Abstract
Hexanal and salicylaldehyde are naturally-occurring antimicrobial volatiles from edible plants known for their efficacy for post-harvest preservation of fruits and vegetables. Due to their volatility and susceptibility to oxidation, these volatiles must be encapsulated within a carrier to control their release, especially when applied in modified atmnosphere and active packaging applications. In this study, salicylaldehyde precursor (SP; 1,3-dibenzylethane-2-hydroxyphenyl imidazolidine) and hexanal precursor (HP) were synthetized through a Schiff base reaction between these aldehydes and N,N’-dibenzylethane-1,2-diamine. The structure of SP was confirmed using nuclear magnetic resonance and attenuated total reflection-Fourier transform infrared (FTIR) spectroscopies. SP and HP, separately and in combinations, were encapsulated within ethylcellulose–poly(ethylene oxide) (EC–PEO) nonwoven membranes, using a free-surface electrospinning technique. Scanning electron microscopy showed that the morphology of the fibers varied substantially with SP and HP ratio. Specific interactions between SP and HP with the polymers were not detected from the FTIR spectroscopy analysis, suggesting that the precursors were mainly physically entrapped within the EC–PEO fiber matrix. Headspace gas chromatography showed that the release of hexanal and salicylaldehyde could be activated by contacting the precursor-containing electrospun nonwoven with an acidified agarose gel containing 0.003–0.3 M of citric acid. The delivery system can be promising for controlled release of hexanal and salicylaldehyde to extend the shelf-life of fruits and vegetables.
Highlights
The World and Agriculture Organization estimated that approximately 1.3 billion tonnes of food intended for human consumption is wasted annually, among which, fruits and vegetables account for the greatest wastage [1]
The regeneration of salicylaldehyde can be achieved by acid-catalyzed hydrolysis of the precursor
The molecular structure of the synthesized salicylaldehyde precursor (SP) was confirmed by 1H Nuclear magnetic resonance (NMR) and 13C NMR (Fig. 3a and b, respectively) analyses, showing the presence of the formation of heterocyclic structure, while the benzene rings from substituted diamine and the aromatic hydroxyl group of salicylaldehyde remained unchanged
Summary
The World and Agriculture Organization estimated that approximately 1.3 billion tonnes of food intended for human consumption is wasted annually, among which, fruits and vegetables account for the greatest wastage (nearly 50% of the production) [1]. Deterioration of fruits and vegetables can take place during production, post-harvest, and distribution due to improper handling, thermal abuse, and microbial proliferation, leading to significant losses and potentially causing food-borne diseases [2, 3]. To overcome these issues, cold storage and the use of chemical disinfectants (e.g., chlorine dioxide) are common at the industrial level [4, 5]. Chemical disinfectants are not desirable from environment, public health, and consumer’s perception standpoints [6,7,8]
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