In this paper the antibacterial effect of tannin in vitro and its influencing factors are investigated. The minimal inhibitory concentration is measured through the agar dilution

and the antimicrobial properties are screened by filter disc method in food system. By using agar-comparing method

various antibacterial factors in food system such as pH value

sodium chloride concentration

sucrose concentration

metal ions and organic acids

on its bacteriostatic effect are screened. The results show that tannins have good antibacterial activities on

Staphylococcus aureus

and

Micrococcus luteus

MIC of which is 0.39 mg/mL and 0.09 mg/mL respectively. Under the condition of acid

or under the synergism of citric acid and lactic acid

the antibacterial effects of tannic acid on food spoilage organisms increase

; and the bacteriostatic effects are stable for NaCl

sucrose and metal ion. Compared with potassium sorbate

it seems to have a better effect on food and the MIC of which is lower than potassium sorbate. Tannins with organic acid together are more conducive to the antibacterial activity

which have a wide pH range. With added salt and sugar food

tannins can weaken the use of salt or sugar

and be beneficial for healthy living.