title: Estimation of total soluble solids in grape berries using a hand-held NIR spectrometer under field conditions.
abstract: BACKGROUND
  Recent studies have reported the potential of near infrared (NIR) spectral analysers for monitoring the ripeness of grape berries as an alternative to wet chemistry methods. This study covers various aspects regarding the calibration and implementation of predictive models of total soluble solids (TSS) in grape berries using laboratory and in-field collected NIR spectra.
  
  
  RESULTS
  The performance of the calibration models obtained under laboratory conditions indicated that at least 700 berry samples are required to assure enough prediction accuracy. A statistically significant error reduction (ΔRMSECV = 0.1°Brix) with P < 0.001 was observed when measuring berries without epicuticular wax, which was negligible from a practical point of view. Under field conditions, the prediction errors (RMSEP = 1.68°Brix, and SEP = 1.67°Brix) were close to those obtained with the laboratory dataset (RMSEP = 1.42°Brix, SEP = 1.40°Brix).
  
  
  CONCLUSIONS
  This work clarifies several methodological factors to develop a protocol for in-field assessing TSS in grape berries using an affordable, non-invasive, portable NIR spectral analyser. © 2015 Society of Chemical Industry.
authors.affiliation: Universidad de La Rioja, 26006, Logroño, Spain.
authors.forename: Ruben
authors.initials: R
authors.lastname: Urraca
authors.affiliation: Division of Biosciences, University of Helsinki, Viikinkaari, 5 E, P.O. Box 56, 00014, Helsinki, Finland.
authors.forename: Andres
authors.initials: A
authors.lastname: Sanz-Garcia
authors.affiliation: Instituto de Ciencias de la Vid y del Vino, University of La Rioja, CSIC, Gobierno de La Rioja, 26006, Logroño, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Tardaguila
authors.affiliation: Instituto de Ciencias de la Vid y del Vino, University of La Rioja, CSIC, Gobierno de La Rioja, 26006, Logroño, Spain.
authors.forename: Maria P
authors.initials: MP
authors.lastname: Diago
mesh_terms: D002138:Calibration; D000069599:Crop Production / Q000592:standards; D018556:Crops, Agricultural / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D000068598:Data Accuracy; D016208:Databases, Factual; D005513:Food Inspection / Q000295:instrumentation* / Q000592:standards; D063427:Food Quality; D005638:Fruit / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D017408:Guidelines as Topic; D008422:Materials Testing; D015233:Models, Statistical; D025341:Principal Component Analysis; D011786:Quality Control; D012031:Refractometry; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012995:Solubility; D013030:Spain; D019265:Spectroscopy, Near-Infrared; D027843:Vitis / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D014885:Waxes / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism; D014920:Wine / Q000032:analysis / Q000592:standards
chemical_list: D014885:Waxes
keywords: NIR spectroscopy; chemometrics; non-invasive sensor; precision viticulture; total soluble solids content