Integrative Effects of Vine Water Relations and Grape Ripeness Level of Vitis vinifera L. cv. Shiraz/Richter 99. II. Grape Composition and Wine Quality

Abstract

Regulation of grapevine water status is a common practice to manipulate grape composition and wine quality. In this investigation the effect of plant water status (two field water capacity-based irrigation levels, 75% and 100%, applied at single and combined vine developmental stages) and ripeness level (harvesting at different soluble solid levels) on grape composition and wine quality of Vitis vinifera L. cv. Shiraz/ Richter 99 was determined. Integrative effects of vine water relations and grape ripeness level, specifically in a Mediterranean high winter rainfall area, have not yet been investigated systematically. Source:sink mechanisms and dynamics and compositional and physical changes during both green berry and ripening periods (and in response to environment changes), seemed critical for the final grape composition and wine quality/style. Despite relatively favourable conditions of the experiment terroir, additional water was still required to obtain best grape and wine quality. Skin colour and total phenolic contents were stimulated in particular by 75% (field water capacity) pea size (PS) irrigation, post-véraison (PV) irrigation and 75% pea size+post-véraison irrigation, until the last harvest stage. Treatments that included post-véraison irrigation were not negative in terms of ripening parameters. Increasing total soluble solids with ripening were not followed in parallel by anthocyanin potential. Anthocyanin extractability increased with ripening. A late, overripe harvest may result in wines that are slightly better coloured, but highly alcoholic and tannic. Furthermore, at high ripeness level, differences between treatments largely diminished. Over-ripeness of grapes may have tempering and even negative effects on expected outcomes of seasonal cultivation efforts to produce unique wines. This would not favour economic viability. Although non-irrigated wines failed to result in exceptional wine quality at any harvest stage, a better result in overall quality was obtained in comparison to irrigation treatments applied at all stages. Berry and wine composition results corresponded with findings on wine sensorial quality. The 75% PS, PV irrigation, and 75% PS+PV irrigation consistently resulted in good quality wines. At the first harvest stage, 75% PV, 100% PV, 75% PS+V and 75% PS+PV irrigations gave most prominent wines; at the second harvest stage, vines irrigated 75% at PS, 75% at PS+PV and 75% at PV delivered most prominent wines; and at the third harvest stage, 75% PV, 100% PV, 75% PS and 75% PS+PV resulted in most prominent wines. These treatments represented different wine styles at each harvest stage. Restricted PS irrigation and PV irrigation, as single or combined treatments, featured prominently in favouring grape and wine composition and wine sensorial quality. Physical and compositional changes in ripening berries and the impact on wine quality and style were further clarified. New perspectives on managing time of harvesting with varying vine water status are given. Recommendations on vi...

Chemical composition and sensory properties of non‐wooded and wooded Shiraz (Vitis vinifera L.) wine as affected by vineyard row orientation and grape ripeness level

“…Although the latter trend is in relation to soluble solid contents as well as titratable acidity and pH values, it is clear that anthocyanin and phenolic contents were not positively related to soluble solid contents. This is in agreement with results found in a study on Shiraz/Richter 99 in the Stellenbosch region in which various water levels were implemented by means of combinations of irrigation volumes and phenological stages; 46 skin anthocyanin and phenolic contents indicated almost complete development approximately 3 weeks after veraison. Results also correspond to those found in other studies 6,11,8,47 but are in contrast to those reported by Keller and Hrazdina 48 and Esteban et al 49 According to Fournand et al, 11 findings may suggest a change from free anthocyanins to derivatised anthocyanins with an increase in ripeness level.…”

“…According to Fournand et al, findings may suggest a change from free anthocyanins to derivatised anthocyanins with an increase in ripeness level. The decreasing trend in flavonoid contents with ripening paralleled a loss of water from berry skins, conforming to a reduction in berry volume and the study of Hunter et al . in which the decrease in anthocyanin content was associated with a loss of berry skin water.…”

“…Results also correspond to those found in other studies 6,11,8,47 but are in contrast to those reported by Keller and Hrazdina 48 and Esteban et al 49 According to Fournand et al, 11 findings may suggest a change from free anthocyanins to derivatised anthocyanins with an increase in ripeness level. The decreasing trend in flavonoid contents with ripening paralleled a loss of water from berry skins, conforming to a reduction in berry volume 10 and the study of Hunter et al 46 in which the decrease in anthocyanin content was associated with a loss of berry skin water. In a study on grapes from the same vineyard of this study, a significant decrease in berry skin strength, as evaluated by the berry skin break force mechanical parameter, was also found between consecutive ripeness levels; this was further enhanced during berry maceration and wine fermentation processes.…”

“…50 Despite the anthocyanin contents being similar, the consistently higher berry mass and volume 10 of the EW orientation compared with those of the other row orientations may have led to a lower extraction potential of flavonoids during crushing and alcoholic fermentation at all ripeness levels. 6,8,14,51,52 A loss in cellular integrity during the berry softening and shrinking process during ripening, a phenomenon commonly associated with the Shiraz cultivar, 46,50,[53][54][55][56][57][58] may enhance extraction from skins during vinification, but sun exposure, berry size (affecting the skin/pulp ratio) and heating of berries have all been associated with either reduction or enhancement of anthocyanin content of berries. [59][60][61] Surface/volume ratios cannot always be considered a measure of level of extractable quality-determining compounds.…”

“…78,79 Although wines made at higher grape ripeness levels received generally higher scores from judges, grapes should only be allowed to ripen to higher ripeness levels under uniform growth conditions, judicious management and favourable climatic conditions in order to maintain control over must chemical development and balances as well as to prevent tempering of expected outcomes and economic viability/sustainability. 46,58 The canopy and management thereof thus have a critical and increasingly important role as berry development and ripening proceed during the season to support balanced grape composition, to further formation of primary and secondary compounds contributing to taste and structure of wine and to prevent flavour and colour loss by over-exposure and over-ripeness. Berry sunlight exposure and temperature are well-known regulating drivers of biochemical and physiological processes during berry development and ripening that determine oenological quality.…”