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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Methods for presenting raspberry and strawberry samples to the Hunter color and color-difference meter

Tinsley, Ian J., 1929- 29 April 1955 (has links)
Graduation date: 1955

The influence of enzymes on color deterioration of strawberry juice and concentrate

Lee, Dai-lih Doris 01 March 1979 (has links)
Graduation date: 1979

Polyphenol oxidase of D'Anjou pears (Pyrus communis L.)

Halim, David Husien 17 September 1976 (has links)
Stability, substrate and inhibitor specificity and electrophoretic properties of a crude polyphenol oxidase (PPO) preparation extracted from d'Anjou pears (Pyrus communis L.) were investigated. Levels of polyvinylpyrrolidone and pH of buffer for extraction were found to affect the specific activity of the extracted enzyme. An extract prepared with 1.5 g insoluble PVP per 15 g fresh tissue in acetate buffer (pH 5.6) resulted in the highest PPO specific activity of the crude extract. Addition of PVP did not affect the electrophoretic patterns of PPO isozymes. The pH optimum of PPO occurs at 7.0. Heat inactivation of PPO followed first order kinetics and approximately 50% of PPO activity was inactivated after heating for 11.7, 6.25, 2.25 and 1.1 min at temperature of 70°,75°,80° and 85°C, respectively. The crude PPO enzyme was active towards o-dihydroxyphenols, but inactive towards monophenols. Disc electrophoresis on 7% polyacrylamide gels revealed eight active isozymes towards catechol, 4-methylcatechol, chlorogenic acid, caffeic acid, dopamine, d-catechin and DL-dopa. Similar electrophoretic patterns were observed with all substrates. No differences in the band patterns were observed between a fresh crude PPO preparation, a frozen crude extract and a dialyzed extract when catechol was used as substrate. L-cysteine, diethyldithiocarbamate, thiourea, metabisulfite, cyanide, mercaptoethanol and ascorbic acid inhibited the enzyme activity. L-cysteine and diethyldithiocarbamate were the most effective inhibitors. / Graduation date: 1977

Chlorophyllase involvement in color development of valencia oranges: (Citrus sinensis L. Osbeck)

Aljuburi, Hameed January 1979 (has links)
No description available.

The degradation, in model systems, of the anthocyanin of the Marshall strawberry

Tinsley, Ian J., 1929- 08 April 1958 (has links)
Graduation date: 1958

Changes in raspberry pigments during processing and storage

Daravingas, George Vasilios 14 May 1963 (has links)
The retention of pigments in processed raspberries is a function of the process method and conditions of subsequent storage. The presence of sucrose and the nature of the headspace gas also influences the retention of the pigment. The effect of some of the above variables on the pigments was investigated. Variables imposed were: (1) concentration of syrup, (2) headspace gas atmosphere, (3) temperature, and (4) time of storage. Separation of the pigment of Willamette red raspberries and black raspberries was made by column chromatography and the pigments were analyzed. spectrophotometrically. The results showed the following: 1. The pigments of Willamette red raspberries consisted of four separate cyanins as based on the R [subscript f] values and characteristic wavelengths of maximum absorption. The pigments of black raspberries consisted of three fractions. 2. On the basis of R [subscript f] values and wavelengths of maximum absorption only two of the constituent fractions were the same. 3. The wavelength of maximum absorption of all the anthocyanins shifted towards shorter wavelengths after the first month of storage. 4. Time and temperature of storage and their interaction each contributed significantly to the destruction of the cyanin pigments. An increase in either variable resulted in a greater destruction of the pigments. 5. As the concentration of the ingoing syrup was increased, the amount of individual cyanins decreased. 6. Oxygen in the headspace gas was shown to be detrimental to the retention of the cyanins I, II, and IV of the Willamette raspberries and to cyanins II and III of the black raspberries. 7. Changes in the total pigment concentration were greatly influenced by the cyanin in greatest concentration in the species. 8. Heat processing destroyed approximately 20 percent of the pigments of the raspberries. / Graduation date: 1963

Color estimation of frozen strawberries by reflectionmeter, spectrophotometer, and visual grading

Shah, Jayantilal Nemchand 04 December 1950 (has links)
Graduation date: 1951

Color changes in berries during processing and storage

Gizis, Evangelos John 16 May 1962 (has links)
Graduation date: 1962

Relationship between visual grades and instrumental color determinations of frozen strawberries

Shah, Jayantilal Nemchand 08 May 1953 (has links)
Graduation date: 1953

Die invloed van kalsiumtoedienings op polifenoloksidase, peroksidase, sekere fenoliese verbindings en aspekte van die ultrastruktuur van avokadovrugte

Van Der Merwe, Pierre Johan 11 February 2014 (has links)
M.Sc. / Please refer to full text to view abstract

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