Development, Characterization and Application of a Three-Layer Intelligent pH-Sensing Indicator Based on Bromocresol Green (BCG) for Monitoring Fish Freshness

• Published in: Journal of Ocean University of China 2023-04, Vol.22 (2), p.565-575
• Main Authors: Wen, Haiying, Ou, Changrong, Tang, Haiqing, Sang, Shangyuan, Du, Yingqi, Chen, Jingyi
• Format: Article
• Language: English
• Subjects: Color; Colour; Dyes; Earth and Environmental Science; Earth Sciences; Filter paper; Fish; Food quality; Freshness; Hydrophobicity; Marine fish; Marine fishes; Membrane permeability; Membranes; Meteorology; Migrations; Moisture; Moisture effects; Moisture resistance; Monitoring; Novel foods; Oceanography; Permeability; pH effects; Polytetrafluoroethylene; Safety; Salmon; Sea bass; Shelf life; Stability; Storage; Trimethylamine; Whitefish
• ISSN: 1672-5182; 1993-5021; 1672-5174
• DOI: 10.1007/s11802-023-5326-x

As a novel food quality monitoring technology, intelligent freshness indicator has received wide attention in recent years. However, its poor safety and stability are the main problems hindering its practical application. Hence a new pH-sensing indicator based on bromocresol green (BCG) was developed in this study for nondestructive and real-time monitoring the freshness of marine fishes. The indicator was designed with a three-layer structure, using the polytetrafluoroethylene (PTFE) membrane with high hydrophobicity and air permeability as the inner layer to isolate the moisture in the package, BCG-coated filter paper as the color-changing layer to indicate the freshness of fish, and a transparent unidirectional permeable (TUP) membrane with moisture resistance as the out layer to isolate the moisture in the environment. This contributed to weaken the influence of humidity and prevent dye migration, so as to improve the accuracy and safety of the indicator. Therefore, a highly sensitive and distinguished color variation response to trimethylamine (TMA) standard solution with different concentrations was observed on the indicator. Additionally, the indicator showed a high color stability at different storage temperatures up to 14 days with total color differences (Δ E ) less than 5.0. The indicator presented visible color variations from yellow to green then eventually to blue when applied to monitor the freshness of sea bass and salmon stored at 4°C, implying that fish was spoiled. Meanwhile, indicators Δ E value was significantly positively correlated with total volatile basic nitrogen (TVB-N) and total viable count (TVC) in sea bass and salmon samples. Thus, the pH-sensing indicator can be applied as a cost-effective and promising intelligent indicator for monitoring fish freshness.