Microwave-assisted acidic hydrolysis of phytate from rye bran – Experimental procedure and model prediction

Phytate is an abundant phosphorus (P) compound in plant material, which cannot be taken up by monogastric animals but is to a significant part released into the environment with excreta. In order to make use of cereals' phytate content, phytate hydrolysis by microwave-assisted thermal treatment of an acidic rye bran extract into inorganic phosphate was investigated experimentally and by modelling for process application. A phytate conversion of 98.5% could be achieved at 200 °C and 15 min reaction time and showed to be highly dependent on the temperature by a sigmoidal correlation. Treatment time showed its main influence in the mid temperature range (between 150 and 180 °C), thus didn't play a role anymore at beginning hydrolysis and towards full conversion. A mathematical quartic model represented phytate conversion with an optimum at harshest examined conditions and allows for predictions of the hydrolysis within the parameter range investigated. A kinetic model gives parameters of reaction order 0.68 and an activation energy of 118.7 kJ/mol with the option to predict phytate hydrolysis beyond the investigated parameter range and for varying input concentration. Equal liberation of all six phosphate groups from phytate is mechanistically suggested. Both model approaches show comparable results.