still elastic, were prepared with WPI at pH 6. whey protein concentrate / whey protein isolate / gelation properties Résumé -Présentation d'une étude comparative sur les propriétés de gélification du concentré protéique de lactosérum WPC et de l'isolat protéique de lactosérum WPI. Des mesures de la pénétration ainsi que des études rhéologiques révèlent que la solidité des gels obtenus par gélifi-cation thermique est plus élevée en utilisant WPI que WPC. De plus, les gels avec WPI sont nettement plus élastiques que des gels avec WPC. Le module de stockage de WPI et les modules de stockage et de perte de WPC augmentaient avec une fréquence croissante, tandis que les modules de perte de WPI n'étaient pas influencés par la fréquence, et menaient ainsi à une forte réduction de l'angle de perte de WPI avec une fréquence croissante. Les propriétés supérieures de gélification de WPI sont principalement dues à une teneur élevée en β-lactoglobuline et à une teneur réduite en matière grasse, lactose et phospholipide. Dans l'étude présente, il est également discuté si les faibles teneurs en glycomacropeptide, en azote non-protéique de WPI et en protéose peptone dans WPI expliquent partiellement les propriétés supérieures de gélification de ces produits protéiques. WPI réagissait plus sensiblement à une augmentation de la teneur ionique (0.1-0.3% NaCl) que WPC, aboutissant à des gels ostensiblement plus solides avec WPI qu'avec WPC. Avec un pH entre 2-3 et 7-8, il a été possible de préparer des gels élastiques et translucides en utilisant WPI, tandis que les propriétés gélifiantes étaient faibles avec un pH entre 4-5. Les gels les plus solides, d'un aspect trouble mais encore élastiques, étaient préparés avec WPI à...

Liquid Whey Protein Concentrates Produced by Ultrafiltration as Primary Raw Materials for Thermal Dairy Gels

“…An exception was found in the case of the defatted gel at pH=4, with a significant decrease in the elastic and viscous modulus (Table 3) when the protein mass fraction was increased. The results for G' and G'' are in the same range of magnitude of the values found in other works for gels produced with bovine WPC (39)(40)(41). However, they are lower than the values found for caprine WPC (39,42) or ovine WPC (39,43) gels.…”

Effect of whey protein purity and glycerol content upon physical properties of edible films manufactured therefrom

“…WPI films showed lower DE values than WPC ones, and these differences were significant (p < 0.05). In addition, WPC films exhibited higher values of b than WPI ones (data not shown); this fact was consistent with the slightly yellowish color observed in WPC films, which may be attributed to presence of contaminants e especially fat and phospholipids (Lorenzen & Schrader, 2006). For practical uses, however, such a minor defect of WPC films can be overcome via addition of coloring agents, as frequently done in food packaging films, or else by lamination with opaque outer layers (Hong & Krochta, 2006).…”

Protein denaturation and functional properties of Lenient Steam Injection heat treated whey protein concentrate

“…Heat induced aggregation and gelation of WPC is known to be influenced by a variety of factors such as ions, heat treatment and pH (Lorenzen & Schrader, 2006;O'Kennedy & Mounsey, 2009;Schmitt, Bovay, Rouvet, Shojaei-Rami, & Kolodziejczyk, 2007). The most pronounced effect of pH in this study was found when changing from pH 6.0 to pH 6.8 (Fig.…”

“…However, a contribution from alpha-lactalbumin to the network formation has been reported only to take place when B-LG is present (Gezimati, Creamer, & Singh, 1997). The presence of other substances like fat, lactose and phospholipids is also observed to influence the gelation capacity of whey proteins, as whey protein isolate (WPI) makes stronger gels than WPC from a similar source of whey (Lorenzen & Schrader, 2006). The total amount of -SH groups available influences the gelling time as well as the clarity or the opacity of the formed gels in the way that an increased total -SH gives increased opacity and faster gelation (Hillier, Lyster, & Cheeseman, 1980).…”

“…NaCl has been reported able to increase the gel hardness of B-LG gels at pH 8.0 (Mulvihill & Kinsella, 1988) and of ovalbumin gels at neutral pH (Doi, 1993), however, too high salt concentration disrupts the electrostatic interactions leading to a drop in gel strength (Mulvihill & Kinsella, 1988). Differences in conductivity could explain why WPC gelation is negatively affected by NaCl addition, while WPI is positively affected (Lorenzen & Schrader, 2006).…”