Article pubs.acs.org/JAFC
Novel Solid Encapsulation of Ethylene Gas Using Amorphous α‑Cyclodextrin and the Release Characteristics Binh T. Ho*,†,§ and Bhesh R. Bhandari† †
School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia Department of Food Technology, Faculty of Agriculture & Natural Resources, An Giang University, Long Xuyen, An Giang, Vietnam
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ABSTRACT: This research investigated the encapsulation of ethylene gas into amorphous α-cyclodextrins (α-CDs) at low (LM) and high (HM) moisture contents at 1.0−1.5 MPa for 24−120 h and its controlled release characteristics at 11.2−52.9% relative humidity (RH) for 1−168 h. The inclusion complexes (ICs) were characterized using X-ray diffractometry (XRD), nuclear magnetic resonance spectroscopy (CP-MAS 13C NMR), and scanning electron microscopy (SEM). Ethylene concentrations in the ICs were from 0.45 to 0.87 mol of ethylene/mol CD and from 0.42 to 0.54 mol of ethylene/mol CD for LM and HM α-CDs, respectively. Ethylene gas released from the encapsulated powder at higher rates with increasing RH. An analysis of release kinetics using Avrami’s equation showed that the LM and HM amorphous α-CDs were not associated with significant differences in release constant k and parameter n for any given RH condition. NMR spectra showed the presence of the characteristic carbon−carbon double bond of ethylene gas in the encapsulated α-CD powder. KEYWORDS: amorphous, α-cyclodextrins, encapsulation, ethylene, release
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Ethylene gas (CH2CH2) is a phytohormone that has physiological effects on horticultural products. The gas possesses properties that are potentially beneficial for ripening, degreening, and flowering of a range of fruits.17,18 Ethylene gas, with its hydrophobic characteristics and size (length of CC (132 pm) and CH (108.2 pm)),19 is suitable for inclusion into α-CD molecules. It is commercially available in pressurized cylinders for ripening practices; however, there are drawbacks in handling it, especially for in-transit ripening where safety concerns can be an issue. Ethylene gas encapsulated in a solid state material would potentially be a more practical and safer form for industrial use. For this reason, a detailed study was done of the encapsulation of ethylene gas into α-CD using the liquid encapsulation process at elevated pressures of 0.2−1.5 MPa to produce ethylene−α-CD IC powder.16 In this process, the recovery of crystalline complex powder was
