RESEARCH ARTICLE Comparing Optimum Barrier Variables of Aluminium and MPET Foil Based Laminates for Coffee Packaging Abhishek Dutta Dr. Gautam Dutta Asian Institute of Technology Indian Institute of Foreign Trade [email protected] [email protected] ABSTRACT The barrier property variables for Aluminum based laminates, both under flexed and un-flexed condition, were compared with that of MPET based laminates in order to understand comparative suitability of the later for coffee packaging. Keeping the expected shelf life condition of 180 days the different barrier property variables of the sample MPET and Aluminum based laminates, at the optimality condition, were found out. At the optimum condition, Oxygen transfer rate (OTR) under flexed condition is marginally more for MPET based laminates. However, Aluminium laminates in flexed condition allowing moisture transfer (WVTR) at the rate 24.32 percent stronger than MPET based laminates which may not be good for coffee packaging. KEY WORDS Metalized BOPET, Barrier property, Oxygen Transfer Rate, Water Vapor Transfer Rate, Pinholes 1.0 INTRODUCTION of products requiring higher barrier properties like coffee [1]. In particular, therefore, the packaging Metalized BOPET (Bi-axially oriented polyeth- materials for Coffee need to have high barrier prop- ylene terephthalate) or simply MPET has been in erties which can keep oxygen and water vapor out the limelight now-a-days because the end users find to preserve the freshness of the product inside. Poor them economical as well as environmentally viable barrier property of the packaging material shortens alternative to other forms of packaging material used the shelf life of the packaged product and hence for beverage , food etc. Earlier, exclusive PET (Poly- products like Coffee cannot be packaged by PET propylene and polyethylene terephthalate) based containers known to have weak barrier property [2]. laminates were proved to have poor barrier proper- Therefore, the most widely adopted practice ties and hence considered not suitable for packaging has been to use aluminum foil or other composite Journal of Applied Packaging Research 52 material laminated with Polyester and Polypropyl- MPET structure and Aluminum foil structure for ene film as functional barrier materials to increase packaging purpose. barrier property of packaging material and then use for Coffee packaging. However, the aluminum 2.0 LITERATURE REVIEW foil packaging material needs lots of energy con- sumption in the production process [3]. Alterna- In order to proceed with the objective of the tively, the improved barrier properties of MPET paper, it is important to understand the compo- film have attracted many marketers and hence nents associated with increasing or decreasing of they have shown inclination for replacing Alumin- barrier properties of packaging material. Hence, ium in packaging lamination. The great lustrous we resorted to an extensive literature review on the looks of the MPET in the showcase condition in the subject understudy as discussed below. market place also attracted consumers towards this The concept of shelf life is directly related with product which is in addition to the attraction result- food packaging. It actually indicates the length ing from better barrier properties. However, there is of time that the packaged perishable items would an absolute requirement to compare the barrier pro- get before they are considered unsuitable for sale, prieties of Aluminium and MPET foil based lami- use, or consumption [6]. Product such as coffee is nates at the optimality level to develop clear under- extremely oxygen sensitive, therefore, this product standing in terms of their superiority in providing is required to pack with such packaging materials the best level of freshness to a product like coffee in which have high barrier properties to maintain or the packaged condition. enhance the product’s freshness and shelf life. On the other hand, the perishable products and their 1.1 Purpose of the Paper shelf life depend on the surrounding environment Understanding the barrier properties of the that prevails under packaged condition [7]. Any packaging material is very important from a tech- experiment to increase the shelf life of perishable nological as well as commercial point of view [4]. products, therefore, starts with attempt to control the The most common barrier property spoilers are environment inside the package. Controllability of associated with water vapour and oxygen transfer moisture content, oxygen transfer rate and carbon in a packaging material [5]. These reduce the effec- dioxide exchange rate is of utmost importance when tiveness of packaging material used for protect- the producers or the marketers think of increasing ing and enhancing the product’s commercial value. the shelf life of such products by arresting naturally This paper, therefore, intends to find the optimum happening deterioration process. barrier property variables like water vapour, oxygen Knowledge of the gas transmission properties transfer etc. in a MPET based laminate and compare of packaging materials is critical for a successful the same with the Aluminum based laminate. This package design. Oxygen transmission rate (OTR) will, in a way, allow greater understanding the is one of the most important of the gas transmis- optimum values of the different barriers variables sion properties [8]. OTR is the amount of O2 that under expected shelf life condition in comparative can permeate through a given amount of area with terms between MPET structure and Aluminum foil pressure within a certain time frame. Any attempt structure. Most importantly this will also allow the to increase the shelf life of Coffee, controllability of marketer of products like coffee, requiring high oxygen transfer rate is of utmost importance when barrier properties, to judiciously select between the producers or the marketers think of increasing Comparing Optimum Barrier Variables 53 the shelf life of such products. Packaging solution one (laboratory condition). At the same time more can provide best service to increase the shelf life of Pinholes indicate poor barrier property of the film. the product inside it by setting a balance between So, in a nutshell, a packaging material for Coffee the declining oxygen content and increasing carbon requires low OTR, WVTR, and Pinholes to provide dioxide level inside the package. The oxygen higher shelf life. transfer rate (OTR) is a continuous process and can be assessed by measuring the amount of oxygen 3.0 METHODOLOGY permeates at a normal rate through the package over a period of time [9]. The unit used for measuring the The objective of the paper is to find the optimum oxygen transfer rate (OTR) is cc/m²/24 hours. This barrier property variables like water vapour, oxygen rate of OTR, therefore, is very important to calcu- transfer etc in a MPET based laminate and compare late for the packaging material to understand the the same with the Aluminum based laminate. capability and usability of the material in a particu- Hence, to proceed in determining optimum barrier lar condition. As per industry standard a packaging variables for MPET and Aluminum film laminates, film is considered to high OTR resistant if the OTR 51 samples of MPET (flexed) and aluminum (flexed) rate has a range of approximately 1-10 cc/m²/24 laminates were collected from local markets to hours. A not so high resistant packaging martial test their barrier property in laboratory condition. may clock an OTR rate of approximately 1,000 cc/ Un-flexed MPET and Aluminum laminate samples m²/24 hours. However, a low OTR resistant pack- were collected from different plastic film manufac- aging material can have OTR rate of even 10,000 turing factories. cc/m²/24 hours. Out of the 51 samples collected, 10 random Water vapor transmission rate or simply WVTR samples were subjected to Delamination test in is another important barrier property of plastic laboratory through which layers were removed packaging material which can affect the shelf life of from another using ethyl alcohol solution. This was the product. WVTR indicates the passage of water carried out to understand the structure of the MPET vapor through the packaging material. There are based laminates as well as Aluminum based lami- many food products like Coffee where water vapor nates. The process started with dipping the MPET control is critical. So, such water vapor sensitive laminates in ethanol solution for about an hour. The foods products are required to put inside requisite delaminating of aluminum foil from the laminate high barrier packaging material to achieve desired was a much more time taking job. As there was shelf life [10]. Another important barrier related paucity of available laboratory time so we restricted properties of packaging material are the Pinholes or number of samples to be delaminated to ten randomly simply the strains present and formed in PET films. selected samples laminates only. After delamina- Pinholes describe small areas that at first sight appear tion process it was evident that the MPET based to have no metal coating present. It was reported and Aluminum based laminates structure, used that coating defects such as Pinholes routinely occur for food packaging, typically consisted of several in vacuum-deposited thin films. The less number of functional layers as shown in table 1. MPET based Pinholes present in packaging material determines structure had a 12 micron printed PET, 15 micron good barrier function and hence increased shelf extruded PE, 12 micron MPET, 15 micron sealant life [11]. Expectedly, in the flexed condition, the PET and 30 micron PET and each of these layers had number of P in holes will be more than the un-flexed a functional role to play while performing as food Journal of Applied Packaging Research 54 packaging material. For example, the 12 micron This delamination process allowed us to under- printed PET allows printing to take place smoothly stand the detailed structure of the MPET and on it when put to use by the marketers for branding Aluminum based film commonly used as packag- etc.