News Items - International Association of Packaging Research Institutes
Active & Intelligent Packaging: the other type of ‘AI’

As in previous years, this summer’s IAPRI Conference saw several papers dedicated to the area of Active & Intelligent (A&I) packaging, many of them exploring the overlap between these technologies and novel or biobased materials.

One IAPRI member organization with a well-developed focus on these topics is the University of Hasselt (UHasselt) Materials and Packaging Research & Services Centre in Belgium. Here, Mieke Buntinx identifies three aspects to A&I technologies and their current status, from a European perspective.
 
Firstly, she tells IAPRI, there is no shortage of research findings showing that the various A&I systems can have distinct benefits in prolonging shelf-life and limiting food waste. “On the other hand, these new functional materials must be proven safe for humans and the environment, and in addition, they must fit in with the current European dynamic legislation on packaging and packaging waste,” Buntinx explains.
 
“The combination of these three aspects might explain why the market implementation of A&I packaging is relatively slow.”
 
UHasselt’s Chris Vanheusden puts these European realities in a wider global context. “Despite the invested effort and successful introduction of some active packaging concepts in Japan and the USA, a general introduction of these A&I concepts in industry is still limited,” he says. He singles out nanotechnology as showing great promise in this arena but, like Buntinx, highlights concerns about safety and migration limits.
 
“In addition, a lack of awareness and knowledge about A&I packaging, the time-consuming move from lab-scale to industrial scale and a gap between consumer and industry slows down their commercialization,” he says.
 
A new spin on substrates
 
But as the range of Mumbai A&I presentations demonstrated, research is thriving across this wide field. More broadly, as Vanheusden confirms, the active packaging concepts that have had the most impact include scavengers (especially oxygen scavengers), absorbers and emitters – for compounds such as antioxidants.
 
“Trends in intelligent packaging include interactive concepts with printed electronics, such as RFID, or sensors to monitor storage conditions,” he adds.
 
But one area where Vanheusden has seen a significant increase in research publications has been biopolymer nanocomposites, which may improve processing or the material properties, or may add to functionality. This was the area, in fact, where he delivered his own presentation at the Mumbai Conference.
 
In terms of the biopolymer matrix, UHasselt has focused on polyhydroxyalkanoates (PHAs), which are biobased and biodegradable. In his research, Vanheusden looked at the copolymer poly3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx), combining it with zinc oxide (ZnO) nanoparticles. While PHBHHx is known to offer good flexibility and intermediate barrier, ZnO can help to provide UV barrier and antimicrobial activity. “But optimal dispersion of the nanoparticles remains precarious,” he told the Mumbai audience.
 
The research team’s answer was to incorporate the ZnO into the biopolymer by means of centrifugal fiber spinning, subsequently depositing fiber ‘mats’ on top of PHBHHx film substrates. “First, centrifugal fiber spinning of PHBHHx fibers was optimized, before ZnO nanoparticles were added to the chloroform dispersions under controlled conditions,” he reported.
 
“The films show good ZnO dispersion quality,” Vanheusden confirmed. Referring to the different types of UV light, from the shortest wavelength (UVC) to the longest (UVA), he said: “They effectively block UVC, UVB and a major part of the UVA wavelength region, and show suitable hydrophobicity for packaging food products.”
 
The team concluded that this novel method of incorporating ZnO nanoparticles into PHBHHx is “a promising approach for the development of packaging films with an active top layer”.
 
As well as developing new functional bioplastics, says Buntinx, UHasselt’s current research focuses on the potential migration of nanoparticles. She was, for example, the lead author on a Mumbai poster presentation looking at the leaching behavior of silver nanoparticles from PHA-based nanocomposites.
 
Testing titanium dioxide
 
Meanwhile, research at Thailand’s Kasetsart University has revolved around a combination of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) in a biodegradable blend.
Compared with the individual biopolymers, use of a blend leads to better processability and mechanical properties. Here again, research had examined ways of improving visible light and UV barrier, in this case by incorporating titanium dioxide (TiO2) into the blend.
 
But while this UV barrier made the biopolymer blend a good candidate for food packaging applications, offering extended shelf-life for UV-sensitive products, the addition of TiO2 can also alter other types of barrier property. A Mumbai presentation from Kasetsart explored the effects of TiO2 inclusion on both oxygen permeability (OP) and water vapour permeability (WVP).
 
As lead author Uruchaya Sonchaeng explained, TiO2 was combined with the biopolymer matrix in ratios of 1% and 3% by weight. In this case, the polymers were blended in a proportion of 85% PLA/15% PBAT. “The WVP of the PLA/PBAT film decreased by up to 18% when TiO2 was incorporated into the film,” she reported. “However, the OP of the film was not affected by the TiO2.”
 
In terms of measuring hydrophobicity, the contact angle (CA) was shown to decrease when 1% TiO2 was incorporated into the film, but it stayed the same when the proportion of TiO2 was 3%.
 
“Overall, incorporating TiO2 contributed to improved UV-shielding properties, without compromising the barrier properties of the base PLA/PBAT film,” said Sonchaeng. “Further investigation on the morphology of the film samples might contribute to a better understanding of the film properties.”
 
Applications with alginate
 
With the emphasis falling on antimicrobial activity rather than barrier, Switzerland’s ZHAW offered a paper looking at the role of a cinnamon essential oil (CEO) and citric acid mix in sodium alginate film used to extend the shelf-life of packaged ham.
 
Nadine Rüegg presented research showing how the team created a film combining sodium alginate with 6% CEO as a volatile antimicrobial agent and proportions of 4% and 6% of citric acid as a non-volatile antimicrobial. The effectiveness of these antimicrobials was measured through in vitro tests against Escherichia coli (E. coli) and Listeria innocua (L. innocua) by disc diffusion or vapour diffusion assay.
 
Films containing citric acid showed an extensive zone of inhibition in disc diffusion. “Films containing CEO also showed significant antimicrobial activities in vapour diffusion assays that resulted in a log reduction of 5.3 for E. coli and 3.2 for L. innocua after six days,” she said.
 
The antimicrobial activity of all films was also tested on sliced cooked ham. Here, significantly, the films containing CEO did not prevent the growth of L. innocua inoculated on to ham. The films with citric acid, on the other hand, did fully inhibit the growth of L. innocua on ham stored at 7.5degC for 12 days.
 
“The addition of antimicrobial substances in sodium alginate films resulted in a slight – but significant – colour change, and reduced the tensile strength of the films significantly,” Rüegg added.
 
Of course, one answer to current concerns about packaging – and particularly plastics – is to reduce or eliminate it altogether. A paper from Darylle Jerome Ortiz of the Philippines’ Industrial Technology Development Institute, part of the Department of Science and Technology (DOST), reminded the Mumbai audience how some of the same biobased materials can be repurposed in non-packaging applications.
 
In this research project, sodium alginate was used in conjunction with lemongrass essential oil (LEO) as a direct coating on to fresh cut pineapple. Using distilled water, a solution was formed with the alginate in a proportion of 1%, glycerol added (1%) for improved plasticity, and LEO in proportions of 0.3%, 0.2%, 0.1% and 0.05% by weight. Dipping of the pineapple in the sodium alginate solution was followed by crosslinking using a calcium lactate solution.
 
“With the active edible coating applied, the shelf-life of fresh-cut pineapple was extended from 4 up to 8 days – a 100% increase compared to the control sample,” said Ortiz. “The results revealed the effectiveness of the coating in maintaining quality, safety and extending shelf-life.”
 
The same type of active edible coating could be developed and trialled for other types of freshly-cut fruits, he added.
 
 

Published: 08/19/23