Food spoilage is a major contributor to foodborne illness and economic loss across households, retail stores, and supply chains. Conventional inspection of food quality relies on visual appearance, odour, and expiry labelling, all of which are subjective and often fail to detect early-stage microbial decomposition. This paper presents the design and implementation of a low-cost, real-time Internet of Things (IoT) based Food Quality Monitoring and Alert System capable of continuously assessing the freshness of perishable items such as fruits, vegetables, meat, and dairy products. The system integrates semiconductor gas sensors (MQ-3/MQ-4/MQ-135) with a DHT22 temperature and humidity sensor, both interfaced to an ESP32 microcontroller that forms the central processing unit. The ESP32 evaluates sensor readings against calibrated spoilage thresholds and drives local indicators, an LCD display, a buzzer alarm, and an LED status indicator, while simultaneously publishing data over Wi-Fi to a cloud-based IoT dashboard for remote monitoring on a PC or mobile device. Experimental trials on a small sample of fresh and ageing food items demonstrate that the prototype reliably differentiates “fresh,” “moderately fresh,” and “spoiled” conditions on the basis of volatile organic compound (VOC) concentration and ambient humidity trends, with an alert latency of under three seconds. The proposed system offers a scalable, low-power, and inexpensive alternative to manual food inspection, with applications in home kitchens, cold storage, and food supply chain monitoring.

Index Terms— Food Quality Monitoring, Internet of Things (IoT), ESP32, MQ-135 Gas Sensor, DHT22, Electronic Nose, Food Spoilage Detection, Smart Alert System.