Phytic acid in faba bean : the effect of pH, soaking time and heat-treatment to reduce the phytic acid content offaba bean

Abstract: To feed a globally growing population, a challenging shift in the usage of today’s food system is required. This includes a shift towards more sustainable human diets, with increased levels of protein from plant-based sources. Faba bean (Vicia faba L.) is a potentially attractive candidate to fulfil this purpose, not the least because of its qualitative nutrient content, but also for its cultivation potential in Sweden. However, faba beans have varying levels of antinutrients, including phytic acid. Phytic acid has metal chelating abilities with the potential to cause mineral deficiencies in humans. The compound can be reduced by different pre-treatments and processing techniques, such as soaking for various times in altered pH conditions and temperatures. This master thesis had three aims. The first was to develop and optimise a method to evaluate the concentration of phytic acid in faba bean, variety Tiffany. The second was to identify and evaluate the effect of soaking treatment conditions, i.e., pH, soaking time and heat-treatment, with the purpose to minimize the concentration of phytic acid in the legume. Finally, the third aim was to establish the optimum treatment based on the conditions of the soaking treatments. The faba bean proteins were extracted with alkaline extraction followed by isoelectric precipitation and differential NaCl solubility. The phytic acid was extracted and analysed using anion-exchange chromatography and a colorimetric method with Wade reagent. The optimised method successfully evaluated the concentration of phytic acid throughout the protein extraction of faba bean, resulting in a 28 % reduction. All soaking treatments reduced the concentration of phytic acid. These results provide important indications of processing information on phytic acid in faba bean for the industry of plant-based foods. The optimum soaking treatment was treatment E, with a pH value of 6 at a temperature of 20 °C for 2 h. Treatment E reduced the concentration of phytic acid by 87 %.