Postharvest dehydration of Nebbiolo grapes grown at altitude is affected by time of defoliation

作者：Nicoletti I; Bellincontro A; De Rossi A; De Sanctis F; Tiberi D; Pietromarchi P; Botondi R; Corradini D; Mencarelli F^*

来源：Australian Journal of Grape and Wine Research, 2013, 19(3): 358-368.

DOI：10.1111/ajgw.12042

• defoliation
• dehydration
• Nebbiolo
• phenolic substances

Background and AimsSfursat is an Italian wine produced with partially dehydrated Nebbiolo grapes in the Valtellina region which is located at high altitude. The research aims to understand the influence of fruit exposure on the rate of water loss by harvested fruit and the influence of exposure and dehydration on the content of phenolic substances and anthocyanins in the wine.
Methods and ResultsClusters of Nebbiolo grapes from control vines (ND) and from vines that were defoliated at fruitset (DFS) or post-veraison (DPV) were harvested at a sugar concentration of about 230g/L (there was no significant difference among the treatments), and dehydrated at 10, 20 or 30 degrees C and at 60% relative humidity (RH), and air flow. Fruit were sampled at 10 and 20% weight loss (WL). Leaf removal had little effect on the physical characteristics of bunches and on the anthocyanins content and profile of harvested Nebbiolo grapes but affected dehydration. At 10 and 20 degrees C, DFS fruit lost mass more slowly than DPV and ND fruit. In ND fruit, 20% WL reduced anthocyanins from 554mg/kg fresh mass (FM) at harvest to 458, 432 and 396mg/kg FM at 10, 20 and 30 degrees C, respectively. In DFS and DPV berries, anthocyanins increased during dehydration at 10 degrees C. At harvest, ND berries had a lower content of total stilbenes than those from defoliated vines. Dehydration (10 degrees C, 20% WL) increased stilbene concentration in ND and DPV fruit. Dehydration at 10 degrees C induced a rise in the flavonol concentration in fruit from defoliated vines. Catechin concentration was 106.5mg/kg DM (dry mass), the highest value in ND berries at harvest. Wine was produced only from grapes dehydrated at 10 degrees C. Wine from DFS fruit had a higher content of phenolic substances (2704.8mg/L) and anthocyanins (104mg/L) than that from DPV (2454.9 and 96.2mg/L, respectively) and ND (2301.9 and 100.5mg/L, respectively) fruit.
ConclusionsPostharvest dehydration was slower where vines had been defoliated and resulted in changes in the ratios among groups of phenolic substances as well as among single phenolic components.
Significance of the StudyIn Nebbiolo grapes for Sfurzat wine production, defoliation at fruit set enables fruit to reach phenolic maturity at a lower sugar concentration allowing dehydration to increase sugar concentration without producing excessively alcoholic wines.

• 出版日期2013-10