Harvest date effects on aroma compounds in aged Riesling icewines.

BACKGROUND: Riesling icewine is an important product of the Ontario wine industry. The objective of this study was to characterize concentrations in aroma compounds in aged icewines associated with three harvest dates (H1, H2, H3) using stir bar sorptive extraction-gas chromatography-mass spectrometry and to make inferences, where appropriate, with respect to their roles in potential wine quality. RESULTS: Delaying harvest decreased concentrations of many odorants, but increased many critical odor-active compounds; e.g. 1-octen-3-ol, ethyl benzoate, ethyl octanoate, cis-rose oxide, and ß-ionone. H1 wines had higher concentrations of four aldehydes, three alcohols, nine esters, seven terpenes, γ-nonalactone, p-vinylguaiacol, ß-damascenone, and 2-furanmethanol. However, many of these compounds, with some exceptions, have relatively high odor thresholds. Fourteen compounds were above their odor thresholds, including decanal, 1-octen-3-ol, phenylethyl alcohol, four ethyl esters, cis-rose oxide, linalool, γ-nonalactone, p-vinylguaiacol, ethyl cinnamate, ß-damascenone, and 1,1,6-trimethyl-1,2-dihydronaphthalene. H3 wines contained higher concentrations of highly odor-active compounds, e.g. 1-octen-3-ol, cis-rose oxide, and ß-ionone. Only phenylethyl alcohol [H3 odor activity value (OAV) = 0.33 (honey, spice, rose)] and linalool [H3 OAV = 0.92 (floral, lavender)] had H3 OAVs < 1. CONCLUSIONS: Early harvest increased many esters and aliphatic compounds, but delayed harvest appeared to substantially increase concentrations of several highly odor-active compounds. © 2016 Society of Chemical Industry.

Mapping the sensory perception of apple using descriptive sensory evaluation in a genome wide association study.

Breeding apples is a long-term endeavour and it is imperative that new cultivars are selected to have outstanding consumer appeal. This study has taken the approach of merging sensory science with genome wide association analyses in order to map the human perception of apple flavour and texture onto the apple genome. The goal was to identify genomic associations that could be used in breeding apples for improved fruit quality. A collection of 85 apple cultivars was examined over two years through descriptive sensory evaluation by a trained sensory panel. The trained sensory panel scored randomized sliced samples of each apple cultivar for seventeen taste, flavour and texture attributes using controlled sensory evaluation practices. In addition, the apple collection was subjected to genotyping by sequencing for marker discovery. A genome wide association analysis suggested significant genomic associations for several sensory traits including juiciness, crispness, mealiness and fresh green apple flavour. The findings include previously unreported genomic regions that could be used in apple breeding and suggest that similar sensory association mapping methods could be applied in other plants.

Harvest date and crop level influence sensory and chemical profiles of Ontario Vidal blanc and Riesling icewines.

There is likelihood that periods of freezing and thawing endured by icewine grapes change their chemical and sensory profiles. The experimental objective was to determine the influence of harvest date and crop level on icewine sensory profiles and their relationships with chemical variables. Riesling and Vidal blanc (hereinafter "Vidal") icewines were made from four harvest dates in 2004-2005; Harvest 1 (H1): 19 December; H2: 29 December; H3: 18 January; H4: 11 February (Vidal only). Riesling and Vidal icewines were additionally made from three crop level treatments [control (fully cropped), fruit set cluster thinning (i.e. partial fruit removal) to one (basal) cluster per shoot, veraison cluster thinning] and were evaluated over two seasons (2003-2004; 2004-2005). Triangle tests showed differences between harvest date and crop level treatments (both cultivars). Ten and 11 aroma/flavor attributes differed for Vidal and Riesling harvest date icewines, respectively, based upon descriptive analysis by 14 trained tasters. For Vidal, later harvest dates had higher aroma/flavor intensities than H1. Riesling H1 wines had highest fresh fruit descriptor intensities whereas H3 wines were highest for dried fruit and nutty descriptors. Partial least squares regression (PLS) found Vidal icewines described by dried fruit/raisin and honey flavors and viscosity; these attributes were correlated to several aroma compounds and associated with later harvest dates. Sensory differences existed between crop level treatments; thinned treatments had higher fruity, honey, sherry and nut aroma/flavor intensities (both cultivars). PLS showed that sherry flavor was the most important explanatory variable in 2003, and correlated 4-vinylguaiacol and banana flavor in 2004. Overall, harvest date and crop level both affected sensory profiles and chemical composition of Niagara Peninsula icewines.

Aroma compounds in Ontario Vidal and Riesling icewines. I. Effects of harvest date.

Icewine is a sweet dessert wine made from pressing grapes naturally frozen on the vines. It is likely that freeze/thaw cycles endured by icewine grapes change their chemical and sensory profiles due to climatic events. Our objective was to determine the influence of harvest date on icewine must and wine basic chemical variables and aroma compounds. Riesling and Vidal icewines were made from grapes picked between December 2004 and February 2005; Harvest 1 (H1): 19 December; Harvest 2: 29 December; Harvest 3 (H3): 18 January; and Harvest 4 (H4): 11 February (Vidal only). Icewine musts differed in titratable acidity and pH (Vidal only). All basic wine chemical analytes differed across harvest dates. All aroma compounds differed in Vidal and Riesling wines. Highest concentrations for most aroma compounds were in the last harvest date; 16 of 24 for Vidal and 17 of 23 for Riesling. The latest harvest date had highest ethyl isobutyrate, ethyl 3-methylbutyrate, 1-hexanol, 1-octen-3-ol, 1-octanol, cis-rose oxide, nerol oxide, ethyl benzoate, ethyl phenylacetate, γ-nonalactone and ß-damascenone. H1 had highest ethyl butyrate, ethyl hexanoate, linalool, 4-vinylguaiacol and ethyl octanoate. Based on odor activity values, the most odor-potent compounds were ß-damascenone, cis-rose oxide, 1-octen-3-ol, ethyl octanoate, ethyl hexanoate, and 4-vinylguaiacol across harvest dates. PCA found most aroma compounds associated with the last harvest date, 4-vinylguaicol excepted, which was associated with H1. Harvest date was considered a discriminating dimension using canonical variant analysis for volatile compounds.

Aroma compounds in Ontario Vidal and Riesling icewines. II. Effects of crop level.

Icewine is a dessert wine of substantial commercial value to the Canadian wine industry. Many grapegrowers crop icewine-designated vines at levels double those for table wines; therefore, the experimental objective was to ascertain whether reducing crop level might impact icewine chemical and aroma compound profiles. Three treatments [control (fully-cropped); cluster thin at fruit set to one (basal) cluster per shoot (TFS); cluster thin at veraison (TV)] were evaluated in randomized block experiments for Riesling and Vidal over two seasons (2003-04; 2004-05). Treatments differed in must pH and titratable acidity (both years) and although wines differed for most standard chemical variables, no clear trends existed. Vidal icewines had the highest aroma compound concentrations in the control and TV (2003) and in TFS (2004). Most Vidal aroma compounds differed with crop level: 17/24 (2003) and 23/24 (2004). Vidal odor activity values (OAVs) were highest for: ß-damascenone, ethyl octanoate, cis-rose oxide, 1-octen-3-ol, ethyl hexanoate, isoamyl acetate (2003); ß-damascenone, 1-octen-3-ol, ethyl octanoate, cis-rose oxide, and ethyl hexanoate (2004). Principal component analysis (PCA) found ß-damascenone, ethyl 2- and 3-methylbutyrate, ethyl isobutyrate, ethyl butyrate and 1-heptanol correlated and associated with the control (2003), but most compounds were positively loaded on PC1 and associated with replicate, not crop level (2004). All Riesling aroma compounds differed with crop level (2003) and 22/23 (2004). Both years, most aroma compounds were highest in TV and lowest in TFS wines. Riesling OAVs were highest for: ß-damascenone, ethyl octanoate, and ethyl hexanoate (2003, 2004); cis-rose oxide was highly odor potent (2004). PCA of Riesling showed most compounds loaded on PC1 and associated with TV wines (2003). Freeze/thaw events in November/December appeared more important in aroma compound development than adjustment of crop level, and it is therefore concluded that reduction of crop level in Vidal and Riesling vines would not substantially impact icewine aroma composition.

Odor potency of aroma compounds in Riesling and Vidal blanc table wines and icewines by gas chromatography-olfactometry-mass spectrometry.

This study aimed to elucidate the odor potency of aroma compounds in Riesling and Vidal blanc (syn. Vidal) table wines and icewines from the Niagara Peninsula using stir bar sorptive extraction-gas chromatography-olfactometry-mass spectrometry. Dilution analysis determined the most odor-potent compounds in Vidal and Riesling icewines (n = 2) and table wines (n = 2) from a commercial producer. The top 15 odor-potent compounds in each wine were identified and quantified, resulting in 23 and 24 compounds for Riesling and Vidal, respectively. The most odor-potent compounds were ß-damascenone, decanal, 1-hexanol, 1-octen-3-ol, 4-vinylguaiacol, ethyl hexanoate, and ethyl 3-methylbutyrate. In general, icewines had higher concentrations of most aroma compounds compared to table wines. Through computation of odor activity values, the compounds with the highest odor activity for the icewines were ß-damascenone, 1-octen-3-ol, ethyl octanoate, cis-rose oxide, and ethyl hexanoate. In table wines the highest odor activity values were found for ethyl octanoate, ß-damascenone, ethyl hexanoate, cis-rose oxide, ethyl 3-methylbutyrate, and 4-vinylguaiacol. These findings provide a foundation to determine impact odorants in icewines and the effects of viticultural and enological practices on wine aroma volatile composition.