The purpose of the present invention lies on providing a natural food preservative including chitosan, which is excellently dissolved, as active ingredient. The present invention includes following steps of: producing chitosans of multiple forms by differentiating the time and temperatures of reactions between insoluble chitosan and caustic soda； obtaining time-differentiated enzymatic reactants by applying chitosanase into each chitosan produced earlier； obtaining chitosan with excellent antibiotic properties by evaluating each enzymatic reactant obtained earlier； obtaining a mixture by mixing the chitosan obtained earlier with grapefruit seed extract, citric acid, cinnamon spirits extract and dextrin； and lyophilizing the mixture. [Reference numerals] (AA) Sorbic acid 300 ppm； (BB) Freezing 0.5%； (CC) Freezing 1.0%； (DD) Viable cell； (EE) Storage time (day)본 발명은 키토산을 유효성분으로 함유하는 식품 보존제 및 그의 제조방법을 제공함으로써 식품보존제용 천연 동결건조분말 및 액상 제품을 제공하는 뛰어난 효과가 있다.
