Activated Release of Salicylaldehyde and Hexanal from Branched Polyethylenimine Polymeric Precursor System Encapsulated in Ethyl Cellulose-Poly(ethylene oxide) Nonwovens

To extend the shelf-life of fresh produce, the control of microbial growth and the delay of ripening are important. In this study, naturally occurring volatiles were investigated. Hexanal and salicylaldehyde are potent antimicrobials with hexanal also capable of delaying senescence in plants due to its phospholipase D (PLD) inhibition properties. The current research synthesized branched polyethylenimine (BrPEI)-aldehyde precursors which were substantially more stable than the free aldehydes. The nucleophilic addition of the carbonyl group of the aldehydes to the secondary amines of the BrPEI produced imidazolidine moieties on the polymer chains, which were hydrolysable under mild acidic conditions to release the original aldehydes. The resulting precursors were further dissolved in a spin dope solution comprising of ethyl cellulose/poly(ethylene oxide) (EC/PEO) blend at 100:1 ratio (w/w) in butanol. The polymer solution was electrospun into ultrafine nonwoven membranes using a free surface electrospinning technique. To trigger the release of aldehydes, two different approaches were investigated: (1) direct triggering by adding citric acid solutions (0.1, 0.5 & 1.0 N) to the BrPEI aldehyde precursors encapsulated in EC/PEO electrospun nonwovens; and (2) indirect triggering by humidity/moisture in the air on BrPEI aldehyde precursors encapsulated in EC/PEO electrospun nonwovens containing citric acid monohydrate. To attain a preservation system with salicylaldehyde’s antimicrobial and hexanal’s PLD inhibition properties, a blend precursor was developed that concurrently released both the aldehydes. The polymeric aldehyde precursor systems developed here could be potentially useful in active packaging applications applied to food systems for preservation and shelf life extensions. 2020-08-25