Material Smart
Material Smart Packaging: by Pornpun Theinsathid Country Manager Thailand and Vietnam, Purac Gerrit Gobius du Sart Specialist Polymer Technology, Innovation Center PLA, Purac Figure 1. The use of antimicrobial packaging will result in longer shelf lives for meat products. [1] Jamshidian, M. et al. Poly-Lactic Acid: Production, Applications, Nanocomposites, and Release Studies, Comprehensive Reviews in Food Science and Food Safety 2010, 9, 552-571. [2] Theinsathid, P. et al. Journal of Biobased Materials and Bioenergy 2011, 5, 17-29. [3] Theinsathid, P. et al. Development of innovative biobased active packaging against Listeria monocytogenes, Salmonella Typhimurium, Proceeding of EFFOST Conference - New Challenge in Food Preservation, 11st- 13rd November, 2009, Budapest, Hungary. Research performed in the framework of the “Technopreneurship and Innovation Management” program, Chulalongkorn University, Thailand. You are doing your weekly grocery shopping. Last item on the list: sausages. You walk over to the butcher’s isle, pick the nicest looking frankfurters and notice a number of labels on the packaging material. Who cares about the labels? The sausages look good! Upon closer inspection at home, you notice that one label says that the plastic material consists of polylactic acid (PLA). Being a constant reader of bioplastics MAGAZINE you know the environmental advantages of PLA as to renewable resources and carbon footprint perfectly well. Great, on to the next label. It says something about ‘smart packaging’ and ‘antimicrobial properties’. And indeed, the expiration date isn’t as close by as it used to be with those oldfashioned plastic films. This kind of ‘active packaging’ is no science fiction, but a hot topic in the food packaging industry [1]. The importance of such protection against micro-organisms is underscored by the U.S. government’s regulatory stance on Listeria monocytogenes: zero tolerance. If even the lowest amount of this pathogen is found on a 25-g to 50-g sample of a cooked meat or poultry product, it has to be recalled. Active antibacterial wrapping could result in an extended shelf life for the product. An all too logical choice as an active ingredient in PLA, of course, is lactic acid. The antimicrobial function of lactic acid is well-recognized and applied in many food and feed products as demonstrated in tests in Purac laboratories (Fig 2). Furthermore, it has been shown in numerous studies that films consisting of a PLA-based matrix and antimicrobials such as lactic acid indeed show antimicrobial action. One such study was dedicated to the suitability of environmentally friendly active packaging films, produced by melt extrusion. Lactic acid is well-known for its antimicrobial properties against L. monocytogenes and is already widely applied for meat preservation. As such, this natural antimicrobial was incorporated at three different concentrations into PLA resin. The films were then tested for their antimicrobial activity against L. monocytogenes, and Salmonella Typhimurium using the ASTM E2149-01 method under dynamic contact conditions. Inhibition of L. monocytogenes and S. Typhimurium by the antimicrobial films was clearly observed using agar diffusion assay (Fig 3). Survival of the pathogens was studied by means of bacterial counts after contact times of 0, 6, and 24 h at 37°C. This type of antimicrobial packaging film was highly effective in reduction of 4 log units for L. monocytogenes with respect to the control. 40 bioplastics MAGAZINE [03/11] Vol. 6
Material Smart Industry The industrial realization of aforementioned smart packaging systems however is a challenge. In a recent study, experts in the biobased materials and food industries were interviewed to understand the needs and demands of the stakeholders in these fields [2]. Such market-lead studies are important now that the technology is up to the task. The inquiries were made over the complete spectrum of stakeholders, ranging from researchers, politicians and government representatives to petroleum and biobased industry experts to retailers and meat packaging professionals. Besides the need for a clear understanding of both local and global markets, the stakeholders indicated that they anticipate governmental policy and regulation to play an important role in the adoption of such new technologies in the food industry. Technology transfer factors such as high licensing costs and patent barriers were also indicated to be large factors. In that respect, joint research projects are often a hurdle due to the time required to conclude negotiations between the different partners. One barrier that was also mentioned is the limited amount of PLA manufacturers at present, particularly at the local level. The availability of Purac’s lactides and the lactide partnership program will remove this barrier in the years to come; these partnerships will enable growth of the PLA supply chain, both locally and globally. The development of biobased technologies in the smart packaging industry will be realized through multidimensional innovations. The adaptation of those innovations will however require new insights over the entire value chain. Fresh insights indeed. CFU/gram 8 7 6 5 4 3 2 1 10 25 40 55 70 85 days at 5° C/41°F Figure 2. The growth of L. monocytogenes in Frankfurter sausages is restricted after dipping in lactic acid (green curve) prior to packaging. The blue line represents the control sample. CFU = Colonies Forming Unit www.purac.com Figure 3. Agar diffusion studies showing the effect of lactic acid-based antimicrobial films on the growth of Listeria and Salmonella. Colonies of either pathogen could not be viewed in the clear zone with antimicrobial film while such colonies were formed all over the control plates. Blue arrows indicate areas of bacterial growth. Control L. monocytogenes S. Typhimurium bioplastics MAGAZINE [03/11] Vol. 6 41
