DescriptionControlled release packaging is a technology for producing a new generation of packaging materials which can release active compounds such as antioxidants or antimicrobials in a controlled manner to enhance food safety and quality. The objective of this research is to develop a new concept called “target release rate”, which is the rate of releasing active compounds to achieve desirable results. The target release rate is a critical but a missing link for advancing this technology.
The first task was to define the target release rate in a meaningful way. A syringe pump was used to release tocopherol (a natural antioxidant) into linoleic acid (a food simulant) at various rates and temperatures. Methodologies were then developed to define the target release rates based on the degradation of tocopherol (measured by high pressure liquid chromatography) and induction periods of lipid oxidation of linoleic acid (measured by UV spectrophotometer and gas chromatography). Results showed that the target release rate of tocopherol was temperature dependent, around 40, 80 and 150 ppm per day at 30, 40 and 50°C, respectively.
The second task was to study the release rates of tocopherol from polymeric packaging films. Polyethylene/polypropylene polymer blended films containing tocopherol were produced by using the cast film and blown film processes. Tocopherol release rates, degradation of tocopherol, and lipid oxidation of linoleic acid were measured as the functions of time and temperature. Increasing the polypropylene ratio in the film retarded the release of tocopherol from the film but increased the induction period of lipid oxidation. The results confirmed the observation from the syringe pump experiment that degradation of tocopherol and induction period was dependent of the release rate of tocopherol. They also suggested that the release behavior of tocopherol might be manipulated by varying the polymer composition and processing conditions, with the aim of matching the desirable target release rate.
Research was done to test real food, and to characterize physical properties of polymer films. Sesamol released from films increased shelf life of cereal up to 50% longer than the control. Release of tocopherol from film reduced browning of cheese spread.