Active packaging developments using nano-technologies, particularly, are set to increase the shelf life of baked goods significantly. Here is a look at one particular project helping to achieve these targets.
Can new packaging technologies extend the shelf life and condition of baked goods? The short answer to that is, of course, yes. But that does not overcome the general concern of most consumers as to whether they should be packaged in the first place. As we all know, few stop to ask why we put cakes in a semi-rigid tray and then a wrapper or bread (mostly) in plastic bags.
So the challenge presented to the NanoPack project was not only to come up with new flexible packaging materials for food (including materials widely used in baked goods), which greatly extends the shelf life of the products they are designed to wrap, but also to convince the consumers about the benefits. In addition, the scope of the materials’ effectiveness is expected to cover more than just bakery items, but also include produce, proteins and dairy. A further challenge is the objective to use natural products, in this case naturally derived essential oils to achieve the desired effect.
Partners and Objectives
A Horizon 2020 funded scheme NanoPack started in 2017 as a three-year project involving 18 partners, which includes Pão de Gimonde – a Portuguese SME bakery located in Gimonde in northeast Portugal. The enterprise is owned by Manuel António Ferreira and his family, producing artisan handmade bread. The bread is still baked in firewood ovens, following old recipes and forms of production. Its role in the NanoPack project is pilot testing of the packaging of bakery products, to enable assessment of improvements in shelf life under actual production conditions. Other project partners – Arla Group (dairy) and Dawn Meats (proteins) – were tasked to test for their sectors.
While the co-ordinators are an Israeli-based Institute of Technology, Technion, much of the initial development and scientific research was carried out at the Fraunhofer Institute in Germany, working closely with the European Federation of Food Science and Technology (EFFoST), Aarhus University MAPP Centre in Denmark and Ctic Cita, a technology center in La Rioja, Spain. Another major objective for NanoPack is to produce a commercially marketable flexible packaging film, so partners from the converting sector and masterbatch producers are also closely involved. Tests for scaleable production have been undertaken by Constantia Flexibles in Austria, the Bio Base Pilot Plant in Belgium and Tommen Gram in Norway, while Carmel Olefins in Israel are responsible for the production of commercial quantities of raw materials.
NanoPack has explored the use of small clay particles, called halloysite nanotubes (HNTs) for mass-scale industrial food packaging applications. HNTs are considered to be one of the most promising natural nanomaterials. Their unique combination of properties includes a tubular structure, high aspect ratio, low cost and abundant availability, good biocompatibility and high mechanical strength. Their potential to serve as nanoscale containers for encapsulation of antimicrobial molecules has, until now, only been investigated on the laboratory scale. The surfaces of the HNTs are being chemically modified to allow efficient loading and controlled release of natural essential oils. These essential oils are natural substances derived from plants, are generally recognized as safe and show antimicrobial activity against a wide range of microorganisms, including bacteria, yeast, and molds, so highly relevant for baked goods. Plus, they are commercially available at low cost and already approved as a flavoring component. They can be used as high-effective alternatives to existing synthetic food preservatives.
Tests and Trials
Carvacrol, the active component of Oregano, has proved to be the most versatile essential oil during the many tests undertaken across the broad range of products, although others have been, and continue to be tested, such as thyme. Many critical factors have to be taken into account when developing a film of this type. Primarily, the questions are: can an antimicrobial food packaging film encapsulating these particular nanotubes be produced at scale; in a clarity acceptable to converters and consumers; without any side issues such as taint or odor; whilst meeting the very stringent food contact materials regulations existing inside the European Union and other major markets?
Initially, the converters found that producing at normal production speeds and temperatures produced some dissolution of the essential oil concentrations in the polymer mixes, so a certain amount of trial and error on the temperature had to take place, as the efficacy of the antimicrobial effect depends on concentration levels. Again, there were also some odor issues in the beginning, as the concentrations were tested at various levels to see what the most effective ‘range’ might be. This is, of course, complicated by the fact that the material is intended for use not only on baked goods. It quickly became clear that a ‘one size fits’ all solution would not be possible, so the research partners have been looking at the most effective combinations across the different products to be packaged. This has been the major focus of the last months of development. Most pleasing is that the odor issues have largely been solved and the ability to produce a film in industrial volumes proven.
The first trials were performed on bread in 2018, specifically, on a bread recipe from Pão de Gimonde (wheat-bread loaves of 300g with 60% hydration), produced at Ctic Cita’s pilot facility. Tests were made both for inoculated (stored at an ambient temperature of 20°C) and for non-inoculated bread. Mold growth on the surface of the bread was recorded daily to determine shelf life. On the inoculated bread, mold was visible on loaves packed with a control film within 8 days, compared to the ones packed in NanoPack film, which showed mold only 11 days after the inoculation. This represents a 3-day increase in shelf life. With regard to non-inoculated bread, mold was visible after 8 days, when the control film was used, and after 15 days when NanoPack film was used, a 7-day increase in shelf life.
Recently more tests took place on a variety of products using the latest versions of NanoPack films. Notably, the shelf life of cherries, notoriously difficult to keep over even short periods, was extended by 40%, in comparison to those packed in conventional plastics packaging. But, for bread and baked products, the results were even more dramatic, doubling the shelf life of some. Importantly the samples from Pão de Gimonde have no preservatives added. Specifically for baked products, NanoPack’s solution is aimed at replacing added preservatives and be used with or without modiﬁed atmosphere conditions. “We are experimenting with a wide range of products – fresh produce, breads, and pastries, as well as dairy and meat proteins. This means we must identify the best combination and concentration of essential oils as well as the most appropriate packaging format for each,” explained Elisa Valderrama García from the NanoPack scientific team.
Andrew Manly is communication director at the Active & Intelligent Packaging Industry Association (AIPIA)