Upcycling soy processing waste (okara) into structured emulsions for fat replacement in sweet bread

Okara is the main waste of soy processing and represents a large economic and environmental burden. Nevertheless, the fibre and protein content of okara supports the upcycling of this critical waste. This study aimed at assessing the potentialities of okara as an innovative oil-structuring ingredient.

Structured emulsions containing up to 520 g oil kg^-1 and having oil holding capacity higher than 75% were prepared by high-shear mixing of okara with liquid oil. Microstructural analysis showed that the oil phase was evenly distributed in the okara matrix, probably due to the emulsification ability of the okara fibre-protein network. The performance of okara structured emulsions as palm margarine replacer were tested in the preparation of sweet bread. Okara emulsions (500 g oil kg^-1 ) resulted not only in a significant reduction of saturated fatty acids (>50%), but also in an increased protein and fibre content. Compared to the use of liquid oil solely, okara emulsions allowed reducing the oil released from bread loaf. Bread containing okara emulsion also presented physical and sensory properties similar to those of palm margarine bread, the only exception being a more perceivable oiliness and rancid defect, which are, however, easily preventable by applying appropriate formulation strategies.

The use of okara as innovative ingredient for oil structuring would answer the current demand for sustainable heathy diets, based on clean-label foods with low-saturated fat content, and increased protein and fibre supply. This approach would also allow the complete upcycling of this critical waste. © 2022 Society of Chemical Industry.