Use of Recombinant Chymosin in the Manufacture of Cheddar and Colby Cheese

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Abstract
Recombinant chymosin purified from E. coli K12 (Genencor Inc.) was examined for its suitability to manufacture Cheddar cheese. Commercial calf rennet or recombinant chymosin with and without Bacillus subtilis cellular homonogenate was used to determine if enzyme sources affected Cheddar cheese quality or yield. Cheese was evaluated at 3 and 6 mo of age. Purified enzyme was mixed with cellular extracts from B. subtilis at approximately one and four times the protein concentration in the initial homogenates. Cellular materials did not affect clot times, cheese quality, or inhibit cheese acid development. No differences were noted between the yields of Colby cheese manufactured with calf rennet and recombinant chymosin. Initial Cheddar cheese manufactured with recombinant chymosin were excessively bitter, typical of cheese retaining excessive amounts of proteases. Dilution of purified prochymosin preparations increased total enzymic activity 2.7 times. Evidently, the purified recombinant preparations contained some oligomers that because active after being incorporated into the cheese mass, causing bitter flavors to develop during aging. Diluted enzyme preparations were used successfully in the manufacture of Cheddar cheese.