Utilization of enzymes to provide heating endpoint markers and modify endogenous cholesterol in muscle foods /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Twenty-four glycolytic, tricarboxylic acid cycle or lysosomal enzyme activities were evaluated from two types of bovine, porcine and avian muscles in unheated water extracts using standard analytical methods at room temperature. The enzymes included: adenylate kinase (AK), L-alanine dehydrogenase (LAD), aldolase (ALD), carnitine acetyltransferase (CA), creatine kinase (CK), enolase (E), fructose-6-phosphate kinase (F6PK), fumarase (F), β-galactosidase (BG), glucose-6-phosphate dehydrogenase (G6PDH), glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT), glyceraldehyde-3-phosphate dehydrogenase (G3PDH), glycerol-3-phosphate dehydrogenase (GOHDH), hexokinase (H), isocitrate dehydrogenase (ICDH), leucine aminopeptidase (LAP), malate dehydrogenase (MDH), alkaline phosphatase (ALP), phosphoglucoisomerase (PGI), phosphoglucomutase (PGM), pyruvate kinase (PK), transaldolase (TA), and triosephosphate isomerase (TPI). Minimum spectrophotometric detection limits were established and enzymes found with activity above these limits were subsequently examined at different heating endpoints in ground tissue and water extracted homogenates. In bovine muscle, CK, E, G3PDH, MDH, PGI, PGM, and PK, underwent rapid denaturation between 60°-72°C when monitored in 2°C increments and heated at a rate ~3°C/min at pH 6.8. In homogenized extracts of porcine muscle at pH 6.8, E, MDH, F6PK, PK, CK, ALD and TPI displayed sharp inactivation points near the federally regulated endpoint temperature of 68.8°C for imported pork and pork products. ALD, CK, E, F6PK, GPT, MDH and PGI from avian muscles showed significant (P < 0.05) declines in activity or complete loss of activity at an endpoint temperature range of 66°-68°C or 72°-74°C (E) when monitored at 2°C intervals. Some muscle-to-muscle enzyme activity differences in unheated or heat treated samples were noted for each species. Enzyme denaturation and resultant loss of activity was accelerated by heat treatment in ground samples. Species differences in enzyme activity were observed in both unheated and heated muscles for some enzymes. Cholesterol oxidase was shown to decrease the amount of cholesterol by 94% after reaction for 12 h in finely ground bovine muscles slurries. Longer reaction times did not result in further decreases of cholesterol. Addition of PLC to aid in oxidation of membrane bound cholesterol provided inconclusive results. Unbuffered muscle/water slurries at pH 5.50-5.65 provided an adequate reaction environment for the enzymatic oxidation of cholesterol. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Food Science and Technology." |
| Physical Description: | xiv, 222 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |