Benefits and challenges of fortified beverage systems with brewer’s spent grain-derived protein isolates.

Abstract

Plant protein-based soft drinks offer a combination of hydration and enhanced nutritional value and align with current consumer preferences for health and sustainability. While plant-based protein consumption continues to increase, fortification of soft drinks with protein is a challenge due to protein aggregation and precipitation in an acidic environment. EverPro™ (EP) is a barley and rice protein isolate (BRPI), upcycled from brewers spent grain (BSG) with a substantial solubility across a range of pH values. This study evaluated the effects of two different barley and rice protein isolates, EverPro™ Dark Fraction (EDF) and a decolourised version, EverPro™ Light Fraction (ELF), at ingredient inclusion levels of 0%, 2.5%, 5% and 10% in diverse beverage systems including water, apple juice, a full sugar and sugar free carbonated drink, a sweetened ice tea, an unsweetened black tea and a non-alcoholic beer. A comprehensive analysis was performed to assess physicochemical and functional properties, including pH, viscosity, density, turbidity, stability, particle size, foaming and tribology. Increasing the addition of both ingredients elevated pH, viscosity, and density, as well as lubrication properties of all beverages. These functionalities were interlinked with ELF exhibiting higher values compared to EDF. Beverage turbidity, stability and particle size of the protein dispersions were influenced by changes in pH, resulting from the addition of EverPro™ ingredients. Trends revealed that beverages tended to be less turbid and more stable at pH levels further from the ingredients’ isoelectric points (pH ~3.4), where both EDF and ELF are known to be optimally soluble. These protein fortified beverages represent a step towards soft drinks with added nutritional benefits, compared to typical market options, and can serve as functional or sports beverages. In addition, they offer a substitute to animal-based protein soft drinks formulated from ingredients such as whey or collagen, contributing to more sustainable food systems.