The use of high pressure homogenization of lactic cultures for the release of cytoplasmic enzymes to enhance and accelerate Cheddar cheese flavor development /
The objective of this research was to accelerate proteolysis in Cheddar cheese slurries using homogenized whey as a source of enzymes. A peptidase assay was developed and peptidase activity was determined in milk, whey, cell free extracts of lactococci, and cells of lactococci after growth in broth...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=743273361&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The objective of this research was to accelerate proteolysis in Cheddar cheese slurries using homogenized whey as a source of enzymes. A peptidase assay was developed and peptidase activity was determined in milk, whey, cell free extracts of lactococci, and cells of lactococci after growth in broth. Peptidase activity was identified in each enzyme source but inhibition of hydrolysis of artificial substrates was noted in whey. Whey collected at draining during the manufacture of Cheddar cheese was either prechilled to 13'C or used at the collection temperature of 34'C. The whey was homogenized at pressures up to 100 NWa to free cytoplasmic enzymes from the lactococci in whey. Temperature of the whey, lactococci survival, changes in pH, and peptidolytic activities in the whey were determined after homogenization. Homogenization at low pressures increased the counts of lactococci and increased the peptidase activity in the whey. Homogenization at higher pressures decreased the peptidase activity and the counts of lactococci. The effect of homogenization of whey on cell survival and peptidase activity was independent of the number of valves used to homogenize the whey. Homogenized and unbomogenized whey was lyophilized and added to Cheddar cheese slurries at I or 2% (wt/wt) as a source of lactococcal enzymes. The slurries were analyzed on day 0, 2, 4, 6, and 8 for pH, buffering ability, lactococcal survival, peptidase activities, and casein degradation. The treatments did not affect on these parameters, but each factor except the percentage of water soluble nitrogen was significantly effected by the age of slurry. Reverse phase HPLC of the pH 4.6 soluble fraction of the cheese slurries revealed that the total number of peaks, area of the peaks, and height of the peaks increased as the age of the slurry increased but these changes were not effected by the addition of homogenized or unhomogenized whey. Fourteen peaks were selected for further analysis. Two of the peaks in the chromatograms increased immediately upon the whey additions to the slurries. Slight differences were visible in the HPLC patterns, suggesting altered casein degradation in the experimental slurries. |
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| Item Description: | Vita. "Major Subject: Food Science and Technology". |
| Physical Description: | xvii, 223 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |