Preparation, characterisation and physicochemical properties of the phosphate modified peanut protein obtained from Arachin Conarachin L.

The objective of this work is to obtain a new phosphate modified peanut protein (PMPP) with good physicochemical properties by using a simple and reliable method. For this purpose, response surface methodology (RSM), based on a Box-Behnken design, was used to optimise conditions for the microwave-assisted formation of phosphate modified peanut protein isolate (PPI) with sodium tripolyphosphate (STP) as the substrate. The results indicate that emulsification activity index (EAI) was optimised at 65.04 m(2)/g under the following conditions: substrate mass fraction of 10%, initial pH of 9.90, STP mass fraction of 7.70%, microwave power of 800 W, reaction temperature of 43.0 °C, and incubation time of 3.15 min. The emulsification activity of PPI improved after phosphate modification. Phosphatisation of both the Ser and Thr hydroxyl groups and the Lys amino groups was confirmed for the reaction between STP and PPI according to analysis of FTIR, XRD, TG/DTA, NMR-(31)P and SEM of the product. Physicochemical properties of PMPP were better than those of PPI.