Impact of selected coagulants and starters on primary proteolysis and amino acid release related to bitterness and structure of reduced-fat Cheddar cheese.

Despite substantial research, it is still difficult to produce high quality reduced-fat Cheddar cheese. The objective of this study was to investigate how two coagulants, bovine chymosin (BC) and camel chymosin (CC) having different proteolytic activities and two starter cultures, an O-culture (O) and a thermophilic strain of Lactobacillus plus O-culture (OLb) having different abilities to release amino acids, contribute to the structure and flavour development in reduced-fat Cheddar cheese. Cheeses manufactured using the four combinations of coagulants and cultures were analysed during a 28-week ripening period for the composition of casein, peptides, free amino acids, rheological properties and for sensory properties at end of ripening. Cheeses with CC, showed less extensive primary proteolysis, lower levels of bitterness and higher stress at fracture, which correlates to a harder structure. Whereas cheeses with BC had a higher amount of peptides released by chymosin, e.g. the bitter peptide β-casein (f193-209) or by starter proteases from the chymosin-produced peptide α-CN (f1-23). BC cheeses were also judged to be softer by the sensory panel. Cheeses containing the OLb-culture had a higher amount of free amino acids and lower strain at fracture, which correlates to a shorter structure, and the peptide profiles of cheeses produced with BC and CC were rather similar after 28 weeks in contradiction to cheeses with O-culture. Replacing the traditional coagulant BC with CC reduced bitterness but increased hardness of the reduced-fat Cheddar cheese. Replacing O- with OLb-culture also reduced bitterness but resulted in a shorter structure. The results highlight tools which could be employed to alter primary proteolysis and amino acid release, respectively, for the optimisation of flavour and structure of reduced-fat cheese. [ABSTRACT FROM AUTHOR]