STUDIES ON PHENOLASB AND PHENOLICS IN GRAPES
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Date
1988
Authors
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Publisher
Mahatma Phule Krishi Vidyapeeth, Rahuri.
Abstract
The present investigation was undertaken to study
the biochemical differences in three cultivars of grapes
viz; Thompson Seedless, Cheema Sahebi and Anab-e-Shahi
during development and storage. The developing berries
of these cultivars were collected at 30, 45, 60 and 75
days after flowering and at 4, 8, 12 and 16 days after
harvest. Grape berries at different stages of development
and storage were analysed for physico-chemical and bio
chemical parameters viz; colour, taste, size, moisture,
titratable acidity, pH, total soluble solids, reducing
sugars, soluble proteins, total phenols, anthocyanins
and polyphenoloxidase (or phenolase) activity.
During development, the colour of berries changed
from green to yellow or golden yellow and the taste
changed from sour to sweet. The weight and volume of berries' increased during development. Moisture content,
titratable acidity and total phenols of the berries
decreased, while pH, total soluble solids, reducing
sugars, soluble proteins, anthocyanins and phenolase
activity increased during development. The effects of
enzyme concentration, substrate concentration, pH and
temperature on the activity of crude preparation of poly
phenoloxidase were studied.
Among the three cultivars studied, the levels of
total soluble solids, TSS/acidity ratio, reducing sugars,
anthocyanins and phenolase activity were found to be
relatively higher and those of berry size, moisture,
titratable acidity, pH, soluble proteins and total
phenols were found to be lower in the developing berries
of Thompson Seedless than the other two varieties. Corre
lation studies revealed that sugars and anthocyanins,
polyphenoioxidase and anthocyanins were positively
correlated while, sugars and total phenols, total phenols
and anthocyanins, total phenols and polyphenoioxidase
activity were negatively correlated during development
of grape berries.
During storage, the colour of berries changed to
dark yellow and taste changed to sour. The weight,
volume, moisture content, total soluble solids, TSS/
acidity ratio, pH, reducing sugars, soluble proteins, anthocyanins and total phenols in grape berries decreased
while titratable acidity and polyphenoloxidase activity
increased during storage.
Among the three cultivars studied, the levels of
TSS, TSS/acidity ratio, reducing sugars, anthocyanins and
phenolase activity were found to be relatively higher and
those of berry size, moisture, titratable acidity, pH,
soluble proteins and total phenols were relatively lower
in Thompson Seedless variety than the other two varieties
during the storage of grapes.
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