By definition, nanomaterials have at least one dimension between 1 and 100 nm, where nm stands for nanometers, and these very small dimensions lead to a high surface area to volume ratio, resulting in unique properties. For example, incorporating nanoparticles into food packaging leads to significantly improved performance, such as mechanical strength and barrier properties. Furthermore, compared to non-nanometer materials, they exhibit high antimicrobial activity and high responsiveness to environmental stimuli (such as temperature, pH, gas composition, or humidity) through controlled and predictable changes in their optical, thermal, electrical, or magnetic properties. Therefore, they not only serve as passive reinforcement but also enable active functionalities such as spoilage detection and real-time freshness monitoring. A review by A. Muthu et al. (2025) provides a comprehensive overview of nanomaterials used as smart and sustainable food packaging, focusing on their role in real-time spoilage detection and food traceability. The review highlights the role of various types of nanomaterials, such as metals, metal oxides, and carbon-based structures, in improving food safety, quality, and sustainability. Furthermore, when combined with biopolymer matrices, nanomaterials can significantly improve their properties, such as strength, gas barrier efficiency, and heat resistance.

Use of nano-sensors

This section outlines the practical applications of nanomaterials incorporated into packaging, while also highlighting their different mechanisms of action, which are based on colorimetry, fluorescence, reactions with gases, and time-temperature variations:

• Colorimetry. Colorimetric indicators use natural pigments (e.g., anthocyanins, curcumin, etc.) or generally colored substances that change color in response to stimuli such as pH changes or the presence of volatile gases produced by food spoilage. These indicators provide a simple, visual representation of changes in food quality. Nanoscale dimensions amplify color changes, which are then visible following minimal fluctuations in pH or gas concentration, thus allowing earlier detection of spoilage compared to non-nanoscale materials. Specifically, films based on nanoscale anthocyanins extracted from red cabbage and incorporated into biodegradable matrices have been successfully used to monitor the freshness of meat and seafood; Zinc oxide-based nanoparticles have been incorporated into films to provide low-cost, highly pH-sensitive spoilage detection;
• Fluorescence. Fluorescent indicators emit visible signals when they interact with molecules developed by foods and related to their spoilage, such as hydrogen sulfide and volatile amines. In addition to visible color changes, fluorescent indicators offer high sensitivity and can detect spoilage even in the early stages of development. These systems have been used for rapid, non-destructive monitoring of dairy product spoilage;
• Detection of gases, such as ammonia, hydrogen sulfide, carbon dioxide, and ethylene, which are commonly produced by food spoilage. These gases are detected by nanosensors embedded in the packaging, such as tin dioxide, which interacts with these gases. These sensors enable precise environmental monitoring within the package;
• detection by Time-Temperature Indicators (TTIs), which record the thermal exposure of food products, making them indispensable in cold chain logistics, especially for perishable products. TTIs integrated with nanotechnology typically use temperature-sensitive dyes incorporated into biopolymer matrices (e.g., polylactic acid, PLA). These dyes undergo irreversible color changes following temperature changes and thus serve as visual indicators of the thermal history of foods;
• antimicrobial properties, related to the small size of the nanoparticles, which can effectively neutralize microorganisms. Silver, copper, and zinc oxide nanoparticles are widely used for their broad-spectrum antimicrobial properties, particularly in room-temperature storage. For example, silver-coated cellulose films exhibit potent activity against foodborne pathogens.

Challenges and future directions for nanosensors

As seen, incorporating nanosensors into biodegradable films or edible coatings plays a key role in increasing food safety, extending shelf life, minimizing waste, and adopting environmentally sustainable packaging solutions, as they enable real-time detection of freshness and changes within packaging. However, large-scale deployment requires overcoming several technological challenges. The small size and high reactivity of nanomaterials raise concerns about their migration into food and potential long-term effects on human health and the environment. Unclear regulations, especially in developing countries, further complicate the path to commercialization. In this regard, establishing standardized risk assessment protocols and safety assessment criteria is crucial. Therefore, robust regulatory frameworks will be required in the future to ensure the safe and practical application of nanotechnologies in food systems.

Bibliographic references: A. Muthu et al., dell’Università di Debrecen, Ungheria (Foods 14, 2025, 2657).