MALTING OF OATS IN A PILOT-PLANT PROCESS - EFFECTS OF HEAT-TREATMENT, STORAGE AND SOAKING CONDITIONS ON PHYTATE REDUCTION

Phytate reduction in oats during malting in a pilot-plant process and soaking under optimal conditions for oat phytase was studied to investigate whether the malting process developed in the laboratory was also applicable on a large scale. The effects of different drying and storage conditions were also investigated. In malted oats that had been dried at 30 degrees C and stored frozen and entire for 1.5 months, the phytate content was reduced to 0.2 mu mol/g (99% reduction) after soaking as a flour for 17 h at 37.8 degrees C. The same soaking, repeated with oats dried at 80 degrees C and stored as whole grains at +4 degrees C for 1.5 months, reduced the phytate content to 0.3 mu mol/g (98% reduction). Prolonged storage (12 months) resulted in slower phytate hydrolysis in oats dried at 80 degrees C (92% reduction) during soaking for 17 h at 37.8 degrees C. Pre-soaking of malted oat flour for 16 h at room temperature was used to achieve pH conditions that were closer to the optimum for phytase activity, thus resulting in more efficient phytate reduction. Of the conditions studied in this report, the optimum pH for oat phytase during soaking was found to be between pH 4 and 4.5. In whole malted grains, the phytate content was reduced at most by 79% after soaking as whole kernels.