Abstract
The objective of this study was to evaluate the elect hics. that homogenization of concentrated culture at high pressures would have on the growth, survival, and enzyme activity of lactic starter culture and to determine 'the homogenized starter culture could be used to accelerate the ripening of Cheddar cheese. Starter culture concentrate was subjected to homogenization at 60 and 90 MPa for 1, 3, 6, and 9 cycles at an inital temperature of [100C]. The peptidase activity, lactic culture survival, and acid producing ability of the homogenized cultures were determined. Starter culture homogenized at 90 MPa was added to Cheddar cheese slurries at 0, 10, and 15% (w/w). The slurries were incubated at 4, 25, and [40OC] and proteolysis was measured every 48 hours for 10 days. Homogenization increased endopeptidase, general aminopeptidase, and aminopeptidase A activity of the homogenized culture with greatest activity observed after homogenization at 90 MPa and nine cycles. Acid production was lowest for cultures homogenized at 90 MPa for six and nine cycles. Lactic acid production was absent for up to 24 hours in reconstituted nonfat dry milk inoculated with starter culture homogenized for 9 cycles at 90 MPa. [logia til' U/ml 01] Culture homogenized [aWU lvlra IOr >] cycles was reduced 8 [logily CnJ'/InI]. Proteolysis was higher in the treated slurries than in the control with more proteolysis observed at 40 than at 25 or [4OC]. Rapid proteolysis was observed in the samples stored at [400C] but these samples developed unacceptable flavor during storage. Proteolysis in the slurries stored for two days at [40@C] was similar to the degree of proteolysis in a commercial sample of aged Cheddar cheese. Proteolysis increased during storage for samples stored at [40C] at a lower rate than the sample stored at [40@C], but was equivalent to the proteolysis determined in a commercial sample of aged Cheddar cheese after ten days of storage.
Gonzalez Ortiz, Monica Lizeth (1998). Effect of high pressure homogenization on lactic acid starter culture and the accelerated ripening of Cheddar cheese. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -G667.