Influence of viticultural and winemaking practices on wine composition and quality: research past, present and future.

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Anita Oberholster

Influence of viticultural and winemaking

practices on wine composition and quality:

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Background – phenols in wine

• Main phenols (flavonoids) in red wine

– Anthocyanins responsible for red color – Flavan‐3‐ols (ex. catechin, epicatechin) • Oligomers and polymers of flavan‐3‐ols, so called proanthocyanidins (PA) or condensed tannins Fig 1

• Extraction during wine making

– Seed PA (mDP ~ 10) – Skin PA (mDP ~ 30) – Anthocyanins from skins Anthocyanin

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Figure 1: Proanthocyanidins

Extension units

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Background – phenols in wine

• Main phenols (flavonoids) in red wine

– Anthocyanins responsible for red color – Flavan‐3‐ols (ex. catechin, epicatechin)

• Oligomers and polymers of flavan‐3‐ols, so called proanthocyanidins (PA) or condensed tannins Fig 1

• Extraction during wine making

– Seed PA (mDP ~ 10) – Skin PA (mDP ~ 30)

– Anthocyanins from skins

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Background – phenols in wine

• During wine maturation and ageing

– Anthocyanins and PA polymerise with each other by different mechanisms Fig 2 • Influenced by grape composition, presence of wood (hydrolyzable) tannins

• Sensory properties of proanthocyanidins (PA)

– Main contributors to bitterness and astringency – Ratio of astringency to bitterness increase with mDP – ‘Coarseness’ and ‘dryness’ of astringency increase with galloylation

Gawel et al. (1998) Austr. J. Grape Wine Res.(6) 74 Vidal et al. (2003) J. Sci . Food Agric. (83) 564

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Figure 2: Wine pigments

Direct condensation

Mateus et al., (2003) J. Agric. Food Chem. 51: 1919‐1923; Reynolds (2010) Managing wine quality.

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Background – phenols in wine

• During wine maturation and ageing

– Anthocyanins and PA polymerize with each other by different mechanisms Fig 2 • Influenced by grape composition, presence of wood (hydrolyzable) tannins

• Sensory properties of proanthocyanidins (PA)

– Main contributors to bitterness and astringency – Ratio of astringency to bitterness increase with mDP – ‘Coarseness’ and ‘dryness’ of astringency increase with galloylation

Gawel et al. (1998) Austr. J. Grape Wine Res.(6) 74 Vidal et al. (2003) J. Sci . Food Agric. (83) 564

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Chemical and sensory properties of red

wine pigments

• Characterization of polymeric pigments

– Comparing the polymeric pigment profile of 6 month old and 5 year old Syrah wine from the same vineyard •  conc. of polymeric pigments, methylmethine and vinyl‐linked pigments • mDP of wine 4  10 – Development of the mouth‐feel wheel Fig 3 – Determined the mouth‐feel of different white wine treatments Fig 4

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Figure 3: Mouth‐feel wheel

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Chemical and sensory properties of red

wine pigments

• Characterization of polymeric pigments

– Comparing the polymeric pigment profile of 6 month old and 5 year old Syrah wine from the same vineyard •  conc. of polymeric pigments, methylmethine and vinyl‐linked pigments • mDP of wine 4  10 – Development of the mouth‐feel wheel Fig 3 – Determined the mouth‐feel of different white wine treatments Fig 4

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Figure 4: Mouth‐feel of different

white wine treatments

Oberholster, Francis, Iland, Waters (2009) Austr. J. Grape Wine Res. (15) 59‐69

White free run juice White free run juice + anth Red wine White free run juice + white skins and seeds + anth White free run juice + white skins + seeds White free run juice + red skins and seeds W WA WS WSA WRS RS

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Mouth‐feel of different white

wine treatments

Oberholster, Francis, Iland, Waters (2009) Austr. J. Grape Wine Res. (15) 59‐69

• W: white free run juice • WA: white free run juice + anth • WS: white free run juice + white skins and seeds • WSA: white free run juice + white skins and seeds + anth • WRS: white free run juice + red skins and seeds • RS: red wine

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Saucier et al. (1997) Phytochem. 46: 229‐234; Zoeklein et al. (1995) Wine analysis and production. Chapman & Hall.

Exogenous/Commercial Tannins

• _{Commercial tannin extracted from nutgalls,}

tannin rich wood and grape seeds

(Resolution Oeno, 2002)

• _{Classification of commercial tannin}

– Condensed tannin (catechin > 50 mg/g or proanthocyanic tannin content > 0.5 mg/g) – Nutgalls (digallic acid content 4 – 8 mg/g) – Oak (scopoletine content > 4 g/g)

• _{Commercial tannin extracted with EtOH,}

water, ether or steam

(Zoecklein, 2005; Saucier et al. 1997)

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Use of Exogenous/Commercial

Tannin

• _{Tannin addition for following purposes or}

problem correction:

– Contribute to mouthfeel/taste – Protect against oxidation enzymes, – Assist to precipitate proteins, – Modify aromas including vegetative aromas – Increase aging potential – Stabilize wine color

• Few scientific publications about effect of

commercial tannin addition

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Influence of commercial tannins on red

wine phenol composition and quality

Keulder, Oberholster, Du Toit (2006)

Treatment and source Type of tannin according to the supplier

Dosage (mg/L)

Tanenol Rouge (TR) Condensed & hydrolysable 100 300

Oenotan (Oeno) Hydrolysable 100 300

QCTN Hydrolysable 100 300

Tanin VR Supra (VR S) Condensed & hydrolysable 300 500 1000

Tanin VR Supra NF (VR NF)

hydrolysable 300 500 1000

Control (Cntrl)

• Addition of different commercial tannins to wine (Merlot, Cabernet Sauvignon, Syrah) before fermentation (2004-5)

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Addition of commercial tannins to

wine after fermentation

• Effect of different phenol content wines

– Merlot and Cabernet Sauvignon (3 tannins, 100 mg/L)

» pressed at 6°Brix

» 10 days extended maceration

– No signf diffr compared with controls

– Addition of tannins did decrease diffr between wines made with and without extended maceration

• When O₂ addition (0, 3 and 8 mg/L oxygen) were combined with tannin addition

– Clear that O₂ had greater effect on phenol composition

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Micro‐oxygenation (MOX)

Del Ãlamo et al., (2010) Anal. Chim. Acta 660:92‐101. Gómez‐Plaza and Cano‐López (2011) Food Chem. 125: 1131‐1140.

• _{Used to enhance color density and}

stabilization, similar effect to barrel

maturation

• MOX before MLF 10‐30 mg/L/month,

after MLF 2‐5 mg/L/month

• O₂ penetration through the barrel estimated at 1.66 and 2.5 ml.L‐1_.month‐1 •  Color density, similar to barrel aging (Gómez‐Plaza and Cano‐López, 2011)

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Investigation of the effect of MOX

before MLF on color density

Geldenhuys, Oberholster, Du Toit (2009) Treatment Before MLF CD (AU) After MLF CD (AU) 0x Seeds control 8.9 ± 0.1a 8.3 ± 0.1a 16 mg/L 12.9 ± 0.3b _{8.7 ± 0}a 1x Seeds control 17.4 ± 0.1c 13.4 ± 0.1b 16 mg/L 19.3 ± 0.1d _{13.7 ± 0.2}b 2x Seeds control 20.9 ± 0.3e 14.9 ± 0.2g 16 mg/L 23.8 ± 0.3f _{13.8 ± 0.5}b • Effect of different oxygen dosages wines made with different grape seed concentrations after 2 months • Color density (CD) increased with amount of seeds and MOX (2 months)

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Investigation of the effect of MOX

before MLF on Pinotage wine

Geldenhuys, Oberholster, Du Toit (2009)

3.2m

Control 16 mg/L O₂ 32 mg/L O₂

• Aged for 2 months in tanks at 20 °C (68°F)

• Samples taken at different tank levels were similar • MOX improved color stabilization, no signf difference

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Fining and cross‐flow

microfiltration

• Reasons for fining

– Clarification and stability (sterilization) – Reducing wine astringency

• Filtration

• Clarification and stability (sterilization)

• Does cross‐flow microfiltration reduce

astringency?

• Replace fining

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Control Gelatin (100 mL/hL) Egg Albumin (10 g/hL) Cross‐flow microfiltration Pinotage wine after MLF • 3 Bottles per tank • Analysis: 0 and 3.5 months

Influence of fining and cross‐flow

microfiltration on Pinotage wine

Carstens, Du Toit, Oberholster (2010)

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Influence of fining and cross‐flow

microfiltration on Pinotage wine

Carstens, Du Toit, Oberholster (2010) • Fining and cross‐flow microfiltration (CF) mDP by 25% • CF removed the most color • CF only treatment perceived as different after 3.5 months of bottle aging using difference testing 0 5 10 15 20 25 30 35 40 45

Control Gelatin Egg Albumin Cross‐Flow Microfiltration

Turbidity

(NTU)

Treatments

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Oberholster, Botes, Lambrechts (2010), J. Int. Sci. Vigne Vin. Special issue Macrowine, 33‐40.

Determine opt ripeness in Cab

Sauv grapes~wine quality

• Study over 4 years in partnership with

Distell

• _{Vineyards in 4 climatic zones (}

Cabernet Sauvignon

)

• _{Sampled weekly}

• _{Measurements included color and}

phenols (RP‐HPLC, spectrophotometric)

• Grape skin extract and wine tastings

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Oberholster, Botes, Lambrechts (2010), J. Int. Sci. Vigne Vin. Special issue Macrowine, 33‐40.

Determine opt ripeness in Cab

Sauv grapes~wine quality

R2_{= 0.7376} R2 = 0.6956 R2_{= 0.6365} 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Jan 5 Jan 15 Jan 25 Feb 4 Feb 14 Feb 24 Mar 5 Mar 15 Mar 25 Apr 4

Sample date m g an th / be rry 2003 2004 2005 26°B 26°B 26°B • Strong relationship between °Brix, color and grape and wine quality • Seasonal differences result in larger variance then vineyards in different climatic zones

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Blancquaert‐Witbooi, Oberholster, Da Silva, Deloire (current)

Projects 2011‐2012

• _{Study in South Africa investigating the}

effects of temp and light on grape skin

and seed tannin composition

– Determine the tannin structure during the green berry phase and ripening phase – Determine whether the tannin structure is modified during the ripening phase by vine water status and berry water content through bunch exposure (light and temperature)

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Effect of abiotic factors on tannin

development

Shaded Exposed Exposed_+ 95% UV net Shaded + 95% UV net West Focus: Bunch microclimate, light quality, quantity and temperature Blancquaert‐Witbooi, Da Silva, Oberholster, Deloire (current)

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B

Effect of abiotic factors on tannin

development

Blancquaert‐Witbooi, Da Silva, Oberholster, Deloire (current) C A D A) STD B) STD + UV C )LRW D) LRW + UV

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Blancquaert‐Witbooi, Da Silva, Oberholster, Deloire (current)

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Effect of abiotic factors on tannin

development

Blancquaert‐Witbooi, Da Silva, Oberholster, Deloire (current) 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 STD LRW+UV mDP of Skin Tannin with Ripening mDP Date 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 STD LRW+UV Date mDP mDP of Seed Tannin with Ripening

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Projects 2011‐2012

• Study in South Africa investigating the

effects of temp and light on grape skin

and seed tannin

• _{Investigation the use of cold stabilization}

alternatives such as CMC

– Cold stabilization vs CMC addition • Sauvignon blanc and Chardonnay • Chemical panel, filterbility, tartrate stability, turbidity

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Projects 2011‐2012

• Study in South Africa investigating the

effects of temp and light on grape skin

and seed tannin

• _{Investigation the use of cold stabilization}

alternatives such as CMC, tannin

additions

• _{Study with E&J Gallo – investigating}

extraction kinetics and impact of temp

gradients in red wine making (DEB, ALW,

DOA, CB, RRB)

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Cap management

• Investigate effects of temperature gradients on cap extraction

– 12 treatments ‐ diffr pump‐over regimes, fermentation temp, cap and must temp • Evaluate spatial heterogeneity of phenolic profiles in a pilot‐scale wine fermentor with two‐phases and natural temperature gradients E&J Gallo funding

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Projects 2011‐2012

• Study in South Africa investigating the

effects of temp and light on grape skin and

seed tannin

• Investigation the use of cold stabilization

alternatives such as CMC, tannin additions

• Study with E&J Gallo – investigating

extraction kinetics and impact of temp

gradients in red wine making (DEB, ALW,

DOA, CB, RRB)

• Barrel trial investigating the effect of barrel

maturation on phenol composition and

mouth‐feel

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Barrel maturation, MOX and wood

alternatives

Barrel maturation + + + vs Stainless steel tank + O2 + staves Stainless steel tank + O₂+ chips Stainless steel tank + O₂ Stainless steel tank MOX MOX MOX + +

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• Red wine blend for 6 month maturation – 63% Cab Sauv, 27% Merlot, 10% Malbec • Analyses after 1 month of bottle aging – Phenolic profile – Tannin analysis • Isolation of tannin using SPE • Phloroglucinolysis (determine composition and mDP) • LC‐MS (identify polymeric pigment and possible ellagitannin derivatives) – UV‐vis (color intensity) – Sensory analysis • Mouth‐feel and aroma • Preference testing

Barrel maturation and wood

alternatives

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• Comparing barrel maturation, micro‐

oxygenation and maturation in stainless

steel tank directly

– Investigate the influence of wood tannins and oxygen • Color intensity and stability • Polymerization reactions • Mouth‐feel properties of the wine

• Comparison between the use of wood

alternatives (staves and chips) and barrel

maturation

– Ellagitannin extraction differences into wine – Difference in mouth‐feel, aroma and quality

Barrel maturation and wood

alternatives

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• Investigating the impact of pectolytic

enzymes and commercial tannin on wine

made from different quality grapes

• Investigating the use of grape berry sugar

loading to build a predictive model for the

determination of optimal ripeness for a

specific wine style in a changing climate

• The effect of the re‐use of winery

wastewater for irrigation on soil, vine, grape

composition and wine quality

• Investigating changes in wine composition

and quality with different settings of optical

berry sorting

Future Projects

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Concluding remarks

• Running survey “Current Issues in

Managing Cost and Quality in Wine

Production”

– http:\\wineserver.ucdavis.edu/survey/ • Contact details: Anita Oberholster – RMI North, room 3146 – [email protected] – Tel: (530) 754‐4866 – http://wineserver.ucdavis.edu