The aim of the study was to determine the effect of late-season Shiraz berry dehydration (berry shrivel) on the chemical and sensory properties of the resulting wine.
PROJECT LAYOUT
- Shiraz grapes were harvested on 25 February 2016 from a commercial vineyard (8 – 10 t/ha) in New South Wales, Australia.
- Grape bunches were manually sorted into two groups: shrivelled and non-shrivelled. Grape bunches with 80% or more shrivelled berries were classified as shrivelled. The individual shrivelled berries in the non-shrivelled bunches were manually removed.
- 25 kg of grapes were fermented in triplicate for each treatment in 100L stainless steel tanks.
- pH was adjusted with tartaric acid to 3.6 three times during the winemaking process.
- Fermentation was conducted with EC 1118 between 24 and 28°C.
- The must was inoculated one day after the start of alcoholic fermentation with MLF culture: Enoferm Alpha.
- YAN was adjusted to 250 mg/L with DAP and Fermaid A after the onset of fermentation.
- The wine was pressed, cold stabilised and bottled.
- Various chemical analyses were conducted on the juice and wine.
- Descriptive sensory analysis was conducted by a trained panel two months after harvest.
MAIN RESULTS
- Basic grape juice parameters were similar for shrivelled and non-shrivelled berries.
- Wine made from shrivelled berries had 1% percentage alcohol more than wine made from non-shrivelled berries, despite initial Brix values being similar for the two treatments. It is hypothesized that it is probably due to raisin-like berries in the shrivelled grapes that remained intact after initial crushing, and only released their sugars during fermentation.
- Wine colour parameters indicated faster oxidative ageing for the shrivelled berries wine.
- Shrivelled berries wine had lower concentrations of fruity acetate esters.
- Berry shrivelling did not affect amino acid content and YAN.
- Massoia lactone (cooked and dry fruit) and ƴ-nonalactone (prune) concentrations were higher in wines made from shrivelled berries.
- Sensory analysis revealed wines from shrivelled berries to be more alcoholic and astringent, and higher in dark and stewed fruit aromas than wines from non-shrivelled berries.
- Wines from non-shrivelled berries had a higher perception of red fruit notes and acidity.
SIGNIFICANCE OF THE STUDY
The study indicated the influence that berry shrivel can have on wine chemical and sensory properties and underscores the importance of pre-fermentation sorting of grapes in order to ensure desired sensory outcomes.
REFERENCE
Hsiao-Chi Chou, Katja Å uklje, Guillaume Antalick, Leigh M. Schmidtke and John W. Blackman (2018). Late-season Shiraz berry dehydration that alters composition and sensory traits of wine. Journal of Agricultural and Food Chemistry 66 (29), 7750-7757. DOI:Â 10.1021/acs.jafc.8b01646
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