The elucidation of the structure of the red pigments of the black
raspberries. Monger variety, was achieved. The components of the
pigment of the berries were (a) cyanidin-3-glucoside, (b) cyanidin-3,
5-diglucoside, (c) cyanidin-3-diglucoside and (d) cyanidin-3-rhamnoglucosido-
5-glucoside. The elucidation was carried out after isolation,
purification, concentration and chromatographic separation of
the components. Further analysis by paper chromatographic techniques
and spectrophotometric methods were carried out on the pigments
and their products after specific chemical degradations.
The degradation of the major anthocyanin component, cyanidin-
3-diglucoside, was further studied in buffered model systems of
various pH values at 50°C. As the pH of the medium decreased
the anthocyanin stability increased. The same was true for total
crude pigment and the anthocyanin in the juice.
Nitrogen atmosphere enhanced the stability of cyanidin-3-
diglucoside as compared to an oxygen atmosphere. This held for the crude pigment and juice as well.
Cyanidin in buffered model systems at 50°C was much more
unstable than cyanidin-3-diglucoside under the same conditions. Nitrogen
atmosphere resulted in improvement of the pigment retention
over that in atmospheric conditions.
The thermal degradation of cyanidin-3-diglucoside in model
systems followed first order kinetics. The rate constants of the reaction
at various pH levels under air and nitrogen were determined.
The effect of the presence of various sugars and their degradation
products on the destruction of cyanidin-3-diglucoside was studied
in buffered model systems of pH 3.25 at 50°C. All of these additives
increased the rate of pigment destruction. No differences were revealed
among the sugars glucose, fructose, xylose and sucrose,
which were used. All reactions followed first order kinetics and
the rate constants were determined. When these reactions were
carried out in the presence of nitrogen instead of air, a marked
decrease in the rate of the pigment destruction was detected.
Ascorbic acid in model buffered systems of pH 3.25 at 50°C
markedly accelerated the destruction of cyanidin-3-diglucoside.
Metal ions and atmospheric oxygen acted synergistically with ascorbic
acid in the destruction of this anthocyanin. When the action
of either of these synergists was blocked, the stability of the pigment
was increased. EDTA was found to improve the retention of cyanidin-3-diglucoside by means of its ability to chelate the metal
ions present, thus indirectly inhibiting the effect of ascorbic acid.
When nitrogen was used instead of air, an improvement of the
stability of anthocyanin in this system resulted. The degradation
of cyanidin-3-diglucoside and the disappearance of ascorbic acid followed
the same pattern. The same observations were also true
for the anthocyanins of the juice.
Cyanidin-3-diglucoside in buffer at pH 6.5 was acted upon by
tyrosinase. This activity was low but nevertheless demonstrable.
When catechol was added to this system, a rapid decolorization of
anthocyanin was produced. This effect was further investigated and
a scheme of the enzymatic reaction was proposed.
Protocatechuic acid and tyrosine were able to couple with
cyanidin-3-diglucoside and enhance the destructive action of tyrosinase
on anthocyanins. The rate of the decolorization of the anthocyanin
was lower in these systems than in the coupling with catechol. / Graduation date: 1966
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26790 |
| Date | 30 July 1965 |
| Creators | Daravingas, George Vasilios |
| Contributors | Cain, Robert F. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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