Analysis of apples varieties – comparison of electronic tongue with different analytical techniques

The present study was aimed at application of rapid analytical techniques such as Electronic Tongue and FTIR spectroscopy to the recognition and quantitative analysis of different apple varieties. Five apple varieties were studied using three different analytical techniques: HPLC, electronic tongue multisensor system based on potentiometric chemical sensors and FTIR spectroscopy. Twenty samples (apples) of each variety were measured. Concentrations of organic acids such as malic, citric, galacturonic etc. and sugars were measured by HPLC, which is a conventional method for fruit analysis. HPLC data were used as reference for calibration of the electronic tongue and FTIR. Different aspects of data processing were addressed. Recognition and classification of the apples according to variety was performed by PCA and PLS DISCRIM using the data from three different analytical instruments. Quantitative calibration of the electronic tongue and FTIR with respect to organic acids content was performed using PLS regression. Different approaches to data merging from two different analytical instruments, ET and ATR-FTIRT, were considered. Low-level data fusion was found to be the most effective for ET and ATR-FTIR.