In order to promote the prevention of microbial and enzymatic spoilage and to retain the freshness, sweet persimmons harvested in Gyeongsangnam-do were treated with grapefruit seed extract(GFSE)-CaCO₃ mixture and stored in the proper packaging conditions. A low concentration of GFSE showed effective growth inhibition of plant pathological bacteria and fungi, Enterobacter pyrinus and Fusarium sp., which were involved in the decay of fruits and vegetables. GFSE was stable to heat treatment; its antimicrobial activity was not changed by heat treatment upto 100℃. However, when the temperature was raised to 120℃, about 90% of total activity was retained within 30 min. GFSE was also highly stable to broad pH changes; its activity was not changed in the range of pH 2.0 to pH 12.0. The physiological function of cell membrane in the spores of Bacillus cereus and the hyphae of Fusarium sp. was destroyed by treating with GFSE. It was observed that treating sweet persimmons with GFSE mixture and storing them in strech-wrapped packages could prolong the freshness of sweet persimmons and reduce quality deterioration.