Time: 12:05–12:55
Location: Room 205, Babcock Hall
Coffee / tea will be served starting ~11:45 outside room 205
This seminar will be presented by Maggie Becher.
ABSTRACT
Impact of baking temperatures, rennet type, and manufacturing style (without starters) on extending the squeakiness shelf-life of fresh cheese curds
M. A. Becher1, S. Govindasamy-Lucey2, J. J. Jaeggi2, M. E. Johnson2, Brandon G. Prochaska2, G. Nike Gnanateja1, J. A. Lucey1,2
1University of Wisconsin–Madison, Madison, WI, 2Wisconsin Center for Dairy Research, Madison, WI
Squeakiness is a prominent attribute in fresh cheese curds; however, it quickly disappears (4-5 d) after the cheese curds are made. The squeak is produced when the elastic protein matrix rubs against the teeth while the consumer is chewing. Fresh cheese curds also develop a softer structure over time, indicating a weakening of the protein matrix, so we hypothesized that the changes in texture and squeakiness attributes are correlated. To prolong the performance shelf-life of fresh cheese curds (squeakiness and texture), we utilized treatments that would retain the protein structure by reducing acidification and proteolytic activity. Our curds were manufactured similarly to another squeaky cheese, Juustoleipä (Juusto), or “bread cheese,” which is not acidified (manufactured without starter cultures) and is baked after manufacture. These “Juusto” curds were manufactured using two types of rennet, one with a lower deactivation temperature (R1) and the other with a lower proteolytic activity during storage (R2). The curds made from both coagulants were then split into 3 baking temperatures: not baked (NB), baked to a low internal curd temperature (60°C, LB), and baked to a high internal curd temperature (88°C, HB). The Juusto curds were then analyzed at 2 d, 1, 2 wk, and 1, 2 mo of refrigerated storage. The analyses included cheese composition at 1 wk, pH, proteolysis (pH 4.6-soluble nitrogen), textural, rheological, and sensory properties. We also developed a new audio method for quantifying squeakiness, where we recorded audio and used machine learning approaches to classify the recordings as “squeaky” or not. The HB curds had lower moisture contents than the NB and LB treatments and therefore had higher protein, fat, and total Ca content due to higher moisture loss during the higher baking temperatures used. This led to higher initial hardness levels which did not decrease during storage whereas the NB and LB samples both softened over time due to high levels of proteolysis. The HB curds retained a higher ratio of elastic to viscous bonds (higher storage modulus and lower creep compliance values) by 2 mo of storage, compared to the other treatments. The HB curds also maintained a higher level of squeakiness as evaluated by a trained sensory panel (still processing audio data), and the squeakiness was almost completely gone after 2 mo of storage in the NB curds. The higher level of proteolysis in the NB curds likely contributed to the bitterness, softening, and loss of squeakiness by 2 mo of storage. While we are still collecting and processing the data, the different rennet types did not impact the squeakiness attribute as evaluated by the trained panelists. These results showed the impact of proteolysis on reducing the squeakiness attribute and pose potential solutions to extend the performance shelf-life of fresh cheese curds.
