Whey protein aggregation under shear conditions – effects of lactose and heating temperature on aggregate size and structure

Abstract

Whey protein concentrates with different lactose contents were heat-and shear-treated in a scraped surface heat exchanger at various temperatures. The properties of the resulting protein aggregates are closely correlated with the denaturation kinetics of ␤-lactoglobulin and the different mechanisms -unfolding and aggregation -which determine the overall reaction rate. At temperatures below 85°C, unfolding is slowed down especially if there is a high content of lactose. A loose, porous aggregate structure is formed and the particle size and the serum binding capacity increase. The smallest aggregates are produced when heating takes place between 85 and 95°C. In the temperature range above 100°C aggregation is the rate-limiting step and the aggregate structure is very dense and compact. The particle size increases and is no longer dependent on the concentration of lactose.

Impact of protein self-assemblages on foam properties

“…Similarly, Spiegel (1999) claimed that in order to form very compact and stable whey protein aggregates with sizes between 0.5 and 10 lm, WPI solutions should be heated at 80-85°C for 1 or 2 min; conversely, higher temperature or longer heat treatment lead to coarse and solid aggregates with diameters around 100 lm, in accordance with our experimental data.…”

Formation of heat-induced protein aggregates in milk as a means to recover the whey protein fraction in cheese manufacture, and potential of heat-treating milk at alkaline pH values in order to keep its rennet coagulation properties. A review

“…by the Centri-Whey process [52,53,161]. The size of the aggregates can be controlled by physical means, including homogenisation [110] or shear of the heated whey [40], or the control of the whey protein denaturation through the temperature of heating [8,147]. At constant temperature, decreasing lactose concentration reduces the protective effect of the sugar on denaturation of the whey proteins [21,124], while a combination of increased heating regimen and lactose concentration produces large aggregates with a sandy texture [70,147].…”

“…The size of the aggregates can be controlled by physical means, including homogenisation [110] or shear of the heated whey [40], or the control of the whey protein denaturation through the temperature of heating [8,147]. At constant temperature, decreasing lactose concentration reduces the protective effect of the sugar on denaturation of the whey proteins [21,124], while a combination of increased heating regimen and lactose concentration produces large aggregates with a sandy texture [70,147]. Adjusting the pH of the whey, generally in the range 3.5 to 7, prior to heat-treatment, is also a common method to control the size and hydration of the aggregates, although the reported optimum pH values differ significantly [40,84,148].…”

The effects of sucrose on the mechanical properties of acid milk proteins-kappa-carrageenan gels

“…This characteristic could be associated with lactose, since such sugar slows down the denaturation of β-lactoglobulin (Spiegel, 1999) and thus weakens the gel network. Another possible explanation for the negative effect of WPC concentration on the mechanical properties of dairy gels could be the strong interaction between caseinate and carrageenan, which could decrease the interaction of these biopolymers with WPC (Tziboula and Horne, 1999) or even exclude it from the elastic network.…”