Graduate Thesis Or Dissertation
 

The isolation and characterization of the pectic enzymes and the pectic substances of the Northwest strawberry

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  • Enzymic systems able to hydrolyze the compounds forming the supporting structure of plant tissues have a major effect upon the texture of fruit products. The objective of this thesis was the development of a theory to explain the textural changes in fresh and processed strawberries. The presence of pectinolytic enzymes and the substrates upon which they act were studied. In addition the activity of cellulase was investigated. The following conclusions were made: 1. An endopolymethylgalacturonase exists in Northwest strawberries which catalyzes the hydrolysis of pectins, pectates and protopectins. 2. The strawberry endopolymethylgalacturonase indicated a maximum activity at pH values between 4.5 and 5.5. 3. The degree of methylation of the substrate did not appear to have an influence upon the activity of the enzymes. This enzyme demonstrated the same rate of action upon Na pectate and citrus pectin. 4. Sodium chloride solutions at concentrations up to 0.50 M and calcium ion at concentration 0.01 M did not show any effect on the activity of the strawberry endopolymethylgalacturonase in citrate buffer at pH 5.0. 5. The strawberry endopolymethylgalacturonase was inactivated after heating at 212°F for approximately 35 minutes in citrate buffer at pH 5.0. 6. Non-enzymic hydrolysis of the strawberry pectic substances occurs and hydrolysis is more pronounced at lower pH values. 7. The pectinesterase activity in Northwest strawberry is low in comparison with tomato fruits. The optimum activity of strawberry P.E. occurred at pH 7.5. 8. While cellulase activity existed in Northwest strawberries, the strawberry cellulase did not hydrolyze the insoluble strawberry cellulose.
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Déclaration de droits
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