English abstract
Date fruit (Phoenix dactylifera) is one of the most ancient edible fruits in the Arab world. About 61% of the fresh weight of the fruit contains total soluble solid (TSS). TSS content of a date fruit is an important commercial attribute for quality analysis. At present, TSS content of date is being measured using destructive techniques that are laborious and time consuming. Therefore, the objective of this study was to evaluate the potential of Near Infrared (NIR) imaging technique to determine TSS content of dates nondestructively. 'Fardh', 'Khalas' and 'Naghal' varieties of dates at Tamar stage and 'Khalas' variety at two ripening stages (Khalal and Tamar) were collected for TSS determination (n = 400 date fruits in each category). These date varieties are most common in Oman and having significantly different TSS content. The digital NIR camera which covers the full spectrum range from 900 to 1700 nm (SU320KTS-1.7RT, Goodrich, USA) was used for capturing the images of three varieties and two ripening stages. Immediately following image acquisition, the TSS content ('Brix) of each sample was measured using a digital refractometer (PR-320, Palette, ATAGO, CO. LTD., Japan). A multiple linear regression (MLR) model along with dummy variable concept was established between measured TSS and NIR reflectance for varieties and for ripening stages, respectively. It showed that TSS and reflectance were inversely proportional to each other and the percentage of reflectance changed significantly (a=0.05) depending on TSS. The correlation coefficient (r) between TSS content and NIR reflectance was obtained to be 0.62 for three varieties and 0.98 for two ripening stages. It evidenced that NIR imaging technique has potential possibility to use as a nondestructive TSS measurement tool for dates.
Keywords: NIR imaging, Dates, Reflectance, Total Soluble Solid (TSS), Multiple Linear Regression (MLR).
