Akshata has a capacity to attract chaitanya and shakti of all deity principles It retains the Shakti and chaitanya It emits shakti and chaitanya in all directions depending upon the requirement.
Unbroken rice grains when smeared with kumkum constitute akshata. When they are offered to a deity, the frequencies of deity generate similar fequencies in the akshatas. When any one of the two strings of a musical instrument having equal frequencies is stretched then the vibrations generated in it induce exactly similar vibrations in the other. In the same fashion when the akshatas are charged with divine frequencies then similar vibrations are generated in the store of rice grains in the house. Thus the rice which is charged with divine principle frequencies can be consumed throughout the year as holy sacrament (prasad) and thus can get benefit of frequencies of divine principles. You must have now understood the reason behind keeping the rice grains offered to a deity or those given as sacrament, in the grain store of the house.