Ultraviolet-visible transmittance techniques for rapid analysis of sugar content and soluble solids content of fresh navel orange juices

Abstract

Sugar content (SC) and soluble solids content (SSC) are very important factors of navel orange internal quality and can be measured non-invasively by ultraviolet-visible spectroscopy techniques. The feasibility and methods of ultraviolet-visible spectroscopic techniques for rapid quantifying SC and SSC of navel orange fresh juices was investigated by its spectral transmittance. A total 55 juice samples were used to develop the calibration and prediction models. Different spectra correction algorithms (constant, multiplicative signal correction (MSC) and standard normal variate (SNV) were compared in our work. Three different kinds of mathematical spectra treatments (original, first derivative and second derivative) of spectra in the range of 200-800 nm and two kinds of reference standards were also investigated. Three kinds of models including partial least square regression (PLSR), stepwise multiple linear regression (SMLR) and principle component regression (PCR) were evaluated for the determination of SC and SSC in navel orange juice. Calibration models based on the different spectral ranges were also compared. Performance of different models was assessed in terms of root mean square errors of prediction (RMSEP) and correlation coefficient (r) of prediction set of samples. The correlation coefficients of calibration models for SC and SSC were 0.965 and 0.961, the correlation coefficients of prediction models for SC and SSC were 0.857 and 0.888, and the corresponding RMSEP were 0.562 and 0.492 respectively. The results show that ultraviolet-visible transmittance technique is a feasible method for non-invasive estimation of fruit juice SC and SSC.