# Chitosan Electrospun Membranes Possess Natural pH-Responsive Indicators for Smart Real-Time Spoilage Detection of Shrimp

## TL;DR

This paper introduces a smart chitosan membrane that changes color in real-time to detect shrimp spoilage, offering a quick and visual way to monitor freshness.

## Contribution

The novel contribution is the development of a pH-responsive membrane using chitosan and anthocyanins for rapid, real-time spoilage detection in shrimp.

## Key findings

- HACC/PVA-BA membranes with a 1:4 ratio showed rapid pH-response within 5 seconds and strong radical scavenging capacity.
- The membranes achieved up to 64.9% inhibition of E. coli and 62.2% inhibition of S. aureus.
- Color changes in the membranes correlated well with spoilage indicators like TVBN, TPC, and pH during shrimp storage.

## Abstract

Ensuring the simple, rapid, and real-time monitoring of the freshness of fresh food items is essential for maintaining food safety. By reacting with characteristic substances generated during spoilage, pH-responsive indicators can effectively reveal the degree of food freshness. In this study, a mixture of hydroxypropyltrimethyl ammonium chloride chitosan (HACC), polyvinyl alcohol (PVA), and blueberry anthocyanins (BAs) was adopted and, via an electrospinning strategy, changed into a membrane coupled with a pH-responsive ability to assess the freshness of shrimp. The results showed that HACC/PVA-BA membranes with a HACC: PVA ratio of 1:4 exhibited enhanced hydrophobicity, better WVP properties (4.32 × 10−9 g m−1 s−1 Pa−1), a rapid pH-response ability within 5 s and super radical scavenging capacity (56.34% for DPPH and 54.74% for ABTS radicals). HACC’s immutable positive charge creates a strong electrostatic field that pre-concentrates spoilage-generated ammonia and intensifies the protonation state of BAs, which dramatically enhances colorimetric sensitivity and rapid response to volatile amines. Moreover, a satisfactory antibacterial ability for S. aureus and E. coli were also evidenced: HACC/PVA-BA (1:4) membranes achieved a maximum inhibition rate of 64.9% for E. coli and 62.2% for S. aureus. Once applied to monitor the freshness of shrimp stored at 4 °C, the HACC/PVA-BA (1:4) membranes were able to indicate shrimp freshness through visually recognizable color changes within 3 h, which correlated strongly with the spoilage indicators of total volatile basic nitrogen, total viable count, and pH value. It is suggested that the intelligent pH-responsive membranes show great potential for practical application in monitoring food freshness.