Novel plant protein sources for the beverage sector: technological functionality, nutritional properties, sensory characteristics, and consumer acceptability

This Ph.D. Thesis aims to define a strategic approach for the development of functional coffee powders enriched with plant proteins and intended for espresso or filter coffee brewing. To this aim, a funnel logic was applied to rationally select plant protein ingredients presenting high solubility and sensory attributes ascribable to typical coffee flavor and aroma. To collect relevant information regarding the effect of plant source, ingredient purity, and processing methods, on the functional properties of plant protein, a literature review was performed, and based on the acquired data, commercial protein-rich plant ingredients were scouted on the market. Scouted ingredients were highly pure in protein and presented low solubility and unpleasant sensory attributes. Based on these issues, the possibility to apply technological strategies to overcome these issues was studied. The use of food industry legume by-products (okara from soymilk production and substandard peas form canned industry) was selected as a possible way of improving the environmental sustainability of protein-rich ingredients. To this aim, a novel drying technology based on solvent exchange and supercritical-CO2-drying was studied to turn okara and peas into whole powders rich in plant proteins, while reducing plant off-flavors and off-colors. Despite many advantages, these powders presented low solubility, making them not adequate for coffee protein enrichment. Chemical and/or physical strategies were thus applied after protein extraction to improve solubility. To this aim, pH-shift and/or high-pressure homogenization were demonstrated tosignificantly improve not only solubility but also foaming and emulsifying properties. Finally, the ingredients scouted on the market or developed in this Thesis were tested for their suitability in the development of protein-rich filter and espresso coffee. The addition of selected plant protein-rich ingredients allowed to obtain filter and espresso coffee prototypes without distorting the typical coffee flavor and aroma. The combination of different plant protein ingredients as well as the use of dark roasted Robusta coffee blends resulted as winning strategies to increase plant protein content in the brews.