Evaluation of watermelon ripeness using self-developed ripening detector

Abstract

Currently the evaluation of watermelon ripeness is performed manually by tapping the surface of fruit or by visually evaluating from its appearance. However, these evaluations are subjective and inconsistent, therefore, it is necessary to develop and use a reliable instrument for this purpose. This study aimed to develop a ripening detector apparatus based on acoustic impulse response and to be used for evaluating the ripeness stage of watermelon. In this study, five different maturity ages of watermelon, namely 39, 43, 47, 51, and 55 days after planting were evaluated. The acoustic responses were recorded using Audacity 2.3.1. The dominant frequencies and magnitude were then analyzed using Matlab R2014b. The acoustic parameters were related to fruit weight and soluble solid contents to distinguish the different maturity stages. The results showed that the dominant frequencies and the magnitudes were clearly related to the fruit weight and soluble solid contents. As the frequencies and the magnitudes decreased the fruit weight and soluble solids contents consistently increased during maturity period. Therefore, this finding confirmed that the developed ripening detector was reliable to evaluate and distinguish the different ripeness stage of watermelon.