Identifying semi-polar co-passengers in commercial plant protein ingredients

One of the main challenges in the transition from animal to plant proteins is the presence of undesired non-volatile co-passengers in plant protein ingredients, including off-tastants. Despite this, data on the non-volatile composition of commercial plant protein concentrates and isolates is lacking. Therefore, our main aim was to systematically identify and quantify the semi-polar co-passengers present in commercial soy, pea, oat, potato, and almond protein isolates or concentrates. Our RP-UHPLC-MS analysis of the semi-polar co-passengers in the plant protein ingredients indicated that saponin content varied: 0.105 g/kg, 0.270-0.595 g/kg, and 0.891-1.096 g/kg, for oat, pea, and soy, respectively. Additionally, potato protein isolates contained trace amounts of glycoalkaloids. Other semi-polar co-passengers in the investigated plant protein ingredients were mainly polar lipids, comprising oxylipins, lysophosphatidylethanolamines, and lysophosphatidylcholines. We conclude that saponins, lysophospholipids, and oxylipins are the main undesired semi-polar non-volatile co-passengers in commercial plant protein ingredients.