Rapid analysis of sugar content of intact orange fruit using ultraviolet and visible transmittance techniques

Abstract

Sugar content (SC) is very important factors of navel orange internal quality and can be measured non-destructive by visible and near infrared spectroscopy. The feasibility of visible and near infrared spectroscopy for nondestructively measuring SC of navel orange fresh juices was investigated by means of spectral transmittance technique. A total 55 juice samples were used to develop the calibration and prediction models. Three different kinds of mathematical treatments (original, first derivative and second derivative) of spectra in the range of 400-800 nm were discussed and two kinds of reference standards were used. Different spectra correction algorithms (constant, multiplicative signal correction (MSC) and standard normal variate (SNV) were compared. Three kinds of calibration models including partial least square (PLS) regression, stepwise multiple linear regression (SMLR) and principle component regression (PCR) were evaluated for the determination of SC in navel orange juice. Performance of different models was assessed in terms of root mean square errors of prediction (RMSEP) and correlation coefficient (r) of validation set of samples. The correlation coefficients of calibration models for SC was 0.97, the correlation coefficients of prediction models for SC was 0.86, and the corresponding RMSEP was 0.56. The results show that visible near infrared transmittance technique is a feasible method for non-destructive measurement of sugar content of fruit juice.