35 Measurement of Packaging Materials Measuring Food Packaging Materials Measurements are important in assessing our food supply for quality, regulatory compliance and safety. From how food feels in our mouths to freedom from unwanted antibiotics and pesticide residues, measurements are what ensure that what we consume is expected and safe. In addition, food safety is a paramount global concern as the level of import and export activity grows and the food supply chain spans the globe. Packaging is an important aspect of the food industry, especially for frozen items. Packaging that is too thin or that is not made of the right materials could lead to “freezer burn”; on the other hand, overprotecting food leads to unnecessary costs. In the past, the standard practice was to over engineer material layers so that they always maintained protective barrier properties. Shelf life is the time after production and packaging that a product remains acceptable under defined environmental conditions, To establish this period of time is nowadays required for every food product, not only for commercial reasons but also for safety reasons, as all foods deteriorate with time. The main causes for these deteriorative processes are as follows: Oxidation processes during which the colour fades and may give way to a brownish appearance, rancid tastes, and odours and the food becomes unacceptable.Measurement of Packaging Materials 653 © Microbiological, which is the consequence of the micro- organisms growth, moulds, bacteria or yeasts, some of them pathogens and dangerous for human beings. Often together with the micro-organisms, new compounds appear that are responsible for the bad odours or off flavours. , @ Water losses, which is the consequence of the aging that affect the texture, hardness, appearance, and the taste. However, although the causes of the limitation of the shelf life were known, the analysis of the macroscopic effects usually is not enough to establish the limits and more and more other parameters are required to establish the end of the shelf life. Besides, the evaluation of the deadline cannot be subjective, just as a global measurement, and analytical procedures are needed to standardize the parameters used for establishing the deadline limits. The 21st century is characterized by globalization. In the food area, this means to have the food packaged, because in these conditions, the transport, storage, logistic, and distribution chain can reach distant markets, and a global commercialization can take place. Foodstuffs themselves cannot stand for long time, and new technologies such as vacuum packaging and modified atmosphere packaging, combined with the use of high barrier materials and active packaging, can extend the shelf life of the food inside the package. Emerging technologies like intelligent packaging are then proposed to show that the packaged food is still good and safe. But the challenge is how to measure the shelf life of food. When developing the packaging material or the packaging system, there are different materials, parameters, and variables to modify and to measure. Figure 1 shows a scheme in which the material, the food, and the internal atmosphere play an important role in the shelf-life definition and testing. Interactions between them as well as absolute measurements have to be carried out to study the shelf life. According to this process and depending on the type of samples that we have, different parameters and different654 Food Packaging Technology Hand Book analytical methods will be used. This chapter deals with the main analytical methods, which can be useful for shelf-life evaluation, taking into account that the main purpose in this task is to have an objective and independent series of methods. Avoiding the subjective and personal skills is the main way to measure the key parameters. There is not an exhaustive list of analytical methods, and only those considered as the most appropriate or most common in this type of studies are referred to. HOW TO MEASURE THE SHELF LIFE 3 Packaging material TESTING 1. The food 2. The internal atmosphere 3. The packaging material H,0 aromas [ Selection of parameters | Uy ry /e and selective analytical procedures Internal atmosphere Requirements : Very sen: Fig. 1 Scheme of the food packaging to measure the shelf life As Figure 1 shows, the food, internal atmosphere, and packaging material should be tested to establish the shelf life. The food qualities have to remain constant and be as good as possible and the most similar to the fresh food or just-made food. These qualities involve colour, taste, hardness, texture, volatile compounds, odour, water content, chemical contaminants, absence of microbiological contamination, and freshness, among others. The internal atmosphere means the analysis of gases such as oxygen, carbon dioxide, and other permanent gases and vapours, such as water, volatile compounds transferred by the packaging material, or those released by the food.Measurement of Packaging Materials 655 Finally, the packaging material, which involves the testing of the permeability properties, the analysis of likely contaminants as potential migrants, the migration tests to ensure that the material is safe for being in contact with the food, and the sorption properties of the material to guarantee that the material does not affect the quality of food, by scalping aromas or by trapping the compounds responsible for the colour, flavour, or other food attributes. Inall cases, the first key point is the selection of the parameters to be measured in a quantitative manner for the shelf-life studies, and the second point is the selection of the analytical technique and the procedure to measure the changes, if any, in the whole system. Package testing Package testing or packaging testing involves the measurement of a characteristic or property involved with packaging. This includes packaging materials, packaging components, primary packages, shipping containers, and unit loads, as well as the associated processes. Testing measures the effects and interactions of the levels of packaging, the package contents, external forces, and end-use. It can involve controlled laboratory experiments, subjective evaluations by people, or field testing. Documentation is important: formal test method, test report, photographs, video, etc. Testing can be a qualitative or quantitative procedure. Package testing is often a physical test. With some types of packaging such as food and pharmaceuticals, chemical tests are conducted to determine suitability of food contact materials. Testing programs range from simple tests with little replication to more thorough experimental designs. Package testing can extend for the full life cycle. Packages can be tested for their ability to be recycled and their ability to degrade as surface litter, in a sealed landfill or under composting conditions.656 Food Packaging Technology Hand Book Purpose of packaging testing Packaging testing might have a variety of purposes, such as: @ Determine if, or verify that, the requirements of a specification, regulation, or contract are met © Decide if a new product development program is on track: Demonstrate proof of concept Provide standard data for other scientific, engineering, and quality assurance functions Validate suitability for end-use @ Provide a basis for technical communication ¢ Provide a technical means of comparison of several options @ Provide evidence in legal proceedings: product liability, patents, product claims, etc. ¢ Help solve problems with current packaging ¢ Help identify potential cost savings in packaging Packaging tests can be used for: @ Subjecting packages (and contents) to stresses and dynamics found in the field @ Reproducing the types of damage to packages and contents found in actual shipments Controlling the uniformity of production of packages or components Foods categories such as fresh produce, frozen foods, irradiated foods, fresh fish, canned foods, etc have regulatory requirements and special packaging needs. Package testing often relates to: © Food safety Compatibility of the package with the food Migration of material from the packaging to the foodMeasurement of Packaging Materials 657 @ Shelf life ¢ Barrier properties, porosity, package atmosphere, etc Special quality assurance needs, good manufacturing practices, HACCP, validation protocols, etc Package Insulation Many packages are used for products that are sensitive to temperature. The ability of insulated shipping containers to protect their contents from exposure to temperature fluctuations can be measured in a laboratory. The testing can be of empty containers or of full containers with appropriate jell or ice packs, contents, etc. Ovens, freezers, and environmental chambers are commonly used for this and other types of packaging. Digital data loggers are used to measure temperatures experienced in different distribution systems. This data is sometimes used to develop unique test methods for that distribution system. Determination of Moisture and Total Solids Moisture content is one of the most commonly measured properties of food materials. It is important to food scientists for a number of different reasons: © Legal and Labelling Requirements: There are legal limits to the maximum or minimum amount of water that must be present in certain types of food. ¢ Economic: The cost of many foods depends on the amount of water they contain - water is an inexpensive ingredient, and manufacturers often try to incorporate as much as possible in a food, without exceeding some maximum legal requirement. Microbial Stability: The propensity of microorganisms to grow in foods depends on their water content, For this reason many foods are dried below some critical moisture content.658 Food Packaging Technology Hand Book @ Food Quality: The texture, taste, appearance and stability of foods depend on the amount of water they contain. @ Food Processing Operations: knowledge of the moisture content is often necessary to predict the behaviour of foods during processing, e.g. mixing, drying, flow through a pipe or packaging. Itis therefore important for food scientists to be able to reliably measure moisture contents. A number of analytical techniques have been developed for this purpose, which vary in their accuracy, cost, speed, sensitivity, specificity, ease of operation, etc. The choice of an analytical procedure for a particular application depends on the nature of the food being analyzed and the reason the information is needed. CO, sorption measurement of materials used in food packaging The development of advanced packaging materials for the food industry relies on precise and efficient materials characterization capabilities. For the food industry a precise knowledge of CO, sorption properties by the packaging is particularly important for product quality for the development of plastics and coatings for bottles, and for fundamental understanding of absorption and diffusion properties. In this application the interest was the precise determination of CO, gas sorption properties of the well known packaging material, polyethylene terephthalate (PET). The PCTPro-E&E was used to measure a series of sorption isotherm on amorphous and crystalline PET.