Microencapsulation of hexanal by radiant energy vacuum microwave-molecular inclusion for controlled release and inhibition of Penicillium expansum in a model system and on apple tissue

Abstract

The shelf-life of apple slices is limited due to rapid decay caused by the growth of fungi such as Penicillium expansum. The purpose of this work was to examine the controlled release of hexanal for the inhibition of P. expansum in a model system and on fresh-cut apple. Hexanal was microencapsulated in β-cyclodextrin–pectin blends by radiant energy vacuum (REV) drying and conventional freeze drying. Inhibition of P. expansum was examined by measurement of radial growth on the surface of potato dextrose agar in petri dishes incubated for 5days at 25°C and 10days at 12°C. Apple slices inoculated with P. expansum spores were stored for 15days at 5°C and 12days at 12°C in sealed glass jars. Hexanal release profiles were quantified using solid phase microextraction gas chromatography (SPME-GC). Release of hexanal from the microcapsules delayed P. expansum spore germination and radial growth on PDA at both temperatures. The visual quality of apple slices stored with microencapsulated complexes was improved when compared to a negative control for up to 15days at 5°C, showing a visual quality rating of 5.67–6.00, while the negative control had a rating of 2.00. The growth of P. expansum applied to the flesh was inhibited by the inclusion of microcapsules dried by lyophilization or REV drying. Encapsulation of hexanal in β-cyclodextrin–pectin blends may provide a means to extend the shelf-life of this highly perishable product.