Enhancing seafood freshness monitoring: Integrating color change of a food-safe on-package colorimetric sensor with mathematical models, microbiological, and chemical analyses

Abstract

The study assessed a developed food-safe on-package label as a real-time spoilage indicator for fish fillets. This colorimetric sensor is sensitive to Total Volatile Base Nitrogen (TVB-N) levels, providing a correct indication of fish freshness and spoilage. This study evaluates and predicts the shelf-life and effectiveness of an on-package colorimetric indicator. The sensor, using black rice (BC) dye with polyvinyl alcohol (PVOH), polyethylene glycol (PEG), and citric acid (CA) as binders and crosslinking agents, is applied to PET films. The food-safe pH indicator, prepared via lab-scale flexography printing, is durable in humid environments, making it suitable for practical packaging scenarios. The sensor visibly monitored fish spoilage at 4 °C for 9 days. Quality assessment included tracking ΔRGB (total color difference), chemical (TVB-N, pH), and microbiological analyses. Results indicate that the fish samples are fresh up to 4 days of storage at 4 °C; the total viable count (TVC), Pseudomonas growth, TVB-N contents and pH reached: 5.2 (log CFU/ml), 4.31(log CFU/ml), 26.22 (mg N/100 gr sample) and 7.48, respectively. Integrating colorimetric sensor data with mathematical modeling can predict spoilage trends over time. Integrated system offers a smart approach to accurately predicting shelf-life, aiding in optimizing storage conditions, minimizing food waste, and delivering fresh, high-quality fish products to consumers.

Keywords: Anthocyanin; Fish spoilage; Intelligent packaging; On-package sensor; Quality assessment; pH indicator.

Graphical abstract

Fig. 1

TGA thermogram for each component of formulated ink as an ink sensor.

Fig. 2

TGA thermogram for the dried ink solution (at room temperature) on the Petri dish, developed pH indicators that were thermally treated at 165 °C for 5 min (INK I TT) and those that were not heated (INK I NTT).

Fig. 3

The color parameters, sensitivity and color change outcomes for NTT pH indicators (package headspace) at different pH level for their coatings, were stored at 4 °C over 9 days.

Fig. 4

Illustrates the color change outcomes for pH indicators (container headspace) were stored at 4 °C over 9 days. NTT; colorimetric films without heat treatment.TT; colorimetric films with exposure to heat (165 °C) for specific time (5 min). Fish condition at day 4: acceptable; day 6: marginal; day 9: spoiled.

Fig. 5

The RGB value of TT pH indicators towards 100 μL of diluted NH₃ under accelerated storage conditions (T = 60 for 30 min).

Fig. 6

The RGB value of TT pH indicators towards 100 μL of diluted TMA under accelerated storage conditions (T = 60 for 30 min).

Fig. 7

The RGB value of TT pH indicators towards 100 μL of diluted DMA under accelerated storage conditions (T = 60 for 30 min).

Fig. 8

The RGB value of TT pH indicators towards 100 μL from each standard dilutions (mix of components) under accelerated storage conditions (T = 60 °C for 30 min).

Fig. 9

The RGB value of TT pH indicators towards 100 μL from each standard dilutions (mix of components) under specific storage condition (T: 40 °C for 30 min, RH∼ 55%).

Fig. 10

TVB-N, TVC and Pseudomonas growth versus the storage time at 4 °C.

Fig. 11

ΔRGB versus TVB-N gases (a), TVC (b), and pH (c) during fish storage at 4 °C. Correlation between the onset of an increase in microbial population and TVB-N gas release and sensor response (d).