A scientific review published on April 27, 2016, in the peer-reviewed journal Food Packaging and Shelf Life focuses on nanoparticles used in nanocomposite materials intended for food packaging. Victor Souza and Ana Fernando from MEtRiCS, Universidade Nova de Lisboa, Portugal, discuss the existing gaps in regard to migration and toxicity of these nanomaterials, but also their influence on the biodegradability of the biopolymer they are incorporated into.
The advantage of many biopolymers (e.g. poly(lactic acid) (PLA), starch, cellulose, chitosan, agar, alginate, proteins) is their biodegradability, i.e. ability to be degraded or even mineralized by microorganisms. On the other hand, important disadvantages are their poor mechanical and barrier properties, which limit their use for many applications, including food packaging. Various nanomaterials can be incorporated into biopolymers, resulting in nanocomposites with significantly improved performance, lower production cost and greater application possibilities. However, the reinforcement of biopolymers by nanoparticles can at the same time affect their biodegradability. Only a few studies have so far evaluated the influence of nanofillers on biodegradability. Contradictory results were obtained, requiring further research; however, slower and reduced biodegradability has been noted more frequently than an improved biodegradability.
The studies on migration of nanoparticles into food have been hampered by the lack of analytical standards and reliable methods for sensitive detection of nanoparticles in food simulants and foodstuffs. Some nanomaterials can be changed through the interaction with food simulants or foods. For example, it was shown that the acidic food simulant (3% acetic acid) causes dissolution of silver nanoparticles, and their subsequent disappearance (FPF reported). However, a study by Ramos and colleagues, published in early 2016 in the peer-reviewed journal Talanta, found that, although the proportion of silver present as nanoparticles was lower in 3% acetic acid than in water, the absolute numbers of silver nanoparticles migrating into water and 3% acetic acid turned out to be similar. This was because with the acidic food simulant, higher amounts of silver had migrated in total. Souza and Fernando note that more research is needed to understand the factors that influence the migration of nanoparticles from nanocomposites, as this might help resolving the conflicting reports, and contribute to risk assessment of these materials.
Similarly, many knowledge gaps exist regarding the toxicity of nanoparticles. The toxicological evaluation is complicated by the fact that interaction with foods may change nanoparticles’ size or morphology – the qualities that are also important determinants of their toxic potential. Furthermore, the influence of functionalization on nanoparticles’ toxicity should be examined more closely in the future. For example, a study by Maisanaba and colleagues from the University of Sevilla, Spain, published in April 2016 in the peer-reviewed journal Chemosphere, has shown that organomodified clay (Clay2) exhibits genotoxic properties and is more cytotoxic in vitro, while the raw clay shows lower toxicity.
The studies evaluating novel nanocomposite materials for applications in food packaging should consider not only their potential migration and toxicity, but also the overall benefits of nanomaterial incorporation, considering the intended use. For example, the trade-offs between the improved mechanical properties and reduced biodegradability should be assessed. For nanomaterials used as antimicrobials, overall improvement in food preservation, or a lack thereof, should be assessed as well. For example, a study by Gallocchio and colleagues from the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), Italy, published on May 5, 2016, in the peer-reviewed journal Food Additives & Contaminants: Part A, showed that the amount of common spoilage microorganisms in chicken meat balls did not differ between samples stored in silver nanoparticle-containing FreshLongerTM Plastic Storage bag (produced in USA) and conventional plastic bag bought in retail in Italy. Careful evaluation of benefits and disadvantages associated with the use of nanomaterials in food packaging may allow avoiding unjustified use and unnecessary impacts on human health and the environment.
Souza, V. G. L., and Fernando, A. L. (2016). “Nanoparticles in food packaging: Biodegradability and potential migration into food – A review.” Food Packaging and Shelf Life 8: 63-70.
Ramos, K., et al. (2016). “Silver speciation and characterization of nanoparticles released from plastic food containers by single particle ICPMS.” Talanta 151: 83-90.
Maisanaba, S., et al. (2016). “Induction of micronuclei and alteration of gene expression by an organomodified clay in HepG2 cells.” Chemosphere 154: 240-248.
Gallocchio, F., et al. (2016). “Testing nano-silver food packaging to evaluate silver migration and food spoilage bacteria on chicken meat.” Food Additives & Contaminants: Part A (published online on May 5, 2016)