JULY/AUGUST 2002 WINEGROWING Understanding grape berry development

BY James Kennedy, Department of There is a potential for tremendous would be uniformly ripe clusters with Food Science & Technology variability in ripening between berries small berries chock-a-block with flavor. Oregon State University, Corvallis, OR within a grape cluster, and therefore An understanding of berry anatomy, within the vineyard.18,19,20 Practically when and where berry components are n the world of winemaking, there speaking, it is difficult to determine produced, is the first step in under- is a universal truth about the qual- when a vineyard with a large varia- standing the rationale behind manag- ity of the vintage: It is directly cor- tion in berry maturity is at its best pos- ing wine style in the vineyard. related with optimal grape matu- sible ripeness. One of the major objec- Irity. Site selection and grapegrowing Berry structure practices have a From a wine- tremendous influ- making perspec- ence on achieving tive, the grape optimal maturity. berry has three A considerable major types of tis- amount of viticul- sue (Figure I): tural research has flesh, skin, and identified strate- seed, with the gies that can be sheer bulk of wine used to optimize being derived from grape maturity at the flesh. These harvest including tissues vary con- irrigation,1,2,3 canopy siderably in com- management,4–9 and position, and cropping lev- therefore by exten- els,10,11,12 among oth- sion, they con- ers.13–16 To fully ap- tribute differently to preciate how these overall wine com- strategies can be position. Because used to optimize of this, the compo- grape maturity, sition of wine can grapegrowers and be manipulated winemakers should by simply chang- have an under- ing berry size. As standing of berry a general rule, development. wines made from smaller berries will Fruit have a higher pro- development portion of skin and The grape berry is seed derived com- essentially an inde- pounds. pendent biochemi- In addition to 17 cal factory. Be- Figure I: Structure of a ripe grape berry partially sectioned on the long and central axis to the effect of berry yond the primary show internal parts. Illustration by Jordan Koutroumanidis, Winetitles. size on the propor- metabolites essential tion of skin and for plant survival (water, sugar, amino acids, tives of modern viticulture is to be seed-derived components in wine, the minerals, and micronutrients), the berry has able to produce a uniformly ripe crop. actual number of seeds in the berry can the ability to synthesize all other berry com- If premium winemakers were to influence the proportion of seed-derived ponents (for example, flavor and aroma come up with what constituted the components in wine. The normal or per- compounds) that define a particular wine. ideal, optimally ripe vineyard, it fect number of seeds in the grape is four; 21 2 JULY/AUGUST 2002 WINEGROWING

in general though, the actual number is that xylem is functional in grape accompanied by increases in berry vol- much less. berries early in development (up to ume, but are caused by berry shrink- Environmental and nutritional con- véraison), but afterward, its function is age. This shrinkage appears to be due ditions at bloom time affect the success reduced or eliminated.25 to the transiprational loss of water,26,27,28 of fertilization, and the resulting The berry is also supplied by the suggesting that the inability of the number of seeds per berry,20,22,23,24 and phloem, which is the vasculature berry to stay well-hydrated at this therefore can be expected to influence involved in photosynthate (sucrose) point is due to blockage of phloem ele- the presence of seed-derived material transport from the canopy to the vine. ments into the berry. This indicates in wine. It has reduced function early in berry that, for some varieties, the vasulature The berry is supplied through the development, but becomes the pri- between the vine and the berries has berry stem or pedicel by a vascular sys- mary source of ingress after véraison.25 reduced function during late season tem composed of xylem and phloem Increases in berry volume (primar- fruit ripening. elements. The xylem is the vasculature ily water) are associated with increases responsible for transporting water, in sugar after véraison. However, in Development during minerals, growth regulators, and nutri- some grape varieties (most notably first growth period ents from the root system to the rest of Syrah), sugar increases during the lat- Berry development consists of two the vine. Current evidence indicates ter stages of fruit ripening are not successive sigmoidal growth periods sep-

Xylem flow ceases Phloem

Xylem Engustment

Veraison lag phase Berry Size Periods when compounds accumulate

Tartrate Tannin Hydroxycinnamates Methoxypyrazine Malate Glucose Fructose Anthocyanin Flavour compounds pericarp cell division

setting

0 20 40 60 80 100 120

Flowering Days after flowering ºBrix4 7 10 14 18 22 26

BERRY FORMATION BERRY RIPENING

Figure 2: Diagram showing relative size and color of berries at 10-day intervals after flowering, passing through major developmental events (rounded boxes). Also shown are the periods when compounds accumulate, the levels of juice obrix, and an indication of the rate of inflow of xylem and phloem vascular saps into the berry. Illustration by Jordan Koutroumanidis, Winetitles. JULY/AUGUST 2002 3 WINEGROWING

arated by a lag phase (Figure II).18 The first standing berry formation and the fac- Notable aroma compounds that are period of growth lasts from bloom to tors that affect its formation is still lim- produced during the first period of approximately 60 days afterward. During ited because of the complex nature of growth, decline (again, on a per-berry the first growth period, the berry is this type of research. basis) during fruit ripening. These formed and the seed embryos are pro- Understanding berry development include several of the methoxypyrazine duced. Rapid cell division occurs through and its compositional changes during the compounds that contribute vegetal char- the first few weeks, and by the end of this first growth period is limited probably acters to some wines (such as Cabernet period, the total number of cells within because the compounds produced are Sauvignon and Sauvignon Blanc).39 The the berry has been established.29 The thought to be of less interest from a sen- decline in pyrazines is thought to be extent of cell division has some bearing on sory standpoint. It should be remembered linked to sunlight levels in the cluster. the eventual size of the berry. though, all compounds discussed above Therefore, if these compounds are Also during the first growth period, are critically important to wine quality. deemed to be undesirable (the current the berry expands in volume as solutes prevailing opinion), then canopy man- accumulate. There are several solutes Development during agement can be used to reduce them. that accumulate in the berry during the second growth period Despite these major changes in com- first growth period, all of which reach The beginning of the second phase of pounds produced during the first an apparent maximum around vérai- berry growth or fruit ripening (véraison) growth period, the big story during the son.30 By far the most prevalent among is characterized by softening and color- second growth period is the tremen- these are tartaric and malic acid. ing of the berry. Overall, the berry dous increase in compounds (the major These acids are distributed in the approximately doubles in size between ones being glucose and fructose) that berry somewhat differently, with tar- the beginning of the second growth occurs as a result of a total biochemical taric acid being highest towards the period and harvest. Many of the solutes shift into fruit ripening mode. outside of the developing berry, and that accumulated in the grape berry dur- Beginning at véraison, sugar influx malic acid being highest in the flesh. ing the first period of development into the berry commences. Sucrose pro- Tartaric acid appears to accumulate remain at harvest, yet due to the increase duced from photosynthesis is imported during the initial stages of berry devel- in berry volume, their concentration is into the grape berry during fruit ripen- opment, and malic acid accumulates reduced significantly. ing. Once transported into the berries, just prior to véraison. These acids pro- Some compounds produced during the sucrose is hydrolyzed into its con- vide wine with acidity and are there- the first period of growth are reduced stituent sugars glucose and fructose.40 fore critical to wine quality. on a per-berry basis (not simply Their eventual concentration is dictated Also accumulating during the initial diluted) during the second period of partly by the length of time the grape period of growth are the hydroxycinnamic berry growth. Principal among these is berry is allowed to stay on the vine. acids.31 Hydroxycinnamic acids are dis- malic acid. Its reduction varies consid- (Other factors include the crop load, tributed in the flesh and skin of the berry erably but can roughly be correlated canopy size, disease status, and as men- and are important because of their with climate. That is, grapes grown in tioned earlier, dehydration). involvement in browning reactions, and warmer regions tend to have less malic Beyond sugar accumulation, the because they are precursors to volatile acid than those grown in cooler regions major determinants of a wine’s quality phenols.32 as a result of this reduction. are the secondary metabolites. In red Tannins including the monomeric Tannins also decline considerably grape varieties, anthocyanin production catechins also accumulate during the on a per-berry basis during the second (restricted to skin tissue in most culti- first period of growth.33,34 Tannins are period of growth. The reduction in vars) is probably the most obvious com- present in skin and seed tissues and seed tannin appears to be due to oxida- pound of importance, but as with white nearly absent in the flesh, and are tion as the tannins become fixed to the varieties, most of the volatile flavor com- responsible for the bitter and astrin- seed coat.38 As a result of this, the com- ponents are produced during fruit ripen- gent properties of red wine. These position of extracted seed tannins ing.41–45 These would include such com- compounds are also believed to be changes considerably, and is character- pound classes such as terpeneoids, important in red wine color stability. ized by a proportional reduction in the which are important to the pleasant There are other compounds that most bitter tannin components. aroma of many varieties, such as Riesling accumulate in the berry during the Skin tannins decline or remain con- and Muscat, and fruity aroma precur- first phase of growth, and which have stant during the second period of sors. Aroma compounds are distributed importance to wine quality. growth, and also become modified. in the flesh and skin of the berry. Minerals,30 amino acids,35 micronutri- Significant modifications that take In addition, many other important ents, and aroma compounds (such as place for the skin tannins include an aroma and flavor compounds are pro- methoxypyrazines36,37) have all been increase in their size. Also of potential duced late in fruit ripening. Some of observed during the first period of significance from a wine quality stand- these components are produced as berry growth. point is evidence that extracted skin precursors, and are not actually Our understanding of berry forma- tannins are modified with pectins and volatile until after the wine has been tion and development during the first anthocyanins.33 This could make berry produced and aged for some time.46 period of growth and of the production development an important considera- Nevertheless, their precursors are pre- of compounds having sensory impor- tion in the areas of wine texture and sent in the grape as glycosides, and the tance is still developing. Under- color stability. period of time where many of them 4 JULY/AUGUST 2002 WINEGROWING

appear to be produced has recently been in particular stages of development,” Amer. 15. Marais, J., van Wyk, C. J., Rapp, A. given the term “gustation.”47 Jour. of Enology & Viticulture 27: 55-61. (1991) “Carotenoid levels in maturing In examining berry development, it 3. Matthews, M. A., Anderson, M. M. (1987) grapes as affected by climatic regions, sun- helps to look at it from an ecological “Reproductive development in grape (Vitis light and shade,” South African Journal of perspective. If the raison d’être for the vinifera L.), responses to seasonal water deficits,” Enology & Viticulture 12: 64-69. berry is to reproduce, then its first pri- Amer. Jour. of Enology & Viticulture 40: 52-60. 16. Reynolds, A. G., Wardle, D. A. (1997) “Flavour development in the vineyard: ority is to develop a viable seed. 4. Crippen, D. D., Morrison, J. C. (1986) “The effects of sun exposure on the pheno- impact of viticultural practices on grape During the first period of growth the lic content of Cabernet Sauvignon berries monoterpenes and their relationship to berry does just that. It develops a during development,” Amer. Jour. of Enology wine sensory response,” South African viable seed and produces compounds & Viticulture 37: 243-246. Journal of Enology and Viticulture 18: 3-18. to protect it while doing so. 5. Dokoozlian, N. K., W.M. Kliewer 17. Gholami, M., Hayasaka, Y., Coombe, If you think about the compounds (1996) “Influence of light on grape berry B. G., Jackson, J. F., Robinson, S.P. Williams, P.J. that are produced during the first period growth and development varies during (1995) “Biosynthesis of flavour compounds in of growth (organic acids, tannins, fruit development,” Jour. of the Amer. Society Muscat Gordo Blanco grape berries,” Australian pyrazines), they combine to make forag- of Horticultural Science 121: 869-874. Journal of Grape & Wine Research 1: 19-24. ing by birds and mammals a downright 6. Hunter, J. J., Visser, J. H. (1990) “The 18. Coombe, B. G., McCarthy, M.G. unpleasant experience. By the end of the effect of partial defoliation on growth (2000) “Dynamics of grape berry growth first period of growth, a viable seed has characteristics of Vitis vinifera L. cv. Cabernet and physiology of ripening,” Australian been produced, and therefore, the goal Sauvignon II. Reproductive growth,” South Journal of Grape & Wine Research 6: 131-135. 19. Coombe, B. G. (1987) “Distribution during the second period of berry African Jour. of Enology & Viticulture 11: 26-32. of solutes within the developing grape growth is to make the berry as appealing 7. Hunter, J. J., Ruffner, H. P., Volschenk, C. G., Le Roux, D. J. (1995) “Partial defolia- berry in relation to its morphology,” Amer. as possible to birds and mammals so that Jour. of Enology & Viticulture 38: 120-127. seed dispersal can occur. tion of Vitis vinifera L. cv. Cabernet Sauvignon/99 Richter: effect on root 20. Coombe, B. G. (1973) “The regula- growth, canopy efficiency, grape composi- tion of set and development of the grape Conclusion tion, and wine quality,” Amer. Jour. of berry,” Acta Horticulturae 34: 261-273. Many advances have been made in Enology & Viticulture 46: 306-314. 21. Bioletti, F. (1938) “Outline of ampel- understanding of how the grape berry 8. Rojas-Lara, B. A., Morrison, J. C. ography for the Vinifera grapes in develops and of the components that are (1989) “Differential effects of shading fruit California,” Hilgardia 11: 227-293. important in wine. No doubt the quality or foliage on the development and compo- 22. Ebadi, A., Coombe, B. G., May, P. of our wines has improved as a direct sition of grape berries,” Vitis 28: 199-208. (1995) “Fruit-set on small Chardonnay and result of being able to manipulate the 9. Smart, R. E. (1980) “Vine manipula- Shiraz vines grown under varying temper- grape berry through production practices. tion to improve wine grape quality,” ature regimes between budburst and flow- ering,” Australian Jour. of Grape & Wine Understanding when various compo- University of California, Davis Grape and Wine Centenial Symposium Proceedings 362-375. Research 1: 3-10. nents accumulate in the berry is critically 23. Ebadi, A., May, P., Sedgley, M., important to understanding how grape- 10. Eschenbruch, R., Smart, R. E., Fisher, B. M., Whittles, J. G. (1986) “Influence of Coombe, B. G. (1995) “Effect of low temper- growing practices can be used to modify yield manipulations on the terpene content ature near flowering time on ovule devel- wine style. It is clear that this is an area of of juices and wines of Müller Thurgau,” opment and poleen tube growth in the research that will continue in the future, Proceedings of the 7th Australian Wine grapevine (Vitis vinifera L.), cvs yet it is already apparent that a wine- Industry Technical Conference 89-93. Chardonnay and Shiraz,” Australian Jour. of maker can influence wine style through 11. Kliewer, W.M., Dokoozlian, N. K. Grape & Wine Research 1: 11-18. grapegrowing practices. The trick is (2000) “Leaf area/crop weight ratios of 24. Ewart, A., Kliewer, W.M. (1977) understanding the what, when, and how grapevines: influence on fruit composition ”Effects of controlled day and night tem- of berry manipulation. ■ and wine quality,” Proceedings of the Amer. peratures and nitrogen on fruit-set, ovule Society for Enology & Viticulture 50th fertility, and fruit composition of several wine grape cultivars,” Amer. Jour. of Enology Illustrations provided by Australian Anniversary Annual Meeting 285-295. 12. Intrieri, C., Filippetti, I. (2000) & Viticulture 28: 88-95. Viticulture from text: “Ripening berries — “Planting density and physiological bal- 25. Greenspan, M. D., Shackel, K. A., a critical issue” by Dr. Bryan Coombe, ance: comparing approaches to European Matthews, M. A. (1994) “Developmental (Honorary Visiting Research Fellow, viticulture in the 21st century,” Proceedings changes in the diurnal water budget of the Adelaide University, Australia) and Tony of the Amer. Society for Enology & Viticulture grape berry exposed to water deficits,” Clancy (Editor, Australian Viticulture), 50th Anniversary Annual Meeting 296-308. Plant Cell & Environment 17: 811-820. March/April 2001. Illustrations prepared 13. Jackson, D. I., P.B. Lombard (1993) 26. McCarthy, M.G. (1997) “The effect of transient water deficit on berry develop- by Jordan Koutroumanidis. “Environmental and management practices affecting grape composition and wine qual- ment of cv. Shiraz (Vitis vinifera L.),” ity—a review quality,” Amer. Jour. of Enology Australian Journal of Grape & Wine Research References & Viticulture 44: 409-430. 3(3): 102-108. 1. Bravdo, B., Hepner, Y. (1986) “Water 14. Marais, J., van Wyk, C. J. (1986) 27. McCarthy, M.G. (1999) “Weight loss management and the effect on fruit quality in “Effect of grape maturity and juice treat- from ripening grapevines (Vitis vinifera L. grapevines,” Proceedings of the 6th Australian ments on terpene concentrations and wine cv. Shiraz),” Australian Journal of Grape & Wine Industry Technical Conference 150-158. quality of Vitis vinfera L. cv. Weisser Riesling Wine Research 5(1): 10-16. 2. Hardie, W.J., Considine, J. A. (1976) and Bukettraube,” South African Jour. of 28. McCarthy, M.G., Coombe B. G. “Response of grapes to water-deficit stress Enology & Viticulture 7: 26-35. (1999) “Is weight loss in ripening grape JULY/AUGUST 2002 5 WINEGROWING

berries cv. Shiraz caused by impeded 35. Stines, A. P., Grubb, J., Gockowiak, volatile monoterpene flavorants of grapes,” phloem transport?” Australian Journal of H., Henschke, P.A., Høj, P.B., van Amer. Jour. of Enology & Viticulture 35: 66-71. Grape & Wine Research 5: 17-21. Heeswijck, R. (2000) “Proline and arginine 42. Marais, J. (1983) “Terpenes in the 29. Harris, J. M., Kriedemann, P.E., accumulation in developing berries of Vitis aroma of grapes: a review,” South African Possingham, J.V. (1968) “Anatomical aspects vinifera L. in Australian vineyards: influence Jour. of Enology & Viticulture 4: 49-60. of grape berry development,” Vitis 7: 106-109. of vine cultivar, berry maturity and tissue 43. Marais, J. (1994) “Sauvignon blanc 30. Possner, D. R. E., Kliewer, W.M. type,” Australian Jour. of Grape & Wine cultivar aroma — a review,” South African (1985) “The localization of acids, sugars, Research 6:150-158. Jour. of Enology & Viticulture 15: 41-45. potassium and calcium in developing grape 36. Allen, M. S., Lacey, M.J., Brown, W.V., 44. Park, S. K., Morrison, J. C., Adams, berries,” Vitis 24: 229-240. Harris, R. L. N. (1989) “Contribution of D. O., Noble, A. C. (1991) “Distribution of 31. Romeyer, F.M., Macheix, J. J., Goiffon, methoxypyrazines to the flavour of Cabernet free and glycosidically bound monoter- J. P., Reminiac, C.C., Sapis, J. C. (1983) “The Sauvignon and Sauvignon blanc grapes and penes in the skin and mesocarp of Muscat browning capacity of grapes. 3. Changes and wines,” Proceedings of the 7th Australian Wine of Alexandria grapes during develop- importance of hydroxycinnamic acid-tartaric Industry Technical Conference 113-116. ment,” Jour. of Agricultural & Food acid esters during development and matura- 37. Allen, M. S., Lacey, M.J. (1999) Chemistry 39: 514-518. tion of the fruit,” Jour. of Agricultural & Food “Methoxypyrazines of grapes and wines,” Chemistry 31: 346-349. In: Chemistry of Wine Flavor A. L. Water- 45. Wilson, B., Strauss, C. R., Williams, 32. Licker, J. L., Acree, T. E., Henick-Kling, house and S.E. Ebeler Eds. American P. J. (1984) “Changes in free and glycosidi- T. (1999) “What is ‘Brett’ (Brettanomyces) fla- Chemical Society Washington, DC 31-38. cally bound monoterpenes in developing vor? A preliminary investigation,” In: 38. Kennedy, J.A., Matthews, M. A., Muscat grapes,” Jour. of Agricultural & Chemistry of Wine Flavor A. L. Waterhouse and Waterhouse, A. L. (2000) “Changes in grape Food Chemistry 32: 919-924. S. E. Ebeler Eds. American Chemical Society seed polyphenols during fruit ripening.” 46. Francis, I. L., Kassara, S., Noble, Washington, DC 96-115. Phytochemistry 55: 77-85. A. C., Williams, P.J. (1999) “The contribu- 33. Kennedy, J.A., Hayasaka, Y., Vidal, S., 39. Hashizume, K., Samuta, T. (1999) tion of glycoside precursors to Cabernet Waters, E. J., Jones, G. P. (2001) “Composition “Grape maturity and light exposure affect Sauvignon and Merlot aroma,” In: of Grape Skin Proanthocyanidins at Different berry methoxypyrazine concentration quality,” Chemistry of Wine Flavor A.L. Waterhouse Stages of Berry Development.” Jour. of Amer. Jour. of Enology & Viticulture 50: 194-198. and S. E. Ebeler Eds. American Chemical Agricultural & Food Chemistry 49: 5348-5355. 40. Robinson, S. P., Davies, C. (2000) Society Washington, DC 13-30. 34. Kennedy, J.A., Troup, G. J., Pilbrow, “Molecular biology of grape berry ripen- 47. Coombe, B. G., McCarthy, M.G. J. R., Hutton, D. R., Hewitt, D., Hunter, C. A., ing.” Australian Jour. of Grape & Wine Ristic, R., Iland, P.G., Jones, G. P. (2000) Research 6(2):168-174. (1997) “Identification and naming of the “Development of seed polyphenols in berries 41. Dimitriadis, E., Williams, P.J. (1984) inception of aroma development in ripen- from Vitis vinifera L. cv. Shiraz.” Australian “The development and use of a rapid analytical ing grape berries,” Australian Jour. of Grape Jour. of Grape & Wine Research 6: 244-254. technique for estimation of free and potentially & Wine Research 3: 18-20.

Reprinted from:

58 Paul Drive, Ste. D, San Rafael, CA 94903 • 415-479-5819

Visit our website: www.practicalwinery.com to learn more about PWV.