IoT-based microcontroller system for monitoring the organoleptic aroma of post-harvest coffee

Abstract

This paper presents the development of a low-cost electronic system designed to indirectly monitor the organoleptic attributes of coffee during the post-harvest stage, with the purpose of differentiating states such as cherry coffee, honey coffee, and dry parchment coffee. The system integrates MQ3 and MQ135 gas sensors, used to detect compounds associated with fermentation processes and the release of volatile organic compounds, together with a DHT11 sensor for measuring ambient temperature and humidity. Data acquisition and processing are carried out through an ESP32 microcontroller programmed in the Arduino® IDE, enabling local storage on a microSD card, visualization through a graphical interface developed in MATLAB®, and wireless transmission to the IoT platform ThingSpeakTM for remote monitoring. Experimental tests conducted in different post-harvest states revealed differentiated patterns in relative alcohol concentration, levels of volatile compounds, and humidity, consistent with the evolution of fermentation and drying processes. Qualitative validation with a coffee expert confirmed the potential of the system as an accessible and useful tool for post-harvest analysis and monitoring, contributing technological innovation to quality control in the coffee sector.