Environmental response of pectin-stabilized whey protein aggregates

Electrostatically-stabilized complexes are highly sensitive to changes in their local environment. The current study investigated the formation and stability of particles by heating (90 °C, 5 min) whey protein isolate (WPI) and pectin together as affected by the degree of esterification (DE), whey protein (WP):Pectin ratio (8:1, 5:1, and 2:1), and pH (6–4). At pH 6.0, primary complex formation between WP and pectin was shown, whereas this effect was more pronounced for low-methoxyl pectin (LMP) than for high-methoxyl pectin (HMP) based systems. At pH 4.0, maximum opposite net charges on both biopolymers and maximum biopolymer interactions were observed. Heat-treated WP-Pectin mixtures tended to form more compact and stable structures than unheated ones, associated with the lower pH sensitivity of protein. LMP-stabilized WP systems were characterized by many small aggregates (∼15 μm), whereas HMP-stabilized WP systems exhibited large (∼50 μm) but very dense aggregated structures, which is associated with interpolymeric complexation. Since LMP-stabilized WP aggregates meet the size characteristics of milk fat globules, they might have potential to replace parts of fat in fermented milk products.