Co-inoculation with Yeast and LAB Under Winery Conditions: Modification of the Aromatic Profile of Merlot Wines

The present work reports the impact of yeast/LAB co-inoculation on the aromatic profile of Merlot winesmade in wineries. This study was carried out over two consecutive years on five Merlot wines in Bordeauxand Swiss wineries, using Saccharomyces cerevisiae and Oenococcus oeni starter cultures. Seventy aromaticcompounds were quantified and, in addition, the sensory profiles of two wines were determined in orderto compare the aromatic notes of the sequential and co-inoculated wines. The influence of the timing ofinoculation with lactic acid bacteria (LAB) on the metabolic profile of wines was observed. It confirmedprevious work carried out on a micro-scale but, for the first time, the impact of yeast/LAB co-inoculationwas significantly demonstrated from a sensory point of view under winery conditions. In particular, thefruity and lactic notes, as well as the markers associated with these descriptors, such as esters and diacetyl,were altered. Co-inoculation does not always favour fruity expression, nor does it reduce the diacetylcontent and lactic aroma intensity. All of the trends were observed either in the production and degradationof metabolites, or by the development of an aromatic mask over the short and long term

Pre-fermentation approaches to producing lower alcohol wines from Cabernet Sauvignon and Shiraz: implications for wine quality based on chemical and sensory analysis

Pre-fermentative juice substitution with water or early harvest wine has the potential to produce lower alcohol wines without critically modifying colour or tannin properties and only marginally changing volatile and sensory profiles. Whether this approach is suited to producing lower alcohol wines in the absence of excessive grape ripeness remained to be determined. The current study extends on pre-fermentative approaches to alcohol management under milder grape ripening conditions and builds on an existing study with McLaren Vale Cabernet Sauvignon fruit, allowing for a direct comparison under two distinct vintage conditions. Given its importance to Australia, Shiraz was also included and underwent the same consecutive harvest and juice substitution treatments. Cultivar-dependent implications on wine chemical properties were apparent and declines in wine colour and tannin were particularly evident in Shiraz wines, although impacts on overall wine quality and sensory parameters were minor when adjusting musts within the limit of 13.5 °Baumé.Olaf J. Schelezki, Guillaume Antalick, Katja Šuklje, David W. Jeffer

Harvesting and blending options for lower alcohol wines: a sensory and chemical investigation

Background: Lower alcohol wines often have a poor reputation among consumers, in part due to their unsatisfactory flavours such as reduced overall aroma intensity or herbaceous characters. The aim of this study, performed on Verdelho and Petit Verdot, was to quantify the effectiveness of a monovarietal blend in which wines made from less ripe grapes were blended with an equivalent volume of a wine vinified from riper fruit to produce wines with a lower alcohol content and desirable ripe fruit flavours.Results: Eleven and 13 attributes, for Verdelho and Petit Verdot, respectively, were selected during sensory descriptive analysis. Intensities of perceived 'acidity', 'sweetness' and 'alcohol' attributes were significantly different (P ≤ 0.05) between the blend (8.8 ± 0.1% v/v) and mature Verdelho (10.3 ± 0.1% v/v) wines, while no significant differences were found between the Petit Verdot blend (11.0 ± 0.1% v/v) and mature (12.6 ± 0.2% v/v) treatments. Volatile composition of wines was assessed using HS-SPME-GC-MS. Partial least square regression suggested relationships between sensory descriptors and chemical attributes in the wines, as well as the modifications of sensory and compositional profiles following blending.Conclusions: The blending practice described allowed the production of wines with lower alcohol content while retaining similar sensory profiles of the later harvested, riper fruit wines

Two dimensional gas chromatography: a powerful tool to unravel wine volatiles

A temporal and spatial investigation of Shiraz wine volatile composition from four vineyards located in warm to hot climates in New South Wales Australia was conducted. Shiraz wines were made from grapes harvested at two different berry maturity levels based upon a sugar accumulation model. Grape harvests were conducted between 10 to 12 days apart (H1 and H2, respectively) and wines made in triplicate using controlled fermentations. Wine volatile compounds were analysed by head space-solid phase micro extraction coupled to comprehensive two dimensional gas chromatography quadrupole time of flight mass spectrometry (HS-SPME-GCxGC-TOFMS). Acquired data were deconvoluted and aligned with LECO ChromaTOF Version 4.22 software at a signal to noise ratio 100. A total of 1240 putative compounds were detected, of which 240 were significantly different in at least one of the harvest dates among four vineyards. Compound identity was confirmed by authentic standards, Kovats retention index and or by comparing spectra of compounds to the NIST 2.0, Wiley 8 and the FFNSC 2 (Chromaleont, Messina, Italy) mass spectral libraries. A clear separation of samples based on the harvest date is evident in Principal Component 1 which accounted for 40% of data variation. Derivates of lipoxygenase pathway, i.e. C5, C6 and C9 compounds were typically found in higher levels in wines from the first harvest (H1) compared to wines from the second harvest (H2), irrespective of vineyard site. However, this trend was less pronounced for C6 esters such as E-hexenyl acetate and Z-3-hexenyl acetate. Several monoterpenes, norisoprenoids and sesquiterpenes were also identified in wines, however no clear trend according to harvest date is evident for these compounds. Preliminary results indicate significant and coherent modulations of wine volatiles in relation to harvest date, irrespective of vineyard location with similar climatic parameters. HS-SPME GCxGC-TOFMS was proven to be fast, reliable and a powerful technique to unravel wine volatile composition

Volatile and sensory profiling of Shiraz wine in response to alcohol management: comparison of harvest timing versus technological approaches

The aim of this study was to compare the volatile and sensory profiles of Australian Shiraz red wines produced by several methods to achieve alcohol concentrations of 10.5 and 13.5% v/v. These levels were considerably lower contents than the commercial wine (16-17% v/v) that was produced from this vineyard site. Wines were produced by: (i) harvest timing (19.3, 24 and 29.3 Brix); (ii) blending equal proportions of early harvest (19.3 Brix) and late harvest wines (29.3 Brix); and (iii) dealcoholization using reverse osmosis followed by a membrane contactor. Dealcoholization caused a significant loss of volatile compounds, particularly esters, while the blending treatment had an averaging effect on most analytes. Sensory descriptive analysis of treatments with 10.5% v/v alcohol showed that the perception of the herbaceous attribute was more intense in the early harvest wines in comparison to the dealcoholized wines, while those of dark fruit, raisin/prune, astringency and alcohol were lower. No sensory differences were found amongst the 13.5% v/v wines, except for alcohol. Sensory and compositional data were modelled by means of Common Dimension (ComDim) multi-block analysis and indicated which chemical components are important to the perceived wine sensory properties. Insights from this study will provide knowledge that may be applied to control or moderate both unripe sensory attributes in addition to a deficiency of ripe fruit aromas or mouthfeel characteristics in reduced-alcohol red wines

Cultivar, site or harvest date: the gordian knot of wine terroir

Introduction The complex interactions of vine cultivars, and localised regional climate associated with specific vineyard sites are important attributes to the concept of terroir and significant contributors to grape maturity and wine sensory profiles. An improved understanding of the influence of each factor and their interactions is a challenging conundrum, and will enable more efficient production targeting specific wine styles. Objectives To characterise the metabolic flux of grape berries and resulting wines to characterise the relative impact of site specific climate, cultivar, and grape maturity based upon berry sugar accumulation models that consistently target specific wine styles. Methods A spatial and temporal study of grape and wine composition was undertaken for two important cultivars in two distinct regions of New South Wales. Measures of composition and wine sensory ratings were simultaneously analysed using a multiblock algorithm taking advantage of the ANOVA framework to identify important contributions to wine style arising from grape maturity, vineyard site and cultivar. Results A consistent flux of grape and wine constituents is evident for wine made from sequentially harvested grapes from the same vineyard with increasing levels of grape maturity. Contributions of region and vineyard site to wine style could also be elucidated. Differences in metabolite flux in grapes and resulting wines between cultivars growing in similar conditions are evident. Conclusions The combination of a metabolomics and multiblock data decomposition approach may be successfully used to profile and elucidate the contribution of abiotic factors to grape and wine composition and provide improved understanding of the terroir concept

Unravelling the effect of harvest date on Shiraz wine volatile composition by two dimensional gas chromatography and wine sensory analyses

An investigation of Shiraz wine volatile composition from four vineyards located in the Riverina region of Australia was performed by accessing wines made from sequentially harvested grapes. Vines were drip irrigated with average yields from 10.2-18.5 kg/vine in the four vineyards. Shiraz wines were vinified from 60 kg grape triplicates. Following a berry ripening model [1], the first harvest (H1) was 12 days from the plateau of berry sugar accumulation and the second harvest (H2), 24 days after the plateau. Data acquired by HS-SPME-GC×GC-TOFMS were deconvoluted and aligned with LECO ChromaTOF Version 4.22 software at a signal to noise ratio of 100. A total of 1240 putative compounds were detected by HS-SPME-GC×GC-TOFMS in at least one of the samples. A comparison of vineyards revealed that approximately 200 of compounds were found to be at significantly different levels in at least one of the harvest dates. Principal component analyses illustrated a separation of samples based on harvest date. C5, C6 and C9 compounds, known as green leaf volatiles, were typically found in higher levels in H1 wines. Modifications of yeast metabolism of the sulfur-containing amino acid, methionine, were noticed. Methionol, methional and ethyl 3-(methylthio)-propionate were significantly lower in H2 wines whereas 2-(methylthio)-ethanol was increased. Several higher alcohol acetates were also measured at higher levels in H2 wines. Sensory evaluation revealed significant differences in wines based on the harvest date determined by berry ripening model. Wines from grapes harvested at H1 were perceived by panellists to be higher in red fruit attributes whereas wines from H2 were perceived higher in dark fruit and plum characters. These results indicate significant modulation of wine volatiles as a consequence of harvest dates, by altering lipoxygenase derived compounds and yeast metabolism, irrespective of vineyard cultural practices, within the same warm to hot climatic region

Unravelling wine volatile evolution during shiraz grape ripening by untargeted hs-spme-GC×GC-tofms

The influence of grape maturity on wine volatome was investigated using HS-SPME-GC×GC-TOFMS. Shiraz wines were made from grapes harvested from four different vineyards from two berry maturity levels. A total of 1,276 putative compounds were detected in at least one of the wine samples and 175 showed significant trends related to grape maturity. The first two dimensions of the Principal component analysis accounted for 57% of the variation and separated the samples according to the harvest date. Wines from the first harvest date were characterised by an abundance of lipoxygenase derived compounds, norisoprenoids and sulfur-containing compounds whereas a significant increase in some acetate esters was observed in wines produced from the more mature grapes. This study demonstrated a common evolution of grape volatiles for Shiraz inside the same mesoclimate. During the late ripening stage of the grape, a direct nexus between sugar concentration and wine volatile evolution was not observed