Highlights of the Year 2002
- Publication of the outcomes of the Institute's major wine
closure trial in July 2001 resulted in unprecedented media
attention, both from industry publications and mainstream print
and electronic media in Australia and overseas. The published
data has provided objective information on which media
commentators have been able to pursue the debate on the relative
merits of various types of wine closure.
- Using stable isotope labeled analogues of important wine
flavour/aroma compounds, the issue of flavour scalping by
closures is being addressed. A preliminary analysis of data for
wines that have been stored in bottle for two years has indicated
that different types of closures vary considerably in their
capacity to absorb flavour compounds from wine.
- Thirty stable isotope labelled analogues of important
fermentation volatiles have been synthesised for use in
developing new analytical methods for compounds which contribute
to wine flavour.
- A new precursor to trihydrodimethylnaphtalene (TDN), which
confers kerosene-like characters to aged Riesling wine, has been
identified. This knowledge is a prerequisite to better control
the development of this character in Riesling.
- A rapid and non-destructive method to measure wine colour was
developed. The sample port of a common UV-Vis spectrophotometer
was inexpensively modified to enable the insertion of different
bottle sizes. In non-coloured glass bottles (Flint) the full
visible spectrum range of 350 to 700 nm can be determined. Whilst
the full range cannot be determined in the coloured glass
bottles, it is possible to determine A 420 nm in French green
(pale yellow glass), emerald green and cobalt blue bottles, and
by correlation with A 540 nm, in amber (brown glass) and antique
green (dull yellow brown glass) bottles.
- Visual comparisons between pairs of white wines to which
ascorbic acid was or was not added at bottling have called into
question the universal value of A 420 nm (‘yellow’)
as an indicator of brown colour in wines. Wines to which ascorbic
acid was added had the higher instrumentally measured browning (A
420 nm) but were not visually assessed as the browner wine. This
information points to a need for a careful reassessment of
conclusions based on A 420 measurements in relation to the pros
and cons of ascorbic acid use in white winemaking.
- Using HPLC and mass spectrometric methods, numerous
potentially hitherto unknown red pigments could be detected in
wine samples and the presence of hitherto unknown large tannins
in grape seeds was demonstrated.
- In the 2002 vintage, the first highly integrated large scale
winemaking trials were performed that successfully linked our
tannin and anthocyanin research with microbiological studies
focused on the fermentation properties of S. bayanus, and
included experiments on the feasibility of Near Infrared
Spectroscopy (NIRS) for fermentation monitoring.
- The application of the ‘mouth-feel wheel’ was
extended to the formal descriptive sensory analysis of several
wines from viticultural and winemaking trials. The sensory
studies included trials on the effect of canopy architecture, sun
exposure and irrigation practices on Shiraz wine, as well
as assessments of the impact of powdery mildew infection on the
sensory properties of Chardonnay wine, and the identification of
mouthfeel differences between Cabernet Sauvignon wines made in
the 2001 vintage with S. cerevisiae and S. bayanus
yeasts.
- With advanced sensory studies based on an incomplete
factorial design the primary and interactive effects of
proanthocyanidin (‘tannin’) concentration, ethanol,
anthocyanins and wine polysaccharides on the mouth-feel
perception of wine like media were explored.
- The NIRS technique continues to show promise as
a useful tool for the industry and several companies are
furthering their adoption of the technology into their business
activities. Institute staff are assisting the Cooperative
Research Centre for Viticulture's commercialisation activities in
further field-proving trials to assist transfer to the broader
industry. Commercialisation trials conducted during the 2002
vintage highlighted the significant challenges with both
standardisation of the instruments and transfer and robustness of
calibrations.
- The evaluation of an NIRS instrument that can rapidly scan
whole intact grape berries indicated that the technique was
feasible but with the cost of lower accuracy compared to scanning
of homogenates of grape berries.
- The NIRS technique has shown promise as a means of rapid
measurement of the concentrations of malvidin 3-glucoside,
pigmented polymer, tannin, and gallic acid for monitoring their
evolution during red wine fermentations.
- Preliminary trials with the FT-IR (Fourier Transform
Infrared) spectroscopy technique using a novel sample
presentation device (attenuated total reflectance, ATR) showed
promise in providing correlative measurement of compounds that
are present in relatively low concentration in grapes.
- Further analysis of the role of a
Saccharomyces bayanus yeast in red wine production
compared with a conventional Saccharomyces cerevisiae
yeast has shown that S. bayanus can modify wine flavour
not only by affecting the aroma profile, but also by affecting
palate and colour through altering the anthocyanin and pigmented
‘polymers’ content. Appraisal of wines from the 2001
vintage by several winemaking teams has led to a more extensive
evaluation during the 2002 vintage.
- Application of the laboratory model system for predicting the
effect of fermentation yeast on malolactic bacteria to 84
combinations of 21 yeasts and four bacteria has shown that: 1)
Compatibility between yeast strain and bacteria strain depended
on the combination of strains involved; and 2) The majority of
yeasts were compatible with the four bacteria strains, however,
one bacteria strain revealed a higher proportion of
incompatibility reactions than the other three strains,
suggesting that specific combinations of yeast and bacteria could
be chosen for promoting or retarding MLF.
- A study of the precursor compounds required to
produce mousy off-flavour by Dekkera/Brettanomyces yeast
and heterofermentative lactic acid bacteria has revealed several
factors that could be used to control off-flavour formation in
addition to those which prevent biomass formation, and include
controlling residual sugar and, oxygen in the case of
Dekkera/Brettanomyces yeast and ferrous ions in the case
of heterofermentative lactic acid bacteria.
- A laboratory-scale red wine fermentation system
that can produce wine with comparable colour measurements as
achieved on the winery scale has been developed. Using this
fermentation system it could be shown that yeast strain clearly
had an affect on wine colour, irrespective of the region from
which the grapes were sourced.
- Interspecies hybrids between commercial Saccharomyces
cerevisiae wine strains and strains from all the other
Saccharomyces sensu stricto species, including
Saccharomyces bayanus, have been produced. Several of
these hybrids have been used in laboratory scale winemaking and
commercial winemaking trials where they have been shown to
ferment grape juice at rates comparable to commercial wine
strains. Sensory analysis by Institute staff and company
winemakers indicates that the hybrids have the potential to
impart diverse aromas and flavours to wine.
- The identity of genes that code for haze protective factors
(HPFs; mannoproteins with haze protective activity) has been
unambiguously confirmed. This now gives us the ability to
prepare larger quantities of these active materials for pilot
scale trials. Studies with these ‘HPF’ genes also
show that these genes may have some impact on the ability of
yeast to tolerate cold and ethanol. This is an unexpected bonus
and illustrates the serendipitous nature of research.
- Combined heat and proteolytic enzymatic treatment of white
wines to remove heat unstable protein and reduce bentonite
requirements appears to be a promising procedure for commercial
application. Wines with and without enzyme addition were heated
at 90ºC for 1 minute, then immediately cooled to 16ºC
to 19ºC in a tubular heat exchanger. This combined heat and
enzyme treatment, or heat treatment alone, reduced the protein
levels and bentonite-fining requirements but had negligible
effect on aroma and no effect on palate characteristics.
- 72 workshops held at AWITC were coordinated by Institute
staff, with several workshops being presented by Institute staff
(see Appendix 1).
- A 'Roadshow' visit was made to Queensland in November 2001.
Six senior Institute staff presented a full-day seminar, and
Industry Services staff presented two full day seminars
concurrently, on each of two days.
- 546 separate wine industry technical problems were
investigated during the year, resulting in the analysis of 1223
individual samples, and formal reports on the investigations and
advice on avoiding re occurrence of the problems, was provided to
the industry practitioners concerned.
- The eleventh Australian Wine Industry Technical
ConferenceÔ was successfully held in Adelaide with a record
number of delegates registered (1,678 delegates). The formal
program was presented by 57 speakers and Chairs, 72 workshops
were held, 134 posters were displayed and 178 exhibitors
participated in the Trade Exhibition.
- 56% increase in requests for information was fielded by staff
of the John Fornachon Memorial Library (3,363 requests).
- The Library’s local searchable database now indexes
over 44,000 scientific and technical reprint articles.
- The web-accessible database (available only to Australian
wine and grape levy payers) doubled in size during the year and
now comprises approximately 20,000 records from relevant trade
and research publications and proceedings.
- The Institute published 28 papers on Institute activities in
refereed and non-refereed publications within Australia and
internationally.
- Institute staff gave 78 invited oral presentations in
Australia and overseas.
- 29 workshops and 44 posters were presented in Australia and
internationally.
- Institute staff presented 50 lectures and coordinated a six
week subject to undergraduate students.
- Institute staff supervised 27 postgraduate students and
supervised the completion of five theses.
- Institute staff provided a free advice and problem-solving
service to Australian winemakers including responding to some
1,600 enquiries from industry.
- Overall, Institute staff responded to 5,720 requests for
information during the 2001/2002 year or, to put the statistics
into perspective, last year 22 people contacted the Institute
seeking information on every working day of the year. This
figure does not include request for work through the Analytical
Service.
- The Viticulturist responded to 566 enquiries of which
approximately 75% were related to agrochemicals.
- 9000 copies of the Institute’s annual publication,
Agrochemicals registered for use in Australian Viticulture
2002/2003 were produced and increased demand has required an
additional print run.
- The Institute, in conjunction with The Alfred and Monash
University, secured funding from the GWRDC for a new two-year
project entitled ‘The identification and measurement of
potential allergens in wine’
- The Institute publication, Analytical specifications for
the export of Australian wine, was republished with
information for 47 export destinations
- Institute staff assisted in the development of National Wine
Centre exhibits.
