Wageningen University, Wageningen, Netherlands
With rapid population growth, more plant-based products are needed in the market currently with a sustainable production chain. However, to produce ingredients for plant-based products, conventional approach always aims at separating the plant protein materials into their pure constituents, which requires large water and solvent quantities. This reduces the sustainability of plant protein production, leading to the opposite effect than the initial purpose. Mild fractionation is an aqueous fractionation process for the production of plant protein ingredients in which oil extraction, carbohydrate separation using alcohol and several washing steps are omitted. Thus, exploring mild fractionation can be the potential solution for further increasing the sustainability of plant-based products.
In this study, soybean was selected as raw material and mild fractionation process was used to obtain soy protein fractions (SPFs) with different pH (3.5, 4.5, 5.5, 6.5 and 7.5). Water-holding capacity (WHC), nitrogen solubility index (NSI), denaturation behaviours and rheological behaviours were compared to study the relationship between functional properties of SPFs and processing pH. All the SPFs showed relatively similar composition as commercial SPI, and proteins present kept their native state after fractionation with pH adjustment. SPFs adjusted at pH 4.5 and 5.5formed powdery texture after drying and exhibited the lowest nitrogen solubility index (NSI), water holding capacity (WHC) and viscosity. Significant different results were observed at processing pH away from the isoelectric point (pI) in both sides. The texture of these SPFs gradually transformed into flaky shape. Overall, the combination of mild fractionation process and adjustment step can be designed to achieve different functional properties of soy protein for various applications.