The effect of high pressure on Lactococcus bacteria count in Edam rennin cheese

Abstract

This study was undertaken to examine the effect of high pressure in lactic fermentation streptococci. Cheese samples were pressurized for 5–120 min at 50–600 MPa. Single and cyclic pressure treatments were conducted at 200 and 400 MPa. After pressurization, the cheeses were determined for the number of lactic fermentation streptococci with the plate method on M17 medium. Pressurization of cheese at 50–200 MPa for 30–120 min decreased the count of lactic fermentation streptococci by 4–40%, respectively, i.e. by less than one order of magnitude. Pressurization at 400 and 600 MPa for 30–120 min was found to diminish the number of lactic fermentation streptococci by 99.9–99.9997%, i.e. to an extent similar to pasteurization. After pressurization at 400 and 600 MPa, it was found that the highest number of microorganisms was subject to inactivation in the first 5–10 min of the process. Cyclic pressurization, as compared with a single pressure treatment, exerted little effect on the extent of streptococci reduction in cheese.

Keywords:

• high-pressure processing
• lactic fermentation streptococci
• rennin cheese