Oil structuring using whey protein-based cryogel particles: Effect of gelation pH and feasibility as an ingredient in low-saturated fat cocoa spreads

Cryogel particles were obtained by freeze-drying and grinding hydrogel monoliths made from 20 % (w/w) whey protein isolate (WP) suspensions prepared at different pH (pH 4.8, 5.7, and 7.0). The microstructure, porosity, and density of the cryogels were strongly affected by the starting pH of the suspension. At pH 4.8, corresponding to the isoelectric point, proteins assumed a globular form leading to a cryogel with the highest porosity and lowest density compared to those formed at higher pH values (5.7 and 7.0). Such morphological differences accounted for different oil structuring capabilities. When mixed with oil, the cryogel particles formed at the pI were capable of entrapping larger quantities of oil (∼63 % w/w) than those obtained distant from the pI (∼47 %, w/w), forming a spreadable material. In this system, as confirmed by confocal microscopy, WP particles were evenly distributed in oil forming a network connected by capillary bridges and surface hydrophilic interactions. Thus, the mixture of sunflower oil with cryogel particles formed at the pI allowed to obtain an oleogel, exploitable for fat replacement, as confirmed by the preparation of a cocoa spread prototype. Results highlighted the critical impact of protein hydrogel structure in determining the ability of the cryogel particles thereof to entrap oil and tune the oleogel characteristics. The potentialities of this innovative material as ingredient of low saturated fat food products were also demonstrated.