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Causative factors of color deterioration in strawberry preserves during processing and storageAbers, Julie Ellen 16 June 1977 (has links)
An effort was made to determine what factors are responsible for
differences in color quality between preserves commercially manufactured
from Hood and Tioga strawberry varieties.
Color analyses made on Hood and Tioga preserves, during a 26 week
storage period, included spectral measurements of aqueous extracts
from the preserve samples. In addition, Hunter color coordinates were
determined for both the insoluble residues (remaining after extraction)
and the intact preserve samples. Color analyses revealed that color
deterioration occurred at a much faster rate in Tioga preserves than
in Hood preserves, and that this deterioration was due to a faster rate
of browning in Tioga preserves.
Complete chemical analyses of fruit revealed striking compositional
differences between Hood and Tioga varieties. The concentrations of
free amino acids and metal ions were found to be similar in both varieties.
Ascorbic acid, which is believed by many to contribute significantly
to color deterioration, was actually present in lower concentration
in the Tioga variety. Anthocyanins were present in greater amounts in the Hood variety, while leucoanthocyanins, flavanols and total
phenolics were higher in Tiogas. Recent work, primarily with wine
and model wine systems, has shown that leucoanthocyanins, catechins,
and possibly other reactive phenolics, will react with anthocyanins to
form polymeric pigments. The results of this study are supportive of
the hypothesis that a similar reaction in preserves (between anthocyanins
and other phenolics) is responsible for color deterioration during
storage. / Graduation date: 1978
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Purification of strawberry polyphenol oxidase and its role in anthocyanin degradationWesche-Ebeling, Pedro Alfredo E. 30 August 1983 (has links)
Polyphenol oxidase (PPO) from strawberries was purified,
partially characterized, and used to study its role in the degradation
of anthocyanin pigments. The extraction method included the use of a
buffered solution containing the phenolic binders Polyclar AT and
Amberlite XAD-4. Addition of Triton X-100 resulted in an increase of
the extracted activity. Higher levels of PPO activity were obtained
using citrate rather than acetate in the buffer. This was possibly due
to the capacity of citrate to chelate calcium ions, and, therefore, to
inhibit crosslinking of the pectic polymers which would trap the
enzyme. Using a Phenyl Sepharose CL-4B (PS) hydrophobic column two
fractions of the enzyme, Fl and F2, were separated from the pectic
material and the bulk of the 280 nm absorbing material.
PP0-F1 obtained from the PS column was less hydrophobic than F2,
and showed a molecular weight of 111,000 by gel filtration on
Sephacryl S-300. Form Fl eluted in the void volume of an anion
exchange column and did not penetrate into the running gel during
electrophoresis. The binding of PP0-F1 to a Concanavalin-Agarose
(ConA) column demonstrated the presence of carbohydrate associated
with the enzyme. PP0-F2 showed a molecular weight of 34,500 and could be resolved by anion exchange chromatography into one large peak and a
smaller one at its shoulder. Fraction F2 of the enzyme resolved into
two bands during electrophoresis, and did not bind to the ConA column,
Both fractions of the enzyme showed multiple banding on lithium
dodecyl sulfate -- polyacrylamide gradient gels.
Both fractions of the enzyme obtained from the PS column showed
very high activity in the presence of D-catechin. The Michaelis
constants for D-catechin for PPO fractions Fl and F2 were 0.50mM and
O.4lmM respectively, and the maximum velocity 82,700 and 18,800 nmoles
0₂ per min per ml respectively. D-catechin in the presence of
PP0-F1 was rapidly oxidized and the resulting solution had a maximum
absorption at 390 nm. When D-catechin and PP0-F1 were combined in
model systems with either pure cyanin or pelargonin, an absorbance
peak at 390 nm was noticed with increased absorbance in the region of
the anthocyanin pigments. After 24 hr, 50% of the pelargonidin and 60%
of the cyanin was destroyed and a brown precipitate was formed. PPO-Fl
seemed to oxidize cyanin at a very slow rate but did not oxidize
pelargonin. It was suggested that the anthocyanin pigments were
destroyed by either the direct oxidation by the quinones formed from
D-catechin by PPO, or that the anthocyanin pigments were
co-polymerized into the brown polymeric pigment, tannin, formed from
D-catechin-quinone polymerization. / Graduation date: 1984
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Yield component and growth analysis of strawberries /Olsen, Jeffery L. January 1983 (has links)
Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 55-62). Also available online.
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Analysis of intermediate carbon metabolism in strawberry plants /Basson, Carin Elizabeth. January 2008 (has links)
Thesis (MSc)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.
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Preliminary breeding studies with the strawberryRoberts, Ray Harland 01 June 1912 (has links)
Graduation date: 1912
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An evaluation of methods of estimating 1953 costs of producing strawberries /Quincy, Walter Levi. January 1955 (has links)
Thesis (M.S.)--Oregon State College, 1955. / Typescript. Includes bibliographical references (leaves 41-42). Also available online.
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The relative importance of various factors influencing profits in strawberry production,Peacock, Neal Dow, January 1939 (has links)
Thesis (PH. D.)--Michigan State College of Agriculture and Applied Science, 1937. / Technical bulletin no. 162, February 1939, of the Michigan Agricultural Experiment Station, Lansing, with cover having thesis note. eContent provider-neutral record in process. Description based on print version record.
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Micropropagation of fruit crops with emphasis on strawberryDe Assis, Marcio. January 1977 (has links)
Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 69-80).
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Host and vector relationships of strawberry viruses in WisconsinDuffus, James E. January 1955 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 99-103).
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External growth responses and anatomy of strawberry (Fragaria vesca L.) affected with several virusesHaltvick, E. T. January 1962 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 41-45).
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