title: Characterization of Grape (Vitis vinifera L.) Berry Sunburn Symptoms by Reflectance.
abstract: Sunburn can affect grape quality both for chemical modifications and by visual impact of the browning. Optical properties of 17 white grape accessions were investigated in the visible region using a noninvasive instrument. Reflectance spectra were obtained using a Jaz System spectrometer. Browning was induced by exposing grape bunches to direct sunlight at 12:30 p.m. for 5 h. During the experiment, the global solar radiation ranged from 2.6 to 2.7 MJ m-2h-1and the air temperature from 24.3 to 29.2 °C; the exposed berries reached a temperature of 34.2 °C in comparison to the 30.4 °C of the shaded ones. Differences between the spectra of controlled and exposed berries mainly emphasized the loss in chlorophyll and the formation of brown compounds. A positive correlation between the chlorophyll concentration and berry browning was proposed. Developing rapid, noninvasive, and low-cost methods based on reflectance spectroscopy could support grapevine variety characterization with respect to sunburn susceptibility as well as study of the physiological processes involved in the symptoms' appearance.
authors.affiliation: CIRIVE - Centro Interdipartimentale di ricerca per l'innovazione in Viticoltura ed Enologia, Università degli Studi di Milano , via G. Celoria 2, I-20133 Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Rustioni
authors.affiliation: CIRIVE - Centro Interdipartimentale di ricerca per l'innovazione in Viticoltura ed Enologia, Università degli Studi di Milano , via G. Celoria 2, I-20133 Milano, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Rocchi
authors.affiliation: CIRIVE - Centro Interdipartimentale di ricerca per l'innovazione in Viticoltura ed Enologia, Università degli Studi di Milano , via G. Celoria 2, I-20133 Milano, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Guffanti
authors.affiliation: CIRIVE - Centro Interdipartimentale di ricerca per l'innovazione in Viticoltura ed Enologia, Università degli Studi di Milano , via G. Celoria 2, I-20133 Milano, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Cola
authors.affiliation: CIRIVE - Centro Interdipartimentale di ricerca per l'innovazione in Viticoltura ed Enologia, Università degli Studi di Milano , via G. Celoria 2, I-20133 Milano, Italy.
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Failla
keywords: Vitis vinifera; browning symptoms; melanin-like pigments; sun exposure; white grapes