Isoflavone extraction from okara using water as extractant.

We here report on the use of water as a 'green' extraction solvent for the isolation of isoflavones from okara, a by-product of soymilk production. At a low liquid-to-solid ratio of 20 to 1 and 20 °C, 47% of the isoflavones that can be extracted with 70% aqueous ethanol were extracted. The malonyl-glucosides were fully recovered with a ratio of 20 to 1, while ß-glucosides were recovered with an increased liquid-to-solid ratio of 40 to 1. The extraction of aglycones was better at higher ratios, but leveled off before reaching a 100% yield. Temperature hardly affected the total amount of isoflavones. At a 20 to 1 ratio, 20 °C, and pH 10, there was no significant difference (p>0.05) between isoflavone extraction in water and in 70% aqueous ethanol. The results suggest that water may be used as a green alternative for separation of isoflavones from okara.

Pressure-temperature phase diagrams of maize starches with different amylose contents.

The amylose/amylopectin ratio in starch granules has a distinct impact on the physicochemical properties of starches. In this study the effects of high pressure and temperature combinations on the gelatinization of four maize starches with different amylose contents were investigated in an excess of water (90% w/w). Microscopy was used to determine the loss of birefringence in starch granules. Experiments were undertaken in the pressure range of 0.1-750 MPa and temperature range of 30-110 degrees C, holding the conditions constant for 5 min. Temperature and pressure stabilities of high amylose starches were found to be significantly higher than those of waxy and normal maize starch. Thermodynamic models are proposed to describe the loss in birefringence as a function of pressure and temperature. From the pressure-temperature phase diagrams constructed it was evident that maize starch gelatinization is not accelerated at pressures below 300-400 MPa. However, at higher pressures the threshold temperature to initiate starch granule hydration and gelatinization is significantly reduced for all starches investigated. This study extends the knowledge of the impact of high pressure on food components and will possibly make the technology more attractive to use as a substitute for or in combination with conventional food-processing methods.