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Commercial production of essential oils from blackcurrants (Ribes nigrum L.)

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Kerslake, Mark F (1984) Commercial production of essential oils from blackcurrants (Ribes nigrum L.). PhD thesis, University of Tasmania.

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Abstract

The aim of the research programme was to investigate factors .
influencing the production of extracts from blackcurrant buds. The
results, indicate that a small, but viable production unit could be
established within the framework of a broader essential oils industry
in Tasmania.
Various agronomic factors which influence the growth of blackcurrant
crops were examined in a systematic fan design. Investigations
for a source of bud material revealed that blackcurrant plants pruned
each winter to ground level, provide the maximum bud yields. In this
system, the blackcurrant bush will remain vegetative. The importance
of maintaining a healthy balance between plant vigour and bud yield.
needs to be appreciated, as the annual pruning regimen can potentially'
subject the plant to physiological stress and reduce bud yields in,
subsequent years.
The form of the bud yield-plant density response is asymptotic as
determined by non-linear regression analysis. Further, investigation.
of the relationship of total cane fresh weight and shoot numbers per
plant to planting density revealed that plant site is decreased at high
densities. Growth depression is observed, with respect to shoot length
at both high and low planting densities. This is discussed in terms
of competition for resources, in particular light. Basal cane girth is
Shown to be related to yield parameters and is suggested as being a reliable estimator of plant productivity.
Two canopy types are distinguished over the range of planting
densities examined. The continuous, uniform canopy at high densities
intercepts light more efficiently than the discontinuous, clumped
canopy observed at low planting densities. The continuous canopy
meets criteria laid down for an ideal canopy. In particular, it
reaches maximum size quickly, before incident radiation reaches its
summer peak, as well as being easy to maintain at maturity.
The compositional and organoleptic methods used on a number of
varieties in this assessment reveal White Bud as the preferred variety.
This analysis confirms the relationships established by Todd in his
identification key, based on phenotypic features.
Scanning electron microscopy identified, late November - early
December, as the period of most rapid increase in oil gland size. Gas
chromatographic methods reveal that the rate of oil synthesis increases
in early to mid January, corresponding to a period of increased photosynthate
availability as leaf growth slowed.
Investigation of oil quality during bud burst, under both glasshouse
and field conditions, showed that the strength of the catty note
increases as the buds break from dormancy. This raises questions concerning
the complexity of biosynthetic changes that are occurring,
particularly the relationship between terpene synthesis and abscisic
acid. Components in blackcurrant bud oil were analysed by liquid chromatography
on silica gel or florisil columns using a series of different
polarity solvents. The catty note was not eluted using these techniques,
however a reversed phase procedure employing High Performance Liquid
Chromatography was successful in separating this compound. Compositional
data and identification were obtained by gas chromatographic and mass spectrometry methods. One hundred and twenty-three components were
detected, of which sixty-six were positively identified, and good
quality mass spectra presented for fifty-seven unknowns. Some twenty-
three components reported have not been previously identified in blackcurrant
bud or fruit oils.
Gas chromatographic effluent odours were associated with the
corresponding peaks to determine their individual contribution to the
overall aroma complex. Five regions of the aroma profile were shown
to be important to the blackcurrant bud aroma, but the individual
components were not identified.
Various extraction solvents were investigated, and petroleum
ether was shown to produce an extract resembling the French product.
The superiority of liquid carbon dioxide extracts was demonstrated,
and these hold much promise for future commercial operations.
Both harvesting techniques examined were effective in removing
buds. However, the mechanical harvester is better adapted for commercial
operation due to lower labour inputs. This prototype consisted of a
set of rotating brush rollers which act to lift the bud and break the
petiole. Other rollers control the speed at which the cane passes these
brushes. In contrast, the chemical method utilizes sprays of ethephon
to cause abscission layer formation in the bud petiole.
An economic analysis was undertaken, examining the effect of price,
planting density and harvesting method on the internal rate of return of
capital invested. A mechanical harvesting operation is preferable,
returning a higher profit margin than manual harvesting, since the latter
requires high labour inputs. Lower planting densities, than those considered
desirable for agronomic reasons, are more profitable due to
reduced establishment costs.

Item Type: Thesis (PhD)
Keywords: European black currant, Essences and essential oils
Copyright Holders: The Author
Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1984. Bibliography: leaf 263-280

Date Deposited: 19 Dec 2014 02:29
Last Modified: 11 Mar 2016 05:56
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