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 degrees 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 (similar to 15 mu m), whereas HMP-stabilized WP systems exhibited large (similar to 50 mu m) 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. (C) 2013 Elsevier Ltd. All rights reserved.