Determination of Physical, Acoustical, Mechanical, and Chemical Properties of Fresh Young Coconut Fruit for Maturity Separation

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Abstract Young coconut is a popular tropical fruit featuring soft white aromatic flesh and sweet white or transparent juice. As most coconut pickers are relatively unskilled, the harvested crop tends to be distinguished by the collection of fruit of varying levels of maturity. This research has sought to improve the accuracy of grading-packaging systems by developing correlations between maturity levels and the physical, acoustical, mechanical, and chemical properties of the fruit. Results show that maturity significantly affects the specific gravity, shell rupture force, shell secant modulus, flesh penetrating force, flesh firmness, total soluble solids, titratable acidity, flesh thickness (FT), and natural frequency of young coconut at p<0.05. The FT expressed the highest linear correlation with maturity among the properties observed. Fruit orientation, sound impact point, and maturity significantly affected the natural frequency of young coconut at p<0.05. Impacting the ridge of a young coconut gave significantly different natural frequency with maturity regardless of the impact position. The optimum impact point was observed to be midway between the fruit equator and the stem on the ridge. Applying the defined physical and chemical properties to the discriminant model, the maturity of young coconut could be classified with an accuracy of 94.0 %. Analysis employing partial least squares regression predicted the relationship between the maturity index, represented by the FT and the physical, sound, mechanical, and chemical properties, with a correlation coefficient (R) value of 0.82 and a root mean squared error of prediction value of 1.03.