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Ran R, Wang L, Su Y, He S, He B, Li C, Wang C, Liu Y, Chen S. Preparation of pH-indicator films based on soy protein isolate/bromothymol blue and methyl red for monitoring fresh-cut apple freshness. J Food Sci 2021; 86:4594-4610. [PMID: 34392537 DOI: 10.1111/1750-3841.15884] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/26/2021] [Accepted: 07/22/2021] [Indexed: 01/17/2023]
Abstract
Intelligent pH-indicator films based on soy protein isolate (SPI) were prepared using pH-sensitive dyes (bromothymol blue and methyl red). The addition of mixed indicators imparts pH-indicator films with an appreciable microstructure, acceptable water resistance, and favorable optical properties. The incorporation of the mixed indicators did not lead to significant improvement in the mechanical properties of films due to weak ionic cross-linking by hydrogen bonding between the SPI macromolecules and low-molecular-weight indicators. Fourier-transform infrared spectroscopy indicated hydrogen bond-mediated intermolecular interactions, and scanning electron microscopy showed that BB/MR were well dispersed in the SPI film. The indicator addition hindered the sorption and passage of water molecules. The water vapor permeability, moisture sorption, moisture content, and total soluble matter were 4.32 to 6.12 ×10-12 g·cm/cm2 ·s·Pa, 36.70% to 73.33%, 25.28% to 44.11%, and 8.21% to 25.56%, respectively. Also, the addition of indicators reduced UV light transmittance with minimal effect on the transparency of the film. The presence of indicators enhanced the pH sensitivity, seen as a visible color reaction at different pHs (total color difference, ΔE > 5). When the pH-indicator film containing 8 ml/100 ml final film emulsions was used to monitor the fresh-cut apple freshness, a green color for fresh status was observed, which turned blue after 60 h. Collectively, our findings suggested that indicator-containing SPI films have the potential for monitoring the freshness of fruits. PRACTICAL APPLICATION: pH-indicator films can help consumers to identify the freshness of packaged food by a change in the color of the packaging material, which is easily visible to the unaided eye without the need for opening the packaging. This protects consumers' interests.
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Affiliation(s)
- Ruimin Ran
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Luyao Wang
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Yuhang Su
- School of Ocean Science and Biochemistry Engineering, Fujian Normal University Fuqing Branch, Fujian Province, Fuzhou, China
| | - Shujian He
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Binbin He
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Cheng Li
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Caixia Wang
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Yuntao Liu
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
| | - Saiyan Chen
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan Province, China
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Jung J, Kasi G, Seo J. Development of functional antimicrobial papers using chitosan/starch-silver nanoparticles. Int J Biol Macromol 2018; 112:530-536. [DOI: 10.1016/j.ijbiomac.2018.01.155] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 01/15/2018] [Accepted: 01/23/2018] [Indexed: 12/11/2022]
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