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. 2025 Jun 23;14(13):2200.
doi: 10.3390/foods14132200.

A Hydrophobic Ratiometric Fluorescent Indicator Film Using Electrospinning for Visual Monitoring of Meat Freshness

Xiaodong Zhai  1   2 , Xingdan Ma  1 , Yue Sun  1 , Yuhong Xue  1 , Wanwan Ban  1 , Wenjun Song  1 , Tingting Shen  1 , Zhihua Li  1 , Xiaowei Huang  1 , Qing Sun  1 , Kunlong Wu  2 , Zhilong Chen  2 , Wenwu Zou  2 , Biao Liu  2 , Liang Zhang  2 , Jiaji Zhu  3
Affiliations

A Hydrophobic Ratiometric Fluorescent Indicator Film Using Electrospinning for Visual Monitoring of Meat Freshness

Xiaodong Zhai et al. Foods. .

Abstract

A ratiometric fluorescent film with high gas sensitivity and stability was developed using electrospinning technology for monitoring food spoilage. 5(6)-Carboxyfluorescein (5(6)-FAM) was used as the indicator, combined with the internal reference Rhodamine B (RHB), to establish a composite ratiometric fluorescent probe (FAM@RHB). The hydrophobic fluorescent films were fabricated by incorporating FAM@RHB probes into polyvinylidene fluoride (PVDF) at varying molar ratios through electrospinning. The FR-2 film with a 2:8 ratio of 5(6)-FAM to RHB exhibited the best performance, demonstrating excellent hydrophobicity with a water contact angle (WCA) of 113.45° and good color stability, with a ΔE value of 2.05 after 14 days of storage at 4 °C. Gas sensitivity tests indicated that FR-2 exhibited a limit of detection (LOD) of 0.54 μM for trimethylamine (TMA). In the application of monitoring the freshness of pork and beef at 4 °C, the fluorescence color of the FR-2 film significantly changed from orange-yellow to green, enabling the visual monitoring of meat freshness. Hence, this study provides a new approach for intelligent food packaging.

Keywords: electrospinning; food freshness; hydrophobic; intelligent packaging; ratiometric fluorescent film.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Fluorescence spectra of 5(6)-FAM (A) and RHB (B) at different excitation wavelengths.
Figure 2
Figure 2
Fluorescence spectra (excitation wavelength of 490 nm) of the FAM@RHB probe solution at different volume ratios of FAM–RHB, before and after reacting with TMA (A–E); the F1-F0 of different ratios of fluorescent probes (F): F1 is F516nm/F580nm after the reaction, and F0 is F516nm/F580nm before the reaction.
Figure 3
Figure 3
The UV–Vis absorption spectra of RHB and 5(6)-FAM.
Figure 4
Figure 4
Fluorescence spectra of the FAM@RHB fluorescent probe (2:8) reacting with different concentrations of TMA under 490 nm excitation (A); linear relationship of the FAM@RHB ratiometric fluorescence intensity (F516nm/F580nm) versus TMA concentration (B); the color changes in the FAM@RHB fluorescent probe under daylight (C) and UV light (D) at different TMA concentrations.
Figure 5
Figure 5
SEM images of FR-1, FR-2, FR-3, FR-4, and FR-5 films (A); fiber diameters of FR-1, FR-2, FR-3, FR-4, and FR-5 films (B).
Figure 5
Figure 5
SEM images of FR-1, FR-2, FR-3, FR-4, and FR-5 films (A); fiber diameters of FR-1, FR-2, FR-3, FR-4, and FR-5 films (B).
Figure 6
Figure 6
The WCA images (A) and significance analysis (B) of the pure PVDF film, FR-1 film, FR-2 film, FR-3 film, FR-4 film, and FR-5 film. Different letters in the figure indicate statistically significant differences (p < 0.05).
Figure 7
Figure 7
Confocal fluorescence images of five different films.
Figure 8
Figure 8
FTIR spectra of the FR-2 film.
Figure 9
Figure 9
The fluorescent color changes (A) and color difference value ΔE change (B) in the films stored at 4 °C for 14 days.
Figure 10
Figure 10
The colors of the FR-1, FR-2, FR-3, FR-4, and FR-5 films in response to TMA at different concentrations (A); the plot of the ΔE values of the FR-1, FR-2, FR-3, FR-4, and FR-5 films versus the concentration of TMA (B–F).
Figure 11
Figure 11
The photos of pork and beef packaging containing a FR-2 film under 4 °C under visible light and UV light (A). The relation between ΔE values of the FR-2 film and TVB-N values of pork (B) and beef (C). Correlation analysis of ΔE values of the FR-2 film with TVB-N values of pork (D) and beef (E).
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