Chemistry, sensory, chemometrics and development capacity
Access to advanced and highly specialised equipment and staff is essential for the high quality, multidisciplinary research which is a trademark of the AWRI, and for collaborative projects with other research organisations and industry partners. This is especially the case where projects require access to highly specialised technical and scientific skills, such as those of a synthetic organic chemist or sensory scientist. In addition, the provision of sensory analysis requires a pool of screened, trained and experienced sensory assessors operating under the leadership and supervision of a professional sensory specialist who tracks performance and assesses training needs. Before and after a sensory experiment, highly specialised skills in experimental design, software for the acquisition of complex sensory data, data analysis and interpretation are required. Similarly, complex chemical analysis requires specialised analytical chemists with expertise in modern chromatography and mass spectrometry as well as skills in method development, optimisation and validation to produce reliable, accurate and precise data, and to ensure instrumentation remains operational around the clock.
Sensory science involves great care in experimental design; panel recruitment using qualified judges; careful control of all aspects of the test procedure; leadership and people skills to ensure judges are highly motivated and unbiased; and a high degree of knowledge of aspects of psychology, physiology, statistics and wine science. The AWRI runs four main types of sensory testing: an expert technical quality panel, trained sensory descriptive analysis, difference testing and consumer hedonic testing.
The technical quality panel provides detailed tasting notes, as well as fault scores, for wines submitted through AWRI helpdesk investigations, as preliminary screenings for research projects, and for clients of AWRI Commercial Services. During 2014/2015, the panel evaluated 214 wines in formal sessions, as well as numerous training samples, and more than 300 wines in preliminary bench tastings. The 18 judges on this panel have extensive general wine tasting expertise and technical knowledge of wine production and composition, with most having commercial industry experience, formal oenology qualifications and/ or having completed the AWRI Advanced Wine Assessment Course. All judges, no matter how experienced, are required to pass a probationary period before being admitted as reportable judges.
In 2014/2015 22 major descriptive analysis studies were completed using the AWRI’s highly trained part-time external sensory panel – the highest number of such studies ever completed in a year at the AWRI. After two to four weeks of panel training and assessments the judges rate the intensity of carefully selected, defined appearance, aroma and flavour attributes over multiple replicated occasions. The sensory profiles generated provide invaluable information regarding the effect of viticultural or winemaking treatments; knowledge of key wine components giving rise to flavour characteristics; consumers’ drivers of liking; and the influence of closures or storage on wine sensory properties. Assessor performance is continually monitored after completion of each project, with the ability to discriminate, degree of agreement with other panellists, and repeatability carefully assessed and tracked over time. In addition, training exercises including identification, ranking and rating tests with tastes and odours are conducted at regular intervals, with the performance of individuals in these tasks recorded and monitored. The studies included two large projects with SARDI assessing the effect of grapevine clone on wine flavour, with Chardonnay and Shiraz wines made from grapes from vineyards in Victoria, South Australia and Western Australia. As part of helpdesk investigations, the sensory properties of several problem wines were evaluated; while several sets of wines bottled under different closures were assessed, including a Shiraz wine that had been bottled for 48 months. Multiple sets of wines that had been shipped to the UK in bulk transport were evaluated to determine whether shipping routes or conditions had a sensory effect. The techniques of Time-Intensity and Temporal Dominance of Sensations (TDS), two methods providing data on the time course perception of sensory properties, were also applied, with Dr Pascal Schlich from INRA Centre des Sciences du Goût et de l’Alimentation in Dijon, France, running a workshop on TDS with the AWRI for Waite Campus staff and industry personnel.
Difference testing, generally using the method of triangle testing, is also an important sensory technique to find if a treatment has had a perceptible effect on wine aroma or flavour. Approximately 50 AWRI staff are screened and qualified to perform this task, usually assessing two or three sets of wines per session. Fifteen sessions were completed, including tests to find if sooty mould had a sensory effect on wine flavour at different levels. Investigations were also made into the efficiency of the tetrad difference test procedure, where it was confirmed that this method of assessing a set of four wines is not as sensitive as the triangle test.
Consumer testing for degree of liking has been conducted with three major studies, involving more than 350 consumers in total. The studies investigated consumer preferences for commercial Cabernet Sauvignon wines with varied ‘green’ flavour and mouth-feel characteristics; for commercial Viognier and Chardonnay wines with differing ‘apricot’ and ‘peach’ flavour; and for unoaked Chardonnay wines made under pilot-scale conditions from juices sourced from different regions across Australia with different degrees of ‘tropical fruit’ sensory attributes. An improved registration and recruitment procedure has been developed, so that a greatly increased number of qualified consumers are now on the AWRI database.
Spectral measures of grape and wine composition
The application of mid-infrared, near infrared, ultraviolet and visible spectroscopy has continued to be important for research projects and for contract studies at the AWRI. Fingerprinting the spectral signature of samples for authentication purposes, and for assessing wine style or grade, has been a key element of studies over the last 12 months. In addition, assistance has been provided to a University of Adelaide project led by Prof. Eileen Scott for rapid assessment of powdery mildew.
Synthetic organic chemistry
The synthesis of important analytical standards and other chemical compounds required for mechanistic studies or sensory investigations is of great benefit to the AWRI’s research. When compounds are not available commercially, or are prohibitively expensive, the ability to produce them in-house is invaluable. Projects requiring synthesised compounds have included those investigating ‘stone fruit’ flavour, inmouth flavour release and sulfur off-flavours.
Aroma compound analysis
State-of-the-art analytical instruments, including GC-MS and LC-MS, are carefully looked after to ensure they are in optimal operational order and capable of being used continuously in periods of high demand to give timely results. The suite of analyses that is available continues to expand, with newly published methods available this year for varietal thiol compounds including the compound involved in ‘struck flint’ aroma, benzyl mercaptan, as well as a range of volatiles implicated in oxidative off-flavour, notably phenyl acetaldehyde and methional. Accurate and precise analytical methods for targeted aroma compounds have been applied in many projects. Important compounds such as norisoprenoids (‘fruity’, ‘violets’, ‘kerosene’), thiols (‘tropical fruit’, ‘box hedge’), monoterpenes (‘citrus’, ‘floral’), rotundone (‘pepper’) and C6 compounds (‘green’, ‘grassy’) have been quantified in more than 500 samples. These analyses are also available on a fee-paying basis through AWRI Commercial Services.
Metabolomics (South Australian Metabolomics Facility) The AWRI established the South Australian node of Metabolomics Australia in 2008 with funding from Bioplatforms Australia and the South Australian State Government that enabled the purchase of five dedicated GC-MS and HPLC-MS instruments. The South Australian Metabolomics Facility is part of a national network with partners in WA, Victoria and Queensland who support and service private and public sector R&D in their respective states. It operates as a collaborative service platform, providing access to infrastructure and specialist expertise to academia and industry across all interested sectors.
During 2014/2015, the South Australian Metabolomics facility provided approximately 7,500 analyses on more than 3,500 samples for a diverse range of clients from the environmental, biomedical and agri-food sectors. New HPLC-MS methods allowed the identification and quantification of corynetoxins in grains and detection of sulfur compounds and their precursors in wine. In addition, optimisation and extension of existing methods continued, for example for HPLC-MS analysis of guaiacol glycosides in support of smoke taint diagnostic services; volatile acids in fermentation products by GC-MS; and non-volatile metabolite profiling in diverse biological matrices using an automatised derivatisation reaction in combination with GC-MS. Ongoing collaborations exist with the University of Adelaide and with Fondazione Edmund Mach in Italy.