Confocal imaging to reveal the microstructure of soybean processing materials

Sustainable production of food products for human consumption is required to reduce negative impacts on the environment and to consumer's health. Soybeans are an excellent source of nutritive plant proteins; aqueous extraction yields part of the available oil and protein from the legume. Many studies have been conducted which detail the various processing parameters and their effects on the extraction yields, yet there is little data on the localisation of nutritive components such as oil and protein in the fibrous unextracted by-product. Here we show a novel confocal laser scanning microscopy investigation of soybean processing materials and the physical effects of thermal treatment on the materials microstructure upon aqueous extraction. Various features, more specifically oil, protein (including protein aggregation) and cell wall structures, are visualised in the fibrous by-product, soy slurry and soy extract, with their presence both in the continuous phase and within intact cotyledon cells. Thermal treatment reduced the protein extraction yield; this is shown to be a result of aggregated protein bodies in the continuous phase and within intact cotyledons cells. Knowledge of the processing material microstructures can be applied to improve extraction yields and reduce waste production.