Green characters in wine Introduction The compounds responsible
Green characters in wine
Introduction �The compounds responsible for green aromas in fruits and vegetables have received considerable attention in recent years. Two main classes of volatile compounds, methoxypyrazines and C 6 compounds generally account for most of the green aromas that occur in grapes and wines 1
Aroma descriptors for C 6 compounds and methoxypyrazines 2 Compound Gpoup Aroma descriptors Hexanal C 6 aldehyde Green, grassy, unripe, fruit, fresh Trans-2 -hexanal Trans-2 -hexanol Trans-3 -hexanol Hexanol C 6 aldehyde C 6 alcohol Green, leaf grass Grass Fresh grass, fruity, floral, spice Cis-3 -hexanol C 6 alcohol Fresh cut grass, green, leaf 3 -isobutyl-2 -methoxypyrazines Green, peas, capsicum, earthy 3 -isopropyl-2 -methoxypyrazines Pea pod, capsicum, blanched peas 3 -sec-butyl-2 -methoxypyrazines Green, capsicum, earthy
C 6 -compounds � The C 6 -compounds derive from grape polyunsaturated fatty acids through a cascade of enzymatic reactions and called fatty acid degradation products (FADP). In berries, 62%– 95% of total FADP were located in the juice rather than berry skin. High proportions of FADP in grape variety : � in hybrids of V. thunbergii X V. vinifera (98. 1% of total volatile compounds), � in hybrids of V. amurensis X V. vinifera (93. 7% of total volatile compounds), � in V. amurensis species (98. 4% of total volatile compounds) 3. High concentration of unsaturated fatty acids are ubiquitous in plants grown under cold-climate.
The biosynthesis of C 6 compounds
�C 6 hexanols can be oxidized to aldehydes by yeast activity and not metabolized during fermentation. The C 6 aldehydes appear to be the most significant and can contribute stronger green or unripe characters to the juice and wine than their progenitor alcohols 5. Two C 6 -alcohols, (E)-3 -hexenol and (Z)-3 -hexenol, have been referred as the most important because its ratio can act as an indicator of the variety of origin 6.
� C 6 -compounds are formed during pre- fermentative steps including harvesting, transport, crushing and pressing (especially during crushing), as well as during eventual must heating or grape maceration 7. �Also known as a depletion of 1 -hexanol, (E)-3 hexenol and (Z)-3 -hexenol during the first days of fermentation that meaning that semi-anaerobic conditions results in lesser contents of the compounds when compared with anaerobic conditions.
�Methoxypyrazines(MPs ) are a class of chemical compounds that produce odors. They can be reported in grape by different ways and also in the case of the Asian Lady Beetle. When these beetle are processed with the grapes they can cause “ladybug taint” (LBT) – an off-flavour characterised by undesirable “green bell pepper”, “asparagus”, “canned beans” and “earthy/musty” aromas and flavours in wine 8. The most important MPs in wines are � 3 -isobutyl-2 -methoxypyrazine (IBMP), � 3 -sec-butyl- 2 -methoxypyrazine (SBMP), � 3 -isopropyl-2 - methoxypyrazine (IPMP).
They have extraordinarily low sensory thresholds in wine. Even though IBMP is generally more abundant than IPMP and SBMP in grapes and wine, high IPMP concentrations are also considered undesirable in most wines and have been described as having a ‘pea-asparagus’ type aroma, often associated with ‘unripe’ characteristics, earthy/musty/peanut aroma, green pepper aroma, canned green vegetable flavour and bitter taste 9.
Cabernet Sauvignon have high levels of MPs 10. Two methoxypyrazine compounds, 3 isobutyl-2 -methoxypyrazine (IBMP) and 3 isopropyl-2 -methoxypyrazine (IPMP), are considered to be important determinants of green flavours in Sauvignon blanc wines as positive varietal aromas, whereas the opposite is generally true for red wine varieties such as Cabernet Sauvignon where high levels of MPs are seen as detrimental for wine quality 11.
Location MPs in grape �IBMP in berry is located in the skins (95%), the seeds (4%) and in the pulp (1% ) 12. Biosynthesis in the grape berry starts after flowering, reaching the maximum concentration two to three weeks before veraison, after which it declines during maturation, not only in concentration, but on a per berry basis as well 13. Some studies have shown that IBMP found in the berry is synthesized by the berry itself and not transported to the berry from either the leaves or the shoots 14.
The main factors influencing to the concentration of MPs Concentration of MP in grapes is influenced by many variables: �Maturity �Sunlight exposure �Temperature �Water Status �Vine vigor �Yield 15 It has been shown that grapes and wines from cooler climatic regions contain higher concentrations of IBMP than grapes produced in warmer regions 1.
How vineyard decisions affect wine MP content Grape ripening conditions in the vineyard are primarily responsible for the methoxypyrazine content in wines 1. Canopy manipulation, including the role of light exposure, temperature and development, have all been implicated in influencing the MP composition in grapes 16. Leaf removal techniques may provide effective approaches to influence MP accumulation through increased light exposure, source/sink relationships or temperature effects.
Early leaf removal, performed 10 days after flowering, intensely reduced IBMP concentration, while the same treatments applied 40 and 60 days after flowering had a less significant effect. Leaf removal performed after veraison had little or no effect on the IBMP concentration in the grape berries 17. Pre-veraison bunch exposure is therefore crucial for reducing IBMP concentrations in grape berries at harvest, whereas light exposure after veraison does not influences IBMP degradation 18, 19.
Researchers which investigated the effects of leaf manipulation Left: the shaded treatment (no leaf and lateral shoot removal) with a mean daily PAR (photosynthetically active radiation) of 40 µmols 1 m-2. Right: the morning side exposed treatment with a mean daily PAR of 280 µmols-1 m-2.
Significantly higher concentrations of IBMP in grape observed in the shaded treatment in comparison to the morning exposed treatment. The IBMP concentrations in the wines were higher in the shaded treatment when compared to the morning side exposed treatment.
Conclusions To reduce the pyrazine level in the berry and consequently in the wine, canopy manipulation can be applied in the bunch zone by removing all the leaves and lateral shoots at a height of 30 to 40 cm above the cordon. As a result is possible to produce a more complex (fruitier) style of wine in comparison to the one dimensional (greener) style of the wine produced from the shaded treatment. In a warm/hot climate, similar results can be obtained by indirectly increasing the light in the bunch zone using modified VSP trellis systems such as the Smart Dyson 20
Winemaking procedures. 1. Pressing In a recent published study, researchers in France were able to show that MP in grapes is highly extractable in the traditional winemaking process 22, 23. Press wines have been shown to contain higher levels of MP. This suggests that a fraction of MP remains in the skins and is extracted during rigorous pressing 24.
2. Malolactic fermentation � Besides lowering the acidity, MLF also helps reduce green, vegetative flavors in the wine. In Chardonnay and Sauvignon Blanc, especially, experience has shown that ripe fruit flavors can be enhanced with MLF. Is primarily known to alter wine mouthfeel by making it more viscous (rounder, fuller). When MLF is used, it is often used on a portion of a wine lot and later blended with the non-MLF wine 21.
3. Yeast can reduce the concentrations of juice- and wine- derived aromatic compounds through both metabolic processes and sorption on the cell wall. Was investigated the capacity of yeast to affect MP concentration in wine. They examined effects on IBMP in Cabernet Sauvignon and Cabernet Franc wines, and noted differences of up to 37% (1. 53 ng/L). Lalvin BM-45, Lalvin ICV-D 80 and Enoferm CSM produced wines with the lowest IBMP concentration and Lalvin D-21 produced wines with the highest IBMP concentrations 25.
4. Thermo Flash �Heat is the new hot topic in winemaking. Fans of pre-heating say it does wonders for color and tannin extraction, deconstructing and reconstructing grape chemistry: maximize the good stuff, blow off the bad stuff. �Getting color and tannin out early give winemakers some extra options, like fermenting at cooler temperatures, using different yeast strains and doing red wine barrel fermentation simply with liquid juice that already has its cargo of pigment and tannins, not with messy grapes 26, 27.
What Flash can do for wine? Flash may be a good procedure to reduce aromas from smoke taint or other unwanted characters. Elimination of Pyrazine and Vegetal Character Mitigation of Smoke Taint in Grapes Ability to Barrel Ferment Red Grapes Elimination of Laccase, Mold or Unripe Flavors
Thermo Flash process The process occurs over two stages. Normally free run juice is removed before the must is rapidly heated to approximately 85°C, then pumped into a vacuum ( between 30 and 50 m. Bar) chamber where it rapidly drops 50°C in temperature. The vacuum causes the cells in the grape skins to burst and release anthocyanins, tannins and aroma compounds.
� The vacuum is also causes evaporation of water and other volatile components from the must. It is the ‘flash’ of the water into steam under the vacuum that lead to the process being named ‘flash release’. Normally 6– 10% of the liquid in the must is removed by the flash process, which results in the concentration of the remaining sugar, flavour and aroma components. The vapour from the must is collected using a condenser. � In Europe the condensate is returned to the must (this is a regulatory requirement); however this practice is relatively uncommon in the New World. The condensate can carry negative aromas especially if the fruit contained mouldy or other negative characters such as methoxypyrazines , however positive aromas could also be removed. But the removal of the ‘flash water’ isn’t an all or nothing decision and many winemakers choose to add back only a portion of the ‘flash water’ depending on the desired aroma profile and they usually
The effects of flash release on the mean sensory profiles of Cabernet Sauvignon grown in Bordeaux. Hollow circles are the “flash release” treated wine and the solid squares are the control.
“Flash release” �‘Flash release’ gives users a wide array of processing options. If processing efficiency is the primary aim of using the system, then the juice can be immediately pressed post processing and fermented in a liquid phase similar to white wine. However at least some skins contact is preferred during fermentation (approximately 80% are done this way) as this helps retain some varietal character, and gives better colour stability due to extraction of seed tannin during fermentation. Different portions of free run juice and the ‘flash water’ can also be added back into the ferment depending on the initial quality of the fruit and the quality and style of wine that is being targeted 28.
Result Thermo flash can make for very good, sound, solid wine, but at the expense of varietal character. Нigh heat can certainly volatize several categories of compounds: pyrazines to be sure, but also terpenes and thiols and in results wines are more intensely berryish but less complex, so it’s reduces varietal character. Pumping up the fruit and burning off the rough edges can have a downside in the loss of distinctiveness so it can only be used in small percentages 26.
Conclusions This isn’t a bad thing; technology that improves one component of a wine blend can be quite valuable, as in the contributions of a small proportion of barrelfermented white wine in a mostly tank-fermented cuvée. Flash-Détente system is a great way to add another layer to a wine, without being the universal option for all wines. But if it fills a number of niches—from removing pyrazines to enhancing purple tones, from denaturing enzymes to widening fermentation choices — it could earn its keep in custom-crush and large-production settings 26.
5. Other ways to reduce concentrations of MPs: � Juice clarification reportedly led to up to 50% reduction in IPMP concentrations after 24 h of settling 29, but juice clarification is not a viable option for red wine-making. � Thermo-vinification and juice heating are reported to reduce MPs, most likely by evaporative loss (50% estimated reduction after must heating 30), but this type of treatment leads to sensorial changes in the wines 31. � Fining wine with bentonite or activated charcoal was found to be non- (bentonite) to moderately (charcoal) effective and lacking selectivity. � Treatments based on the addition of oak chips resulted in no MP reduction but a masking effect was noted for the undesirable characteristics associated with elevated MP levels 32. � Light treatment and irradiation were also ineffective 33.
Selection of plastic polymers Plastic polymers are commonly used elsewhere in the food industry. These polymers can also cause “flavour scalping” – changes in the characteristics and the intensity of the food flavours/aromas from adsorption on the packaging material. While the capacity of polymers to “scalp” desirable odorants from packaged foods has been extensively researched 34 their efficacy at removing unwanted volatile compounds from foodstuff has only been reported in one study to date 35.
Methoxypyrazine concentrations and sensory characteristics of red wines treated with various plastic polymers 36 IPMP SBMP Treatmen (ng/l) Chang t ge (%) 17. 0 IBMP (ng/l) Chan ge (%) Overall MP Change (%) 21. 7 Descriptors Control wine 19. 7 Silicone tubing 13. 7 − 30. 5 15. 2 − 10. 4 11. 7 − 46. 2 − 30. 4 fruity, floral, nutty Biodegrad able 11. 8 − 37. 1 16. 8 − 0. 4 13. 2 − 39. 0 − 28. 3 a bit nutty, a bit medicinal LDPE 14. 3 − 27. 3 15. 4 − 9. 7 17. 7 − 18. 5 − 18. 9 nutty, chemical, EVA 13. 6 − 31. 1 16. 1 − 5. 4 18. 3 − 15. 5 − 17. 8 no faults, numbed nasal pyrazines, bell pepper, peanut s
Result Most polymers reduced the concentration of at least one MP; however, most also added unwanted aroma characteristics to the wines, such as rotten peanuts, chemical, pungent, or decaying vegetal. The three most successful polymers at decreasing overall MP levels were � EVA (18% overall reduction: 31% IPMP, 5% SBMP and 16% IBMP), �biodegradable polymer (28% overall reduction: 37% IBMP, 0. 4% SBMP and 46% IPMP) � silicone tubing (30% overall reduction: 31% IBMP, 10% SBMP and 46%IPMP). No negative descriptors were used in describing the wines treated with these three polymers 36.
For silicone, maximum reductions were achieved after 24 h for all three MPs (IPMP 96%, SBMP 71% and IBMP 100%). In the case of the biodegradable polymer, IPMP reduction was greatest after 24 h of polymer contact (52%); however, most of the effective IPMP removal occurs during the first 8 h of contact. IBMP registered the highest decrease after 24 h of contact (36%). For EVA, maximum reduction in IPMP was achieved after 24 h contact (7%), SBMP after 24 h (27%) and IBMP after 24 h contact (23%) 36.
Reduction of methoxypyrazines after silicone treatment as a function of contact time: (a) isopropyl methoxypyrazine (IPMP), (b) secbutyl methoxypyrazine (SBMP), (c) isobutyl methoxypyrazine 36
Conclusions If the suitability of plastic polymers as a treatment for reducing elevated MP levels in wine is confirmed, then these findings open the way for the use of these polymers on an industrial scale for treating MP-rich wines. Polymers are versatile and can be produced in a variety of forms, offering considerable flexibility from a practical stand point; they could be incorporated into filtration systems, used as tank inserts in sheet form or distributed as pellets in wines. They also offer a cost-effective and, in the case of the poly-lactic acid polymer, an environmentally friendly option for a currently very costly industry
References � 1 -Martin P. Mendez-Costabel “Factors affecting the levels of 3 - isobutyl-2 -methoxypyrazine and C 6 compounds in Vitis vinifera L. Merlot” 2012. � 2 -Aroma descriptors from literature(Buttery et al. 1969, Allen et al. 1989, Jakobsen et al. 1998, Lopez et al. 1999, Jorgensen et al. 2000, Lee et al. 2001, Cullere et al. 2004, Qian and Wang 2005, Klesk and Qian 2003, Genovese et al. 2007) � 3 -Fan, W. ; Xu, Y. ; Jiang, W. ; Li, J. Identification and quantification of impact aroma compounds in 4 nonfloral Vitis vinifera varieties grapes. J. Food Sci. 2010, 75, S 81–S 88 � 4 -J. Crouzet, C. Flanzy, Y. Z. Gunata, P. Pellerin, J. C. Sapis, in: C. Flanzy ¨ (Ed. ), Œnologie—Fondements Scientifiques et Technologiques, Part 10, Lavoisier Tec & Doc, Paris, 1998, p. 361 � 5 -Herraiz, T. ; Herraiz, M. ; Reglero, G. ; Martín-Álvarez, P. J. ; Cabezudo, M. D. Changes in the composition of alcohols and aldehydes of C 6 chain length during the alcoholic fermentation of grape must. J. Agric. Food Chem. 1990, 38, 969– 972. ). � 6 -Fang, Y. ; Qian, M. C. Development of C 6 and other volatile compounds in Pinot Noir grapes determined by Stir Bar Sorptive Extraction-GC-MS. � 7 -D. D. Ramey, A. Bertrand, C. S. Ough, V. L. Singleton, E. Sanders,
� 9 -Allen et al. , 1991; Murray and Withfield, 1975 � 10 -Belancic, A. ; Agosin, E. Methoxypyrazines in grapes and wines of Vitis � � � vinifera cv. Carmenere. Am. J. Enol. Vitic. 2007, 58, 462– 469 11 -Allen, M. S. ; Lacey, M. J. ; Harris, R. L. ; Brown, W. V. Contribution of methoxypyrazines to Sauvignon blanc wine aroma. Am. J. Enol. Vitic. 1991, 42, 109– 112 12 -Roujou de Boube, 2000 13 - Ryona et. al. , 2008 14 - Koch et al. , 2010 15 -Sala et al. , 2004; Belancic and Agosin, 2007 16 Gregan, S. M. ; Wargent, J. J. ; Liu, L. ; Shinkle, J. ; Hofmann, R. ; Winefield, C. ; Trought, M. ; Jordan, B. Effects of solar ultraviolet radiation and canopy manipulation on the biochemical composition of Sauvignon Blanc grapes. Aust. J. Grape Wine Res. 2012, 18, 227– 238 17 -Scheiner et al. , 2010 18 -Ryona et al. , 2008, Scheiner et al. , 2010; Suklje et al. , 2012 19 Deloire and Heyms, 2011 20 -Methoxypyrazines and greenness in wines: myth or reality? Nico Gobler, Zelmari Coetzee, Klemen Lisjak and Alain Deloire. 21 -Thomas Henick-Kling and Jim Harbertson “Late Ripening – How to Deal” 22 -Roujou de Boubee, D. , A. M. Cumsille, M. Pons, D. Dubourdieu. 2002. “Location of 2 -methoxy-3 -isobutylpyrazine in Cabernet Sauvignon grape bunches and its extractability during vinification. ” Amer. Jour. Enology & Viticulture. 53 (1): 1– 5
� 23 -Kay Bogart, Linda Bisson, Department of Enology &Viticulture. University of California, Davis «Persistence of vegetal characters in winegrapes and wine» MAR/APR 2006 � 24 -Roujou de Boubee, D. , A. M. Cumsille, M. Pons, D. Dubourdieu. 2002. “Location of 2 -methoxy-3 -isobutylpyrazine in Cabernet Sauvignon grape bunches and its extractability during vinification. ” Amer. Jour. Enology & Viticulture. 53 (1): 1– 5 � 25 - Suomalainen and Lehtonen 1979, Pretorius 2000, Orlic et al. 2007, Swiegers and Pretorius 2005 � 26 -Tim Patterso “ Inquiring Winemaker. Thermovinification Heats Up � � � � � Interest” Wines & Vines, December 2010 27 - «Flash Extraction Goes to Work» by Laurie Daniel January 2011 Issue of Wines & Vines 28 -Paul Baggio “Flash extraction – what can it do for you? ” 21. 10. 2015 29 -de Boubée et al. 2002; Kotseridis et al. 2008 30 -Kögel et al. 2012 31 -Jackson 2008 32 -Pickering et al. 2008 33 -Blake et al. 2010 34 -Ayhan et al. 2001; Van Willige et al. 2002; Berlinet et al. 2005; Licciardello et al. 2009 35 -Ryona et al. 2012 36 -“Application of plastic polymers in remediating wine with elevated alkylmethoxypyrazine levels” FOOD ADDITIVES AND CONTAMINANTS APRIL
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