Microwave processing of sunflower achenes and its influence on their quality and enzymes activities

Stricter requirements to environmental compatibility and smaller energy-output ratio highlight the importance of implementing the super high-frequency drying of the crop seeds. The study is aimed at the development of drying optimal parameters and modes of sunflower (Helianthus annuus L.) seeds in a settled small-size conveyor microwave unit. In-gel activity of 6 functionally key enzymes (formate dehydrogenase, glutamate dehydrogenase, malate dehydrogenase, diaphorase, leucine aminopeptidase and non-specific esterases) in polyacrylamide gels after disk electrophoresis was analyzed in order to count on an additional assessment of the temperature influence caused by electromagnetic radiation of the tested drying unit on the sunflower achenes metabolism. The correlation analysis showed the existence of the statistically significant (р < 0.05) negative dependence between the seed materials heating temperature with germination energy (correlation coefficient -0.783) and achenes germination (-0.797). These two parameters (without processing 88 and 96%, respectively) began to reduce sharply when reaching the heating temperatures of 55℃ and more. Enzymes de-activation also started within this range. Considering the collected data about drying of the seed material, the optimal heating conditions were within 26-27 minutes at 800 W and heating temperature 38-40° С. With these parameters the quality of the processed seeds was preserved, and the costs for drying were relatively low (2.61 MJ per 1 kg of the water removed).