Selection of the temperature in the sugar content determination of kiwi fruit

In the last few years, the production of kiwifruit (Actinidia deliciosa) has undergone a significant development with increasing international market. Therefore, the use of fast and non-destructive methods for ripening control is desirable. In this sense, NIRS technology (Near Infrared Spectroscopy) has proved to be very useful. The objectives of this work were to estimate the soluble solids content from NIRS technology and to evaluate the influence of the kiwifruit temperature on the NIR measures. A sample of 210 fruits was collected and stored for three months under cold conditions. The NIR measures were done at three kiwifruit temperatures (0.5 degrees C, 10 degrees C and 20 degrees C) and the refractometric index was determined at the end of the experiment. The reflectance spectra in the near-infrared region between 800 and 2500 nm were measured with a Varian CARY 500 spectrophotometer equipped with an integrated sphere to measure reflectance in solid samples. The information has been analysed with Unscramble and SPSS statistical programs, which include a wide range of rapid data-processing applications and procedures, with a large number of options and graphic representations. The test performed for this study are PLS (partial least squares regression) and DA (discriminate analysis). Results showed: the validity of this technology to obtain a relationship between the NIRS and the soluble solids content, and differences on the wavelengths used in the calibrations, depending on the kiwifruit temperature.