October 1, 2020 – 
The global population is expected to reach 10 billion by 2050, and there is an urgent need to find ways to provide the global populace with safe and nutritious food, while at the same time minimizing the significant impact on the environment. The WHO estimates that microbial contamination causes 584 million foodborne illnesses and 347,000 deaths annually around the world. One of the most efficient ways to reduce food spoilage and waste and to prevent foodborne disease outbreaks is to develop efficient food packaging materials. Synthetic non-biodegradable polymers such as polyethylene terephthalate (PET) and polyethylene (PE) are widely used as a film for food packaging due to their low cost and useful mechanical and gas barrier properties. However, the use of synthetic non-biodegradable polymers has led to the so-called “micro-nano plastics crisis”, which is an emerging issue of major environmental health concern.
Currently, most of the packaging is passive, providing only an inert barrier to the external environment. The concept of active packaging has recently emerged aiming to improve safety and quality of food, not only by protecting the contents from degradation due to oxygen, water vapor, etc., but also by incorporating antimicrobial agents into the package. An approach for producing antimicrobial active packaging materials is the incorporation of antimicrobial agents into the films. However, the main issue of the film-based materials is the low surface-to-volume ratio which requires high quantities of antimicrobial agents for achieving satisfactory antimicrobial effects. This may result in negative sensory effects on the food. In contrast, the most important advantage of fibers over polymeric films is their high surface-to-volume ratio. This enables almost all antimicrobial agents to be on the surface, especially if the diameter of fibers is in the nanoscale (< 100 nm). However, synthesis of most electrospun fibers used in food packaging materials is not “green” since harsh organic solvents are typically used, and high quantity of essential oils per surface area are widely used to provide satisfactory and broad antimicrobial efficacy which may cause negative effects on the organoleptic properties of food.
Researchers at the Center for Nanotechnology and Nanotoxicology at the Harvard T.H. Chan School of Public Health (HCSPH) (www.hsph.harvard.edu/nano ) led by Professor Philip Demokritou have recently been working on development of biopolymer-based platforms for designing antimicrobial food packaging materials enhancing food safety and quality as part of the Harvard-Nanyang Technological University/Singapore Sustainable Nanotechnology Initiative (https://healthtech.ntu.edu.sg/Research/CollaborationProgrammes/NTU-HSPH%20Initiative%20for%20Sustainable%20Nanotechnology/Pages/Home.aspx).
In this study just published at ACS Sustainable Chemistry and Engineering journal, researchers from HCSPH developed one-step and scalable green synthesis approach to engineer antimicrobial fibers from zein, a protein extracted from corn, and a cocktail of nature-derived antimicrobials such as thyme oil, citric acid, and nisin. The ability of the cocktail to inactivate a broad-spectrum of food-related pathogens was demonstrated. The antimicrobial fibers effectively reduced food pathogens such as E. coli and L. innocua populations by ∼5 logs for after 24 hours and 1 hour of exposure, respectively.
Dr Zeynep Aytac, a post-doctoral fellow and the lead author of the study remarked, “We synthesized these antimicrobial zein nanofibers by a green synthesis approach using nontoxic organic solvents and a cocktail of nature-derived antimicrobials, which are all FDA-classified Generally Recognized as Safe (GRAS) for food use. We need to develop more biodegradable and safe to use materials for food package applications.”
Dr. Philip Demokritou, the center Director concluded that “Food systems are one of the strongest human and planetary health determinants and we need to develop new transformative materials to enhance food safety and quality. The emerging micro-nanoplastic environmental crisis makes it imperative to develop nature derived polymers to replace the synthetic polymers and reduce the environmental footprint of packaging materials.”
The ACS Sustainable Chemistry and Engineering publication can be accessed here (https://pubs.acs.org/doi/full/10.1021/acssuschemeng.0c05917). For more information on this and other nano-related research at the Harvard T.H. Chan School of Public Health, please visit our website at www.hsph.harvard.edu/nano.
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