Research Progress of Single/Multi-Mode Optical Sensors on Visual Monitoring of Food Freshness: A Review.

As a critical issue impacting public health and social development, food safety calls for the advancement of efficient, precise, and easily implementable detection technologies to ensure food quality. In recent years, optical sensors have demonstrated significant advantages in food freshness monitoring due to their high sensitivity, excellent selectivity, and real-time response capabilities (e.g., detection limits: 5.1 nm for BAs, 0.3 µm for H2S; response times: 3 s-30 min; detection ranges: pH 3-9, analyte concentrations from nm to mm). This paper systematically reviews the latest progress in single-mode, dual-mode, and multi-mode optical sensors, focusing on their performance in detecting key biomarkers-such as biogenic amines, hydrogen sulfide, and organic acids-during the storage of perishable foods. Research indicates that the introduction of novel functional materials, including metal-organic frameworks, natural pigments, and carbon dots, significantly enhances sensor performance. Meanwhile, the integration of smartphone visual recognition with deep learning algorithms is driving the development of integrated signal acquisition and analysis systems. Although challenges remain in areas such as resistance to environmental interference, simultaneous multi-parameter detection, and commercial packaging, interdisciplinary collaboration and sustainable material innovation hold the promise of establishing optical sensing technology as a key enabler for building intelligent, food quality and safety monitoring systems.