High hydrostatic pressure improves the functionality of dietary fibre in okara by-product from soybean

The combined effect of high hydrostatic pressure (HHP) and controlled temperature on total (TDF), soluble dietary fibre (SDF) content, and its associated hydration properties were assayed in okara, a rich-in-insoluble dietary fibre residue from the soydrink- and tofu-making process of soybean. TDF in starting unprocessed okara was 45.7% and its SDF to TDF ratio was 4.6. When dry, hydrated and autoclaved okara samples, were subjected to HHP-treatment (200 and 400 MPa) at 30 and 60 degrees C, the amount of SDF went up by more than 8-fold. At 200 MPa, TDF was not significantly different from control, but at 400 MPa values varied from 38.1 to 64.8%. In vitro physicochemical properties of okara were also modified by HHP-treatment. Therefore, the effect of a combined treatment with hydration, temperature and HHP-technology on the improvement of the soluble fibre fraction (%) and functionality of certain vegetable by-products from the food industry could be very useful for the elaboration of food ingredients with potential health-promoting effects. Industrial relevance: This article deals with the effect of HHP-treatment on dietary fibre fractions and associated physicochemical properties in okara by-product from soybean. Results suggested that the higher the hydrostatic pressure and temperature applied, the higher the ratio of soluble to total dietary fibre in okara. Likewise, the effect of combined hydration, mild temperature, and HHP-treatment could increase the soluble fraction (%) of other rich-in-insoluble dietary fibre vegetable by-products, which could potentially be used as valuable ingredients of new functional foods. (C) 2010 Elsevier Ltd. All rights reserved.