Impact of milk preacidification with CO2 on the aging and proteolysis of cheddar cheese

Abstract

To determine the influence of milk preacidification with CO2 on Cheddar cheese aging and proteolysis, cheese was manufactured from milk with and without added CO2. The experiment was replicated 3 times. Carbon dioxide (approximately 1600 ppm) was added to the cold milk, resulting in a milk pH of 5.9 at 31°C in the cheese vat. The starter and coagulant usage rates were equal for the control and CO2 treatment cheeses. The calcium content of the CO2 treatment cheese was lower, but no difference in moisture content was detected. The higher CO2 content of the treatment cheeses (337 vs. 124 ppm) was maintained throughout 6 mo of aging. In spite of having almost one and a half times the salt-in-moisture, proteolysis as measured by pH 4.6 and 12% trichloroacetic acid soluble nitrogen expressed as percentages of total nitrogen, was higher in the CO2 treatment cheeses throughout aging. The ratio of αs-casein (CN) to para-κ-CN decreased faster in the CO2 treatment cheeses than in the control cheeses, especially before refrigerated storage. No difference was detected in the ratio of β-CN to para-κ-CN between the control and CO2 treatment cheeses. Intact αs- and β-CN were found in the expressible serum (ES) from the CO2 treatment cheese as well as αs1-I-CN, but they were not detected in the ES from the control cheese. No CN was detected in the ES from the curd before the salting of either the control or CO2 treatment cheese. Higher proteolysis in the cheese made from milk preacidified with CO2 may have been due to increased substrate availability in the water phase or increased chymosin activity or retention in the cheese.