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Attempts were made to solubilize thymol in Tween 80 micelle to study the solubilization mechanism of thymol and the effect of solubilization on its antioxidant activity. The maximum solubilized concentration of thymol in a 2.0% (w/v) Tween 80 micelle solution is 0.2 wt%. There was no significant difference in Z-average diameter between the empty micelles and thymol solubilized micelles. 1H NMR spectra indicated that 3-H and 4-H on the benzene ring of thymol interacted with the ester group between the hydrophilic head group and the hydrophobic tail group of Tween 80 by Van der Waals’ force. Ferric reducing antioxidant potential (FRAP) and cupric ion reducing antioxidant capacity (CUPRAC) assays showed that the reducing antioxidant activity of free thymol did not change after solubilized in Tween 80 micelles. Compared to free thymol, the solubilized thymol showed higher activities to scavenge DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl radicals. The present study suggested a possible preparation of thymol-carrying micelles with enhanced antioxidant activities that could be applied in food beverages.

Seedless watermelon (Citrullus lanatus Thunb. Mansfeld, cv. Millionaire) fruit were exposed to 10 µL L −1 1-methylcyclopropene (1-MCP) or air for 18 h. Afterward, the fruit were processed into placental-tissue pieces, treated with calcium dips (20 g kg −1 CaCl 2 ) or deionized water, and stored in vented containers for 7 days at 10 • C. At intervals during storage, fresh-cut placental tissue was monitored for respiration, ethylene production, firmness, electrolyte leakage, total soluble solids, titratable acidity and microbial growth. Ethylene production was below detection in fresh-cut placental tissue, consistent with the low ethylene production in intact watermelon fruit. Respiration rates were significantly enhanced in response to tissue processing, and continued to increase throughout the 7 days of storage. Tissue derived from 1-MCP-treated fruit showed enhanced 1-aminocyclopropane-1-carboxylate synthase (ACS, EC 4.4.1.14) activity, suppressed respiratory rates and undetectable levels of 1-aminocyclopropane-1-carboxylate oxidase (ACO) activity during storage. Post-processing calcium dips (CaCl 2 ) had little influence on ACS activity relative to tissue not receiving calcium, but significantly enhanced ACO activity and maintained firmness of fresh-cut tissue throughout storage. The data collectively support the conclusion that 1-methylcyclopropene treatment of intact watermelon fruit is alone unlikely to benefit the storage duration of fresh-cut watermelon.

In this study, chitosan/poly(ethylene oxide) (PEO)/lauric arginate (LAE) composite nanofibrous films were fabricated via electrospinning. The addition of LAE did not change the physical properties of chitosan/PEO in acetic aqueous solutions, but increased the fluorescent intensity of chitosan by electrostatic interactions, resulting in uniform and bead-free nanofibers with an average diameter of 150 nm. The Fourier transform infrared spectra and thermal analysis indicated that the LAE molecules were homogeneously dispersed within the chitosan/PEO nanofibers. The formation of electrostatic and hydrogen bonding interactions induced by the LAE addition changed the inter- and intramolecular interactions between PEO and chitosan and further affected the mobility of the polymer molecules, leading to the increased crystallinity and decreased melting point. The hydrophilicity of the nanofibrous films was significantly increased by the incorporation of LAE, as indicated by the decreasing water contact angle from 39° to 10°. Meanwhile, the chitosan/PEO/LAE nanofibrous films showed LAE concentration dependent antimicrobial activity against Escherichia coli and Staphylococcus aureus, suggesting enhanced antimicrobial activity. The fluorescent staining experiments demonstrated that the antimicrobial mechanism of the nanofibrous films was cell membrane damage.