*Food Preservation Packaging DOI: http://dx.doi.org/10.5772/intechopen.110043*

packaging to occur and for components of the packaging to be absorbed by, or react with, the food. Food packaging interaction involves mass transfer through which packaging material migrate to food or external environmental factors (such as odor, light or gas) permeate into the packaged food or process that involves sorption through adsorption (by packaging) or absorption (by the food) or combination of all which at end affect the initial quality/integrity of the packaging or the food product. The mass transfer occurs as a result of difference in concentration between the two medium (High and low) which causes migration at a rate equal to the driving force of the specific food component. Different packaging materials allows different mass transfer rate example; metal or glass package approve very low mass transfer if compared with package made up of plastic. The mass movement allows permeation to small molecules of water vapor, volatile gasses, organic vapors, flavors, aroma and additives from food. These movement causes change in the component's concentration gradient as such more molecule migrated with extended storage which causes quality reduction. Exchange of materials in packaging system offers both positive and negative advantage. Depending on packaging type selected, active package react or changes the packaging environment by interacting with the food enclosed (packaged) thereby extending the food shelf life. The molecular exchange in food packaging can either be through; (i) permeation (ii) migration (iii) sorption/scalping and begin from the moment the package contacts the food during production, and extends throughout the package shelf life and can produce adverse effects on the food, and/ or the package. As shown in the **Figure 1** below, food-package interaction follows different pattern (permeation, migration, sorption/scalping) and causes varying degree in quality effect on the food (drying, aroma loss, moisture loss/absorption etc.). Different food components follows different exchange pattern with volatile compound mostly adopting to permeation and very low molecule motile compound (such as water molecule) following a migration and permeation sequence. The whole foodpackaging interaction methods involves three elements/environment viz. (i) External environment (ii) Internal environment (food) (iii) Packaging. In Permeation pattern molecule of moisture, CO2, O2 and other volatile compounds move either from the

**Figure 1.** *Food package interaction. Adapted with modification from [6].* food or from external environment to the internal packaging environment or to the external surrounding environment through the packaging material [6] this may be due to porosity or less intactness of the packaging film. Example, some nylon packaging can allow moisture to pass thereby causing dissolution of the food packaged. In a case of sachet packs, poor sealing may allow rapid permeation (leakage) which may give rise to moisture loss/absorption, drying (dehydration), de-carbonation, offflavors and microbial growth (as in **Figure 1** below). Leakages on sachets foods can be detected by using vacuum leak test apparatus (VLTA). VLTA machines are made in a way that they absorbed all available gasses around the packaging environment thereby given chance to only permeation of gas from the internal packaging environment that can be physically detected through gas bubble formation (when they escape from the internal packaging environment due to pressure surrounding the external environment formed by vacuum creation) as leakages from the sachets. In the testing process, the sachets are first immersed in a water in the vacuum creation section of the machine, pressure level are then set from the program which will be used to create the vacuum. While permeation covers both external and internal environment of the packaging system, migration on the other hands involves movement of packaging materials from the packaging film to the food. Migration reduce the compactness of the packaging film and can give rise to permeation when the surface packaging materials erodes and migrate to the food which then increase the characteristics porosity of the packaging film as such increase rate of components migration, migration causes sensory quality loss, packaging damage and flavor development. Except the food packaging allows, food-package interaction though inevitable but causes very limited effect to the quality of the food enclosed.

#### *1.1.1 Permeation*

Caner [6] defines permeation as the movement of gases, vapors or liquids through homogenous packaging materials, and excludes the passage of materials through perforation, cracks, or other related defects. In his own definition, Caner [6] excluded any internal or external defects that allow passage of molecule through packaging as permeation as such defines it as the characteristics of the package that allow such movement therefore; permeation to his own definition is inherent to the packaging materials used. According to Caner [6] permeation involves molecular movement of volatiles and aroma component of gases, moisture and other low molecular weight substances from the outside (external) environment into the food through the packaging materials or vice versa. Permeation process through a packaging film occurs in a three steps:

1.**Solution or Absorption:** the adsorption involves the dissolution of the food materials on to the surface of the packaging materials. In adsorption process the penetrant disintegrate from the parent food mass and the absorbed to the surface of the packaging. Adsorption process depends on the: (i) particulate nature of the food (ii) condition of the packaging environment e.g. pH, Moisture content, Acidity (iii) the absorptivity of the packaging materials to penetrant. Adsorption principle follows Henry's rule which states that the amount of gas absorbed by a given volume of a liquid at a given temperature is directly proportional to the partial pressure of the gas therefore the absorptivity of the food depends on the pressure of the internal packaging system which depends on the seallability of the package and the relative condition of the food prior to the initial packaging.
