Food preservation is done to ensure that baterial and other toxin growth are greatly minimized. Two strategies are generally adopted to achieve this.
Generally, food preservation can be implemented via:
How each food product gets packaged, and what packaging materials are used depends on the method used to preserve food. With respect to dry food, once sufficient water has been removed from the original product, the food must be kept in packages that do not allow moisture to get back into the food item. Dry foods are susceptible to continuing chemical reactions especially if exposed to light and moisture - the chosen packaging barrier (be it high grade PVC or other forms of flexible plastic) must ensure that these reactions are slowed down so that the product shelf life can be maximized.