Effect Of Hydrostatic High Pressure Treatment On Fatty Acid Content And Dielectric Properties Of Cheddar Cheese

In this study, taking the cheddar cheese samples treated by hydrostatic high pressure as treatment group and untreated as the control group, we studied effect of hydrostatic high pressures on maturity characteristics and fatty acid content changes of cheddar cheese. Treatment pressure were 200MPa,400MPa and 600MPa respectively and the holding time was 5min and 15min respectively for each pressure grous. All the samples were stored at 9℃. In the ripening times of 7d,14d,21d,30d,45d,60d,90d, the physical and chemical properties (including fat content, pH value), ripening indexes (pH4.6-WSN/TN), dielectric property parameters and fatty acid contents were measured. The test frequencies of dielectric property selected were 0.2GHz and 2.45GHz. The fatty acid contents were measured by gas chromatograph. The results showed as follows:(1) Under the test frequencies of 0.2GHz and 2.45GHz, the relative dielectric constants for the group of control and the group treated by 200 MPa and 400 MPa increased with extension of the the ripening time of cheese samples. However, the relative dielectric constant for the sample treated by 600MPa showed a slight reduction trend.(2)The total fatty acid content for the groups both control and treatment increased firstly and then decreased during the ripening period of 0-90d and the highest peak appeared in between 30d-45d. The total content of fatty acids for the treatment of 200MPa decreased after 45d, that for the treatments of 400MPa and 600 MPa decreased after 30d. and that for the control group the total fatty acid content decreased after 60d.(3)The ripening indexes expressed by pH4.6-WSN/TN for both control and treatment group increased steeply before 30d, and the change leveled off after 30d. The ripening indexes of the treatment group was higher than that of the control group.(4)As the extension of the ripening time of cheddar cheese, the pH value increased and then the pH value decreased. The hydrostatic high pressure tyreatment and the ripening time all had extremely significant effect on pH of the cheese (P<0.01). Comparing with the control group, The fat content change of the hydrostatic high pressure treatment group shwed an extreamly significant difference (P<0.01).(5)The experimental results showed that the dielectric constant and the total fatty acid content for all the groups showed less correlated relations.