Foaming and sensory characteristics of protein-polyphenol particles in a food matrix

As food ingredients, protein-polyphenol aggregate particles provide a combination of structural and health-relevant functional benefits. Particles made by complexing whey (WPI) or rice (RPI) protein isolates and blueberry (BB) extracts were evaluated for foaming properties (foam volume, stability, and yield stress) using a high energy-input foaming operation (with an Ultra Power Mixer), and then also compared at low energy-input (foamed using a hand-held mixer). In the high energy-input foaming operation, whey protein rapidly formed foams (within 2 min). Whey protein-blueberry (WPI-BB) particles significantly improved yield stress and foam stability (2-fold) as compared to foams made with unmodified WPI. Rice protein required longer (>8 min) to produce foams, but foams were significantly more stable (longer drainage half-life) both when the protein was unmodified (RPI) or formulated as particles (RPI-BB). Protein-polyphenol particle foams (WPI-BB or RPI-BB) had a much greater proportion of smaller sized bubbles than polyphenol-free foams. WPI foams formed for descriptive analysis using the low energy-input method rapidly produced structures with fine, stable bubbles resistant to breakdown in the mouth, while those made with RPI had fewer, larger and looser bubbles which broke more easily after mixing and in the mouth. Inclusion of WPI-BB or RPI-BB particles enhanced palatability of protein isolates in a model (protein bars) food system as compared to non-complexed proteins. The complexed aggregate particles also provided sweetness, dark berry and dried fruit flavors and minimized bitterness and astringency. This work provides a context for understanding the utilization of protein-polyphenol particles as multifunctional ingredients that simultaneously deliver concentrated polyphenols associated with health benefits.