SAUVIGNON BLANC AROMA PROFILE MODULATION FROM RATES AND SENSORY HIGH FINING
Purpose of the chapter:
The reduction of linalool and hexan-1-ol from the use of activated carbon in the Juice Fraction Fining trail was of interest to the winemakers involved. Hence, another trial was performed to ascertain if an increase in fining rate used resulted in a parallel increase of these trends. Although there are strict EU regulations for the amount of fining agent that can be used, a winery may over-fine a section of juice and then blend it with another to bring the overall fining level back into agreeance with these regulations. Photos relating to this chapter can be found in the thesis appendix.
Status of the chapter:
This chapter has been accepted for publication in the Australian Journal of Grape and Wine Research (Wiley), and is currently available in the Early View section of the journals website. Parish, K.J. et al., Sauvignon blanc aroma and sensory profile modulation from high fining rates, Australian Journal of Grape and Wine Research. Version of Record online: 3 MAY 2017 | DOI: 10.1111/ajgw.12281. The co-authorship form is available at the start of this thesis, following on from the acknowledgements section.
Sauvignon blanc is a well-known staple for the New Zealand wine industry, accounting for over 60% of the 2015 harvest and over 80% of the total export volume . Of this, Marlborough is a particularly important region, with the wines typically described as exhibiting pungent tropical aromas, with indications of green capsicum and fresh cut grass . In general, premium Sauvignon blanc wines derive mainly from free-run juice. Anecdotally, winemakers have indicated that free-run (0-12 kPa) or lighter press (12-160 kPa) juices account for around 94% of the total extracted volume, with the remaining proportion deemed press fraction (PF) or heavy pressed (160-200 kPa) juice. Previously, aroma chemistry and sensory aspects of Sauvignon blanc PF juices and wines have been explored [42, 100, 198-200].
One way to alter the composition of pressed juices is through the use of fining agents. Keeping the PF separate from free-run juice can be useful for blending purposes in the wine industry . This practice may allow winemakers to tailor a fining treatment suited to PF juice by potentially applying an excessive amount of pre-fermentation fining. This may be applied to only part of a juice batch followed by blending with lesser fined juices in order to lower the overall rate of fining applied. Caution is needed, however, when applying such an approach as countries have different specifications and limits with regards to fining.
To date, several fining studies have been applied to a selection of grape cultivars. For instance, the total sum of the aroma groups, ethyl esters, alcohols, terpenes, and acetates, decreased in Parellada wines made from musts clarified with bentonite and gelatin agents . Fining of Falanghina must using several products, including carbon and gelatin, has been reported to decrease the amount of free benzyl alcohol in the wine, an effect that was observed for two yeast strains . More recently, the addition of bentonite, activated carbon or wheat gluten decreased the concentration of ethyl dodecanoate in Chardonnay wines, whereas fining with bentonite decreased the concentration of linalool in Gewürztraminer wine . Related sensory results showed Chardonnay wines to differ in spicy aroma and floral/honey taste attributes between the fining treatments; however, neither of these differed significantly compared with their respective Control wines . More recently, several plant-based proteins have been studied, one such involving proteins extracted from lentils, peas, soy, and wheat gluten. These proteins were added to Catalanesca white wines, and a protein derived from lentils was the most efficient at removing certain ester compounds .
Most studies of the influence of fining agents on wine aroma have focused mainly on the fining before or after the fermentation of free run fractions. Because of the opportunity for winemakers to thoroughly ‘clean up’ PF juice before fermentation, a set of experimental wines were produced to measure the effect of excessive pre-fermentation fining on lower value PF juices.
This study aims to provide winemakers with new knowledge on the application of fining agents at high rates to PF juices. This is achieved by demonstrating the influence of commercially available fining agents on the aroma chemistry and sensory profile of Sauvignon blanc wines made from PFs.
Materials and Methods
Chemicals and fining agents
The following materials were used in the winemaking and analytical procedures: ultra-pure water with resistivity at 17.1 MΩ cm (Barnstead Nanopure Diamond system, ThermoFisher Scientific, Waltham, MA, USA); the fining agents gelatin (Laffort, Bordeaux, France), polyvinylpolypyrrolidone (PVPP) (International Speciality Products, Wayne, NJ, USA), and activated carbon (Erbslöh, Geisenheim, Germany); potassium metabisulfite (PMS) (Enartis E, Trecate, Italy), Lalvin yeast strain EC1118 (Lallemand, Montréal, QC, Canada), Dynastart and Nutristart (Laffort), Clinitest tablets (Bayer Healthcare, Tarrytown, NY, USA), dry ice and carbon dioxide (both food grade), along with nitrogen, argon (both industrial grade), and helium (instrument grade) (BOC Gases NZ, Blenheim/Auckland, New Zealand); hydrochloric acid (HPLC grade) (AnalaR, Normapure, Lutterworth, England); methanol (HPLC grade), sodium chloride, sodium hydroxide and anhydrous sodium sulfate (purity of ≥ 98.5%) (Scharlau, Barcelona, Spain); ethyl propiolate (99%) and reagent grade butylated hydroxyanisole (Sigma-Aldrich, Castle Hill, NSW, Australia); Supelclean ENVI-18 SPE cartridges (Supelco, Castle Hill, NSW, Australia); dichloromethane (Suprasolv, Merck (Darmstadt, Germany); ACS grade absolute ethanol (ECP, Auckland, New Zealand); hexane (95%) (Merck); isopropanol (HPLC grade) to rinse the syringe between injections for the volatile thiol analysis (Unichrom, Ajax Finechem, Newmarket, New Zealand); standards, of 98% purity, 3-mercaptohexyl acetate (3MHA) (Oxford Chemicals, Hartlepool, England) and 3-mercaptohexanol (3MH) (Acros Organics, Morris Plains, NJ, USA); labelled internal standards, d2-3-mercaptohexyl acetate and d2-3-mercaptohexanol synthesised at The University of Auckland ; d3-3-isobutyl-
2-methoxypyrazine (IBMP) (CDN Isotopes, Pointe-Claire, QC, Canada), and 2-isobutyl-3-methoxypyrazine (both 99%) (Aldrich, Sheboygan Falls, WI, USA).
The analysis of other volatile aroma compounds required several deuterated internal standards from CDN Isotopes (purity ≥ 98%): d2-3-methyl-1-butyl alcohol, d3-2-phenylethyl acetate, d3-3-methylbutyl acetate, d3-n-hexyl acetate, d3-ethyl butyrate, d3-linalool, d5-2-phenyl alcohol, d11-n-hexyl alcohol, d11-ethyl hexanoate, d12-hexanal and d15-ethyl octanoate. Other internal standards used were 3,4-dimethlyphenol (99%) supplied by Aldrich, DL-3-octanol (99%) (Acros Organics), and 4-decanol (98%) (Lancaster, Pelham, NH, USA).
Several solutions were created for sensory analysis, which included the food products tartaric acid (Hansells Food Group, Auckland, New Zealand) and iodised table salt (Cerebos Foodservice, Auckland, New Zealand); absolute ethanol (99.5%) (Merck Millipore, Darmstadt, Germany), pharmaceutical grade tannic acid (Applichem, Darmstadt, Germany), and quinine sulfate (purity of 99%) (Sigma-Aldrich).
Grape harvest and winery processing
Grapes were machine harvested on the 2 April 2014 from a single block of a Wairau valley vineyard located in Marlborough, New Zealand, during which they received approximately 60 g/tonne of PMS in solution. They were then transported to the processing winery by truck, crushed, destemmed (Vaslin Bucher Delta E8, Chalonnes-sur-Loire, France), and pressed with a Bucher 350 Xpert pneumatic press (Vaslin Bucher). In total, 50.7 tonnes of grape must were introduced to the press, which then High Fining Rates extracted the juice using a press program that reached a maximum pressure of 180 kPa.
C h a p t e r 1 . G e n e r a l I n t r o d u c t i o n
1.1 The New Zealand Wine Industry
1.2 Fining Agents
1.3 Harvested Grape Transport Time
1.4 Ultra-Violet (UV) Light Exposure
1.5 Grape Transport Temperature
1.6 Aroma Compounds
1.7 Objectives of the Study
C h a p t e r 2 . J u i c e F r a c t i o n F i n i n g
2.2 Materials and Methods
2.3 Results and Discussion
2.5 Supplementary Data
2.6 Accompanying Sensory Analysis
C h a p t e r 3 . H i g h F i n i n g R a t e s
3.2 Materials and Methods
3.3 Results and Discussion
C h a p t e r 4 . I n d u s t r i a l S c a l e F i n i n g
4.1 Introduction 4.2 Materials and Methods
4.3 Results and Discussion
4.5 Supplementary Data
C h a p t e r 5 . T r a n s p o r t T i m e
5.2 Materials and Methods
5.3 Results and Discussion
C h a p t e r 6 . U V L i g h t I r r a d i a t i o n
6.2 Materials and Methods
6.3 Results and Discussion
C h a p t e r 7 . G r a p e T e m p e r a t u r e
7.2 Materials and Methods
7.3 Results and Discussion
C h a p t e r 8 . O v e r a l l C o n c l u s i o n s
8.2 Future Considerations
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