title: Rapid monitoring of grape withering using visible near-infrared spectroscopy.
abstract: BACKGROUND
  Wineries need new practical and quick instruments, non-destructive and able to quantitatively evaluate during withering the parameters that impact product quality. The aim of the work was to test an optical portable system (visible near-infrared (NIR) spectrophotometer) in a wavelength range of 400-1000 nm for the prediction of quality parameters of grape berries during withering.
  
  
  RESULTS
  A total of 300 red grape samples (Vitis vinifera L., Corvina cultivar) harvested in vintage year 2012 from the Valpolicella area (Verona, Italy) were analyzed. Qualitative (principal component analysis, PCA) and quantitative (partial least squares regression algorithm, PLS) evaluations were performed on grape spectra. PCA showed a clear sample grouping for the different withering stages. PLS models gave encouraging predictive capabilities for soluble solids content (R(2) val  = 0.62 and ratio performance deviation, RPD = 1.87) and firmness (R(2) val  = 0.56 and RPD = 1.79).
  
  
  CONCLUSIONS
  The work demonstrated the applicability of visible NIR spectroscopy as a rapid technique for the analysis of grape quality directly in barns, during withering. The sector could be provided with simple and inexpensive optical systems that could be used to monitor the withering degree of grape for better management of the wine production process.
authors.affiliation: Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy (DiSAA), Università degli Studi di Milano, 20133, Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Beghi
authors.affiliation: Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy (DiSAA), Università degli Studi di Milano, 20133, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Giovenzana
authors.affiliation: Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy (DiSAA), Università degli Studi di Milano, 20133, Milan, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Marai
authors.affiliation: Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy (DiSAA), Università degli Studi di Milano, 20133, Milan, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Guidetti
mesh_terms: D000465:Algorithms; D005421:Flavoring Agents / Q000032:analysis; D019649:Food Industry / Q000379:methods*; D005638:Fruit / Q000378:metabolism; D006244:Hardness; D006801:Humans; D007558:Italy; D016018:Least-Squares Analysis; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013649:Taste; D027843:Vitis / Q000378:metabolism; D014867:Water / Q000378:metabolism; D014920:Wine / Q000032:analysis* / Q000592:standards
chemical_list: D005421:Flavoring Agents; D014867:Water
keywords: chemometrics; firmness; grape withering; postharvest; soluble solids content; visible NIR spectroscopy