By definition, nanomaterials have at least one dimension between 1 and 100 nm, where nm stands for nanometers, and these extremely small dimensions result in a high surface-to-volume ratio, which gives rise to unique properties. For example, incorporating nanoparticles into food packaging significantly improves its performance, such as mechanical strength and barrier properties.

Furthermore, compared to non-nanoscale materials, they exhibit high antimicrobial activity and high reactivity 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 reinforcements but also enable active functions such as spoilage detection and real-time freshness monitoring.

A review by A. Muthu et al. (2025) provides a comprehensive overview of nanomaterials used in 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 enhance their properties, such as strength, gas barrier efficiency, and heat resistance.

Use of Nanosensors

This section outlines the practical applications of nanomaterials incorporated into packaging, while also describing the various 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, more generally, colored substances that change color in response to stimuli such as changes in pH or the presence of volatile gases produced by food spoilage. These indicators provide a simple, visual representation of changes in food quality. The nanoscale dimensions amplify color changes, making them visible even in response to minimal fluctuations in pH or gas concentration, thereby enabling 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 detection of spoilage;
• fluorescence. Fluorescent indicators emit visible signals when they interact with molecules produced by foods and associated with 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 its earliest stages. These systems have been used for the 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 them. These sensors enable precise environmental monitoring inside the package;
• monitoring by Time-Temperature Indicators (TTIs), which record the thermal exposure of food products, making them indispensable in cold chain logistics, especially for perishable goods. TTIs incorporating “nano” technology typically use temperature-sensitive dyes embedded in biopolymer matrices (e.g., polylactic acid, PLA). These dyes undergo irreversible color changes in response to temperature fluctuations and thus serve as visual indicators of a food’s thermal history;
• 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 we have seen, the incorporation of nanosensors into biodegradable films or edible coatings plays a fundamental role in enhancing food safety, extending shelf life, minimizing waste, and adopting environmentally sustainable packaging solutions, as they enable real-time detection of freshness and changes within the packaging. However, for large-scale use, several technological challenges must first be overcome.

The small size and high reactivity of nanomaterials raise concerns regarding 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 evaluation criteria is essential. Therefore, robust regulatory frameworks will be required in the future to ensure the safe and practical application of nanotechnologies in food systems.

References: Muthu et al., University of Debrecen, Hungary (Foods 14, 2025, 2657).