Whey protein-polyphenol aggregate particles mitigate bar hardening reactions in high protein bars

Formulating high protein bars is a challenge since concentrated proteins can negatively affect texture and reduce shelf life, causing the products to be unacceptable for consumers. This study examined the functionality of protein-polyphenol aggregate particles formulated with whey protein isolate (WPI) and polyphenol-rich cranberry juice (or imitation juice) in model high protein bars. Differences in texture and structure of protein bars during 43 days of storage at 32 °C were dependent on the type of protein (unmodified WPI or aggregate particle) and the drying technique (freeze-drying or spray-drying) used in particle formation. Bars prepared with WPI-cranberry spray-dried particles (WPI–C SD) were softer and less elastic than those formulated with unmodified WPI or polyphenol-free (WPI-IC FD, WPI-IC SD) particles (firmness range 0.09–0.85 kPa). Bars formulated with WPI-cranberry freeze-dried particles (WPI–C FD) were softer than control bars made with WPI; but, only up until 31 days of storage, and less elastic than control bars up until 11 days. The addition of protein-polyphenol particles not only increased the nutritional content of the protein bars, but also inhibited rheological and structural changes, and could be used as a novel approach for functional delivery of protein in the formulation of high protein bars.