The search for the perfect antimicrobial solutions continues

Making the case for antimicrobial packaging films

Photo Neha Deshmuch – Unsplash

As l mentioned in my recent article Making the case for antimicrobial packaging films: Time to get more Active? – the number of research projects developing antimicrobial or antibacterial films is staggering. Industry intel and other reliable sources continue to report regularly as papers are published on new active and intelligent solutions for food packaging.

While l am still of the view that more coordination would benefit the commercialization of these materials, here are just a few of those reported recently, which show promise, many containing chitosan, which was one of the materials, along with cellulose, which l favour.

Scientists at various academic institutions in Shandong, China, have developed modified, biodegradable, active, intelligent food packaging films with lychee shell extract as pH indicator; films monitor fish freshness at 4°C to 25°C and show improved UV blocking and tensile strength. The films are made of gelatin, chitosan and polyvinyl alcohol. This Gel/Csa/PVA/LE film has the pH sensitivity to show an obvious color change (red) at 25 °C in defined time periods. The results suggested it could be applied to intelligent food packaging film to indicate the freshness of fish.

More from China, this time Harbin, where researchers have created intelligent, active food packaging film made from chitosan/chitin nanofibres with eggplant peel anthocyanins. The film indicates pork freshness and durability.

When the content of chitin was 5 wt%, the tensile strength, elongation at break, the water vapour and oxygen barrier properties of the chitosan film were significantly increased. When EE was added to the films, the antibacterial and antioxidant capacities were significantly improved. Chitosan-CN-EE films effectively indicated the freshness of pork during storage.

Still in China, researchers based in Shanghai have developed reusable pH sensor film for intelligent food packaging using waterborne polyurethane (WPU) and azo reactive dye. The film changes colour from red to brown to green between pH 3-10 and shows resistance to leakage. It monitors real-time yogurt freshness, according to a report in NewsRX.

Modified WPUs demonstrated that the thermal stability and mechanical properties of WPU film increased slightly after dye modification. It showed excellent reversibility when pH was varied between 3 and 10. Additionally, the pH sensor films also showed a remarkable resistance to leakage under strong acidic and alkaline solutions. When applied to different kinds of fresh yogurt an obvious colour change was observed.

According to a report in Food & Beverage New (India) the use of nanotechnology for food packaging is set to increase by 15%. Nanomaterials can provide better protection of food, offer improved humidity resistance as well as temperature and gas barrier and sense microbial or biochemical changes, according to the report.

Nano-sensors used in the food packaging sector include electronic noses, nano-particles based sensors, nano-cantilevers, array biosensors, nano-test strips and nanoparticles in solution. Packaging with nano-sensors is helpful to identify internal and external conditions of food and containers throughout the supply chain. Also, in plastic packaging, nano-sensors can detect gases in food when it spoils, so packaging changes colour to alert the consumer.

From Indonesia and Malaysia comes an edible coating technology. Scientists applied an edible coating of chitosan, fish skin gelatin and black tea extract to extend shelf life of fresh-cut papaya. The coating decreased weight loss and maintained texture, as well as maintaining several other chemical parameters, they claim.

The preparation of the edible coating solution was based on chitosan, tuna skin gelatin, glycerol, and black tea with different concentrations of 0% to 15%. The edible coating was then applied to minimally processed papaya fruit and stored for 1, 4, 7, and 10 days to determine the effect on the physical, chemical and microbiological characteristics of the fruit. The results showed that the treatment, with the addition of black tea extract, was able to suppress microbial growth during storage.

Finally, teams at universities based in Seville and Malaga in Spain and Genoa and Ancona in Italy have produced bio-based lacquers prepared from underutilized tomato processing residue such as pomace as sustainable alternatives to bisphenol A (BPA)-based coatings for metal food packaging.

The team tested the coating on various metal containers, in general the best results were found for tomato pomace-based lacquers applied on aluminium. The estimation of the environmental sustainability of the process showed its suitability for circular economy targets. A life cycle analysis (LCA) was applied to the overall process, revealing multiple advantages for both the environment and human health, they say.

This article was created in collaboration with AIPIA (the Active and Intelligent Packaging Industry Association). For a full update on active and intelligent packaging, come along to the AIPIA World Congress (co-organized by Packaging Europe) in Amsterdam on 14-15 November. The only smart packaging event covering the entire technology spectrum, the World Congress is a meeting place for the global active and intelligent packaging industry where brand owners, innovators, and other stakeholders can network and see and discuss the latest trends and innovations. Register to attend here.


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