New Hydrogel Indicator with Natural Color to Check Shrimp Freshness

Jim Crocker
15th August, 2024

New Hydrogel Indicator with Natural Color to Check Shrimp Freshness

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Shunde Polytechnic, Foshan, China, developed a robust dual-network colorimetric hydrogel for real-time food freshness detection
  • The hydrogel incorporates modified aramid nanofibers (ANF-SN) to enhance mechanical properties and thermal stability
  • The hydrogel shows excellent color responsiveness to pH changes and ammonia, making it suitable for monitoring shrimp freshness
The need for effective methods to monitor food freshness has become increasingly important to ensure food safety and reduce waste. Traditional methods often rely on chemical tests or electronic sensors, which can be costly and complex. Recent advancements in smart packaging have introduced pH-responsive hydrogels as a promising solution for real-time food freshness detection. However, the fragile mechanical properties of these hydrogels have limited their practical applications. A recent study conducted by researchers at Shunde Polytechnic, Foshan, P. R. China, has addressed this issue by developing a robust dual-network colorimetric hydrogel[1]. The study aimed to enhance the mechanical properties and thermal stability of pH-responsive hydrogels by incorporating aramid nanofibers (ANFs). ANFs are known for their excellent mechanical properties but have limited surface activity. To overcome this limitation, the researchers modified the surface of ANFs using a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3). This treatment, which produced modified ANFs designated as ANF-SN, increased the reactivity and dispersibility of the nanofibers by introducing more active groups on their surface. The researchers chose anthocyanin extract from purple sweet potatoes (PSPE) for its significant color response to pH variations (ranging from 2 to 12) and ammonia vapor. By combining ANF-SN, polyvinyl alcohol/sodium alginate (PVA/SA), and PSPE, they fabricated a stable dual-network colorimetric hydrogel through a two-step method involving freeze-thawing and staining. Characterization analysis revealed that the strong acid modification of ANFs effectively improved their chemical reactivity. ANF-SN outperformed unmodified ANFs in promoting the formation of hydrogen bond networks, enhancing hydrogel network structures, and improving the viscoelasticity of the hydrogels. The optimal hydrogel indicator, PVA/SA/ANF-SN/PSPE, demonstrated excellent color responsiveness and sensitivity to ammonia, making it suitable for real-time monitoring of shrimp freshness. The hydrogel's performance could be further validated using a smartphone and RGB color-picking software. This study builds on previous research in the field of smart packaging. For instance, earlier studies have demonstrated the potential of incorporating anthocyanins into various polymer matrices to create pH-responsive films. One such study developed a smart film using red cabbage anthocyanins (RCAs) immobilized in chitosan/oxidized-chitin nanocrystals composites. This film effectively monitored the freshness of hairtail and shrimp, showing significant color changes correlating with spoilage stages[2]. Another study used purple sweet potato anthocyanins (PSPA) in a carboxymethyl-cellulose/starch film, which also showed color changes from red to blue and green in response to pH variations and ammonia, successfully indicating fish spoilage[3]. The new study by Shunde Polytechnic expands on these findings by addressing the mechanical limitations of previous hydrogel-based indicators. By enhancing the surface properties of ANFs through acid modification, the researchers created a more robust and thermally stable hydrogel. This advancement not only improves the practical applicability of pH-responsive hydrogels but also provides a more reliable method for real-time food freshness detection. In conclusion, the development of the PVA/SA/ANF-SN/PSPE hydrogel represents a significant step forward in the field of intelligent food packaging. By combining the excellent mechanical properties of modified ANFs with the colorimetric sensitivity of PSPE, the researchers have created a durable and effective tool for monitoring food freshness. This innovation has the potential to improve food safety, reduce waste, and provide consumers with a simple and reliable method for assessing the quality of their food.

BiotechMarine Biology

References

Main Study

1) Preparation of a colorimetric hydrogel indicator reinforced with modified aramid nanofiber employing natural anthocyanin to monitor shrimp freshness.

Published 13th August, 2024

https://doi.org/10.1111/1750-3841.17290

Related Studies

2) Fabrication of halochromic smart films by immobilizing red cabbage anthocyanins into chitosan/oxidized-chitin nanocrystals composites for real-time hairtail and shrimp freshness monitoring.

https://doi.org/10.1016/j.ijbiomac.2021.02.170

3) Preparation and characterization of indicator films from carboxymethyl-cellulose/starch and purple sweet potato (Ipomoea batatas (L.) lam) anthocyanins for monitoring fish freshness.

https://doi.org/10.1016/j.ijbiomac.2019.12.024


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