The current research status of non-destructive testing technologies for egg quality: internal freshness - a review

1. Traditional methods of assessing egg freshness, such as sensory evaluation and specific gravity testing, are labour-intensive and destructive. However, non-destructive testing (NDT) technologies offer significant advantages in terms of speed, accuracy and non-invasiveness, enabling real-time monitoring of egg quality during production, transportation, storage and sale.2. A review was conducted to evaluate various NDT techniques, including optical methods (such as visible - near infrared spectroscopy and hyperspectral imaging), acoustic methods (such as ultrasonic transmission and reflection analysis), electrical methods (such as dielectric spectroscopy) and emerging technologies (such as low-field nuclear magnetic resonance, electronic nose and infrared thermal imaging).3. These technologies have advanced significantly in accuracy and real-time performance. Among optical methods: visible - near infrared spectroscopy (R²  = 0.90) and hyperspectral imaging (R²  = 0.918). Acoustic technologies: ultrasonic phase velocity correlated significantly with Haugh unit (HU)/air cell height (p < 0.05), with a HU model correlation of R²  = 0.87. Electrical methods: dielectric spectroscopy + algorithms achieved 100% classification accuracy; capacitive sensing + machine vision yielded R²  > 0.994. Emerging technologies enhanced sensitivity. However, challenges remain in terms of equipment cost, sample variability, lack of unified standards and the integration of multi-source data with artificial intelligence.4. The widespread application of these technologies can be expected to significantly improve the efficiency, safety and sustainability of the egg supply chain.