Abstract #M17

# M17
Maintaining high level of intact casein in Cheddar cheese during aging.
B. M. Riebel*1, S. Govindasamy-Lucey2, J. J. Jaeggi2, M. E. Johnson2, J. A. Lucey1,2, 1University of Wisconsin-Madison, Madison, WI, 2Wisconsin Center for Dairy Research, Madison, WI.

As Cheddar cheese ripens, intact casein is broken down. High levels of intact casein are desirable if the cheese is to be used for processed cheese. Our goal was to minimize ripening changes using 4 strategies: (1) use of milk containing higher casein, (2) minimizing the amount of rennet used by up to 50%, (3) using camel chymosin as the rennet, as it is less proteolytic than the calf chymosin currently used, (4) use of high pressure processing (HPP) applied to the cheese shortly after manufacture. Cheddar cheese was made from ultrafiltered (UF) milk. The cheesemilk protein and casein contents of were ~5.15% and 4.30%, respectively. Three types of cheeses were made each using different levels of rennet: (a) control, which had 2.0μL rennet/50g milk, (b) 25% reduced, and (c) 50% reduced. To determine the optimal amount of rennet for the control, coagulation tests were run on the UF milk using small strain dynamic rheology. The targeted coagulation time for all treatments was 20–30 min. To decrease coagulation time as rennet levels decreased, we added calcium chloride and varied coagulation temperatures. We determined the coagulation temperatures to be 32.4°C, 35.2°C, and 37.8°C for the control rennet, 25% reduced and 50% reduced samples, respectively. During cheesemaking, a licensed cheesemaker used these coagulation temperatures and maintained a high draining pH. Cheeses had similar moisture contents (~37%). Four days after the cheese was made, half of the samples from each vat were saved as natural cheese base and the other half underwent HPP at 600 MPa for 3 min. Hardness was measured by texture profile analysis and loss tangent (LT) values were measured by heating cheese during small strain oscillatory rheology. At 4 d, there was a decrease in hardness with a decrease in rennet level, but no impact of HPP treatment on hardness. For the max LT value, HPP treatment resulted in an increase in the LT max, but decreasing rennet level had little impact. Cheeses will be aged for 8 mo and will be made into processed cheese at 2 week, 2, 4, 6, and 8 mo time points to determine changes in the performance of the cheese base over time.

Key Words: intact casein, high pressure processing, cheese ripening