|Authors: ||P. Prosperi, R. Botondi, A. Bellincontro, D. DeSantis, F. Mencarelli|
|Keywords: ||grape, dehydration, VOCs, respiration|
Some special wines are usually obtained from dried grapes by using traditional techniques without control of temperature, relative humidity (RH) and airflow.
A new technology (tunnel) for grape dehydration based on controlled air speed, temperature and RH has been tested on 'Pecorino' grape and compared with traditional practice of grape dehydration.
The grapes were harvested at 21 °Brix of solid soluble content (SSC). The tunnels (2) dried the grapes at 15°C, 60% of RH, and air flow of 1.2 or 2.5 m s-1. Control grapes were kept in a room with open windows but without controlled environment of dehydration.
Vapour pressure deficit (VPD) in the two tunnels was always between 7.5 and 8.0 mbar while, in the control, VPD fluctuated between 0.7 and 6.4 mbar with temperature between 25 and 7°C, depending on the outside temperature conditions.
The dehydration lasted until the time of reaching 45% mass loss (m.l.). SSC reached 32 °Brix in tunnel samples and 26 °Brix in control one.
CO2 production of grapes showed a peak in all 3 samples at 10% m.l. then it declined and rose again in control sample, reaching the highest value at 17% m.l. while, in the tunnel samples, it reached a peak at 30 and 40% m.l. for 1.2 and 2.5 m s-1 tunnels, respectively.
Significant difference in volatile organic compounds (VOCs) was observed between the samples at the last sampling, where the concentration of alcohols was much higher than esters and aldehydes in control sample and it was much higher than the same compounds in the tunnel sample.
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