|Abstract or Summary
- Spectrophotometric and chromatographic methods were
employed to study the principal pigments in Evergreen
blackberries and Alicante Bouschet grapes. Observations
were made on the following items:
1. Juices expressed from the grape and blackberry
2. Principal pigments isolated from the grape and
3. Wines made from the grape and blackberry.
A Coleman Universal Spectrophotometer, Model No. 11,
equipped with a single grating 35 millimicron fixed band,
was used for the spectrophotometric study. Observations
were made at the visible range of 400 millimicrons to 650
millimicrons at 50 millimicron intervals. Various concentrations
of the juices, pigments, and wines were
examined. The experiments were repeated with the samples
made alkaline to pH 9 with sodium hydroxide. Blackberry
wine mixed with 10, 20, 30, 40, and 50 per cent of grape
wine were also examined in the sane manner. Results were
shown graphically by plotting the E values against wave
lengths. It was found that solutions of the higher concentrations
always have the higher E values.
In the spectrophotometric study, an absorption peak
appeared at the 500 millimicron band in the blackberry
juice which was not observed in the case of grape juice.
The height of the peak was directly proportional to the
concentration of the juice and it was unmeasurable when
the juice was diluted to 5 per cent or lower.
When the juices were made alkaline, all of them had
the identical absorption curves except that the blackberry
had its curves in higher positions than those of grape.
Approximately twice the amount of anthocyanin pigments
were isolated from the Evergreen blackberry than
Alicante Bouschet grape. The principal pigments isolated from the blackberry were more intense in color than those from the grape. The isolated pigments of Evergreen blackberry
and Alicante ouachet grape behaved similarly under
the spectrophotometer, indicating that, qualitatively, the
same pigments were obtained from blackberry and grape
while using the same isolation procedure.
Spectrophotometric study of the wines showed that the
E values of blackberry wine were inversely proportional to
the addition of grape wine. This appeared to be true in
both acid and alkaline solutions. By adding 80 per cent of the alkali required to bring the wine to pH 9, more differences in E values between the various mixtures were observed.
During the chromatographic atudy, using corn starch as adsorption material, a green band of approximately 1 cm deep was observed in the case of grape wine, which was
absent in blackberry wine. The process of wine making
changed the quality of pigments as demonstrated in the
chromatographic adsorption tubes. The use of acid solution
and alumina adsorption mixture as studied by Hamill
and Simonds seems more promising than alkaline solution as
used in the present study for the detection of in grape wine blackberry wine.