In fact, throughout the Edo Period, brewing of sake was a risky business facing always with possibility of decaying its products, and, therefore, it may be reasonable to consider that shochu spirit was added to sake wine in order to increase its proof and prevent its corruption.
じっさいに江戸時代を通じて、酒造りは腐造の危険と背中合わせのリスクの多い事業であったため、腐造を防ぐためアルコール度数を高めるべく、焼酎を酒に添加していたと考えられる。