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Assessment of titratable acidity in fruit using short wave near infrared spectroscopy. Part A, Establishing a detection limit based on model solutions

journal contribution
posted on 06.12.2017, 00:00 by Phul SubediPhul Subedi, Kerry WalshKerry Walsh, DW Hopkins
Spectra (700–2500 nm) of citric acid dissolved in water possess features interpreted as being due to the dilution and perturbation of water OH stretching and combination bands (with the second and first overtones of OH stretching at 960 nm and 1420 nm, respectively, and a combination band of OH vibration at 2132 nm) and also to citric acid OH stretching and combination bands and citric acid CH2 bands (first overtone of CH2 stretching at 1680?nm and a combination band of CH2 at 2284 nm). A searching window method was used to optimise the wavelength region for a partial least squares (PLS) regression model development (around 743–904?nm for the region below 1100 nm). Despite the apparent lack of information below1100 nm, a PLS regression model based on transmission spectra (743–904?nm) of pure citric acid–water mixtures (standard deviation = 6.65 g citric acid 100 m–1) yielded a root mean square error of cross-validation (RMSECV) of 0.34% and correlation coefficient of determination (Rcv2) = 0.998. However, if the matrix was varied with 0, 10 and 13% sucrose or fruit juice, RMSECV increased to 0.79%. This RMSECV value is proposed as a benchmark for attempts to assess titratable acidity of juice based on shortwave (700–1100 nm) near infrared spectra of intact fruit collected using silicon diode array instrumentation.

Funding

Category 1 - Australian Competitive Grants (this includes ARC, NHMRC)

History

Volume

20

Issue

4

Start Page

449

End Page

457

Number of Pages

9

eISSN

1751-6552

ISSN

0967-0335

Location

United Kingdom

Publisher

SAGE Publications

Language

en-aus

Peer Reviewed

Yes

Open Access

No

External Author Affiliations

Faculty of Sciences, Engineering and Health; Institute for Resource Industries and Sustainability (IRIS); NIR Consultant (Michigan, USA);

Era Eligible

Yes

Journal

Journal of Near Infrared Spectroscopy