The development of a device and method to evaluate the precise harvesting time of tropical agricultural commodities based on acoustic properties

Non-climacteric agricultural products are the commodity that cannot mature after being harvested so it is necessary to determine the right harvesting time to obtain the best quality. Generally, farmer will determinate the maturity of those commodity using a sound response from fruit tapping in addition to seeing the visual appearance. However, this is subjective so it is necessary to develop a more reliable and practical method. In this study a knocker maturity detection tool had been build and was used to evaluate three types of non-climacteric commodity, namely seedless watermelon aged 51, 54, 57, 60 DAP, eggplants aged 42, 44, 46, 48 DAP and cucumbers aged 27, 28, 29, 30 DAP. The knocking sound was recorded using Audacity 2.3.1 and then analyzed the frequency and magnitude parameters using Matlab R2014b. The results obtained were related to the physicochemical parameters of the samples. The results showed that the constructed knocker was able to distinguish the level of fruit maturity. In addition, it was also known that the right time for harvesting watermelon was 89 Hz or 50 dB, eggplant 157 Hz or 54 dB, and cucumber was 218 Hz or 52 dB.