The protein drink market reached more than $600 million wholesale in 2016 and is expected to continue to grow (Beverage Industry, May 2017). Increases in consumer interest in protein and an insurgence of new protein ingredients has led to the development of new protein based foods and beverages. Each protein ingredient has its unique set of functional and sensory properties, which can contribute to formulation challenges. In this study, the functional properties (heat stability, emulsion, viscosity, and foaming) of 30 commercial dairy- and plant- based protein powders were investigated. Based on heat stability testing at pH3, 7 protein ingredients (whey protein concentrate and isolate, milk-derived whey, potato protein, soy protein, pea protein, and rice protein) were selected for a high acid beverage application. A mango flavored beverage formula with 87% water, 7% sugar and 5% protein was chosen. All the beverages were adjusted to pH 3 with phosphoric acid before heat treatment at 82.2°C for 2min through an HTST process in a pilot plant. The beverages were cold-filled into pre-sanitized bottles and stored at 4°C. One set of beverages was stored in a higher temperature (45°C) incubator for 2 weeks to simulate an accelerated shelf life study. Rice protein beverages showed phase separation immediately after processing. Pea and soy protein beverages phase separated when stored at 45°C. Whey protein and potato protein beverages stayed stable during storage at 45°C. Changes in color (measured by a colorimeter) with storage was observed for all beverages except the rice protein beverage. Viscosity of beverages was measured by a rheometer at one day after processing and after the 45°C storage. No significant difference in viscosity was observed before and after the shelf life test of non-separated beverages. Sensory evaluation showed that the plant protein beverages had more bitter and beany flavors compared with dairy protein. Whey proteins provide better functionalities, and cleaner taste in high acid beverages. Plant proteins may need more modifications to produce improved functional characteristics and sensory properties in high acid beverages.