Predicting target release profile of antimicrobials from controlled release packaging

Controlled release packaging (CRP) is an innovative technology that uses the package to deliver active compounds, such as antimicrobials in a controlled manner to enhance food safety and quality. There is an optimum range of release profiles of antimicrobial from CRP, called "Target release profile" that depends on food composition, packaging material, shelf life and temperature, to produce an effective inhibition of microbial growth for the desired shelf life.;The objective of the research is to develop mathematical model to predict target release profile of antimicrobials from CRP. Target release profile is the missing link for advancing research and development in CRP. Quantifying it helps polymer scientists design packages, tailor-made for the food and shelf life requirements for effective inhibition of microorganisms under different stress conditions.;This objective is achieved by quantifying the critical parameters influencing target release profile through a model system based on two hypotheses. The first hypothesis was developed to express target release profile in form of a quantifiable parameter such as diffusivity. The hypothesis was tested by generating release profile based on literature data for potassium sorbate (bacteriostatic antimicrobial) diffusivities and evaluating their effect on the growth of Escherichia coli DH5alpha+/-. The results show that not all release profiles were effective in inhibiting the growth of the organisms. There was an optimum range of release profiles, thereby an optimum range of diffusivities suitable to extend the lag period of E.coli DH5alpha+/- for the 24 hours period tested. Diffusivity between 7.5 x10-12 m2;/s and 2.60x10-13;m2;/s was needed to provide complete inhibition of the microorganism for 24 hours when 0.2 g (1 mg/mL) was added to the polymer. Increasing the amount of antimicrobial in polymer to 0.4 g and 0.6 g increased the effective range. The second hypothesis was developed to quantify the optimum diffusivity based on minimum inhibitory concentration (MIC) of the antimicrobial and its effect on microbial lag period. The hypothesis states that the release rate of antimicrobials from the package during the inherent lag period of the organism must be equal or more than their MIC to produce an effective inhibition of the organism over the desired shelf life. The results supported the hypothesis that a minimum of 0.5 mg/mL has to be delivered during the inherent lag period of E.coli DH5alpha+/-.;The results from the hypotheses were used to develop the target release rate model. The model is simple and takes into account the antimicrobial efficacy (MIC), microbial growth kinetics (lag period) and correlates them with the release kinetics of antimicrobial from polymer (diffusivity). The target release model was validated by evaluating the effect of nisin (bactericidal antimicrobial) release profile on the growth of Micrococcus luteus. The results validated the model and also showed that the predicted release profile was highly effective considering controlled release may use only 15% nisin to achieve complete inhibition of M. luetus rather than instant addition of 100% nisin.