Development of controlled release antimicrobial films from low methoxyl pectin

Biopolymer-based controlled release antimicrobial packaging is an innovative packaging that aids in controlled replenishment of antimicrobial compound at the food surface, where it is required the most. Various biopolymers have been evaluated for controlled release purposes; focus being mainly on their antimicrobial effectiveness. However, low methoxyl pectin, with the potential to control release of active compounds by forming different degrees of crosslinking, has not been exploited in antimicrobial packaging and there is a lack of understanding of different variables affecting the release properties of active compounds from pectin films. The main objective of this thesis was to identify the key variables involved in the development of pectin-based antimicrobial films by evaluation of the effect of different variables such as composition variables (size of active compound and degree of calcium crosslinking), process variables (pH of pectin, method of crosslinking), and environmental variables on the release of antimicrobial compounds, especially nisin. A secondary objective was to demonstrate the concept that release of active compounds could be altered by varying the degree of calcium crosslinking within the pectin matrix. Antimicrobial compounds such as sodium benzoate, potassium sorbate and nisin were chosen based on their different physical and chemical properties. Coomassie blue dye was used as a model compound for proof of concept. Films were produced from LM pectin by varying the DE of pectin and calcium concentration using the solution casting method. Release of antimicrobial compounds into water as a food simulant was measured by UV/Visible spectrophotometry or HPLC or agar diffusion assay, depending on the antimicrobial compound being evaluated. Degree of calcium crosslinking, pH of pectin slurry and method of calcium crosslinking were identified as the key variables controlling release of nisin from pectin films. Electrostatic attraction between pectin and nisin at pH above pKa of pectin was not sufficiently strong to prevent the release of nisin. Release studies with dye-containing pectin films demonstrated that variable release rates could be obtained by altering the degree of calcium crosslinking.M.S.Includes bibliographical references (p. 73-80)