Existing cleaning methods mainly focus on removing free-state pesticides. However, mancozeb can bind to the wax layer of grapes, forming bound-state residues that are difficult to remove. This study aims to develop an effective cleaning strategy to eliminate both free and bound mancozeb residues from grapes. Compared with the untreated mancozeb aqueous solution, the concentration of free mancozeb significantly decreased ( p < 0.05) after treatment with ozonated water (OW), electrolyzed water (EW), and their combination (OW+EW) for 60 min. The combined treatment synergistically promoted mancozeb degradation, thus reducing its half-life to 38% and 75% of that observed when OW and EW were used alone, respectively. To investigate the effect of the waxy layer on mancozeb removal, oleanolic acid (OLA) was selected as a representative component. The binding effect of OLA limited the degradation of mancozeb in OW and EW, extending its half-life by 1.27 and 1.20 times, respectively. Density functional theory elucidated the mechanism by which the binding of OLA affects the degradation of mancozeb. Interestingly, the decomposition of mancozeb in OW + EW was almost unaffected by the introduction of OLA, indicating that the combined treatment could effectively remove bound-state mancozeb. The combined treatment was then successfully applied to remove mancozeb from grapes. After exposure to OW + EW for 10 min, the removal efficiency of mancozeb reached up to 80.61% with minimal risks of ethylene thiourea formation. There was no obvious change in the surface color of grapes after treatment. The findings provide valuable guidance for removing mancozeb from fresh fruits rich in waxy coatings.
Raw bamboo possesses wax layer, which endows the surface hydrophobic property but makes the anti-fungal chemicals enter difficultly. In this work, lipase was utilized to remove the wax layer from bamboo epidermis for increasing the permeability of raw bamboo. The lipase treatment was optimized as 24 h reaction in buffer solution with a pH value of 8.5 and a temperature of 40 ℃. The weight percentage gain (WPG) of water characterizing the permeability of raw bamboo was used to evaluate the treatment effect. In addition, the bonding strength of bamboo surface was assessed using epoxy resin to further investigate the effect of lipase treatment. Compared with untreated bamboo, WPG increased to 14.7% after 72 h, and the bonding strength improved from 0.01 MPa to 0.73 MPa. The phenomenon could be explained by the diminished contact angle of bamboo epidermis, which decreased from 102.4 °to 73.5 °. An in-depth study on how lipase improves the permeability of bamboo epidermis was investigated using the GC-MS, TG, and DSC analyses. This work provides a green processing method to increase the permeability of bamboo epidermis, which will be beneficial for enhancing the fungal and cracking resistance of raw bamboo through chemical impregnation or modification.
The alteration of surface microstructures and chemical composition in cuticle of papaya fruit in response to chilling stress were comparatively studied between cultivars of ‘Risheng’ and ‘Suihuang’ after harvest. Fruit surface was covered by fissured wax layers in both cultivars. The presence of granule crystalloids was cultivar dependent, with higher abundance in 'Risheng' and lower in 'Suihuang'. Various typical very-long-chain aliphatics i.e., fatty acids, aldehydes, n -alkanes, primary alcohols, and n -alkenes dominated waxes; and cutin monomers were prominently 9/10,16-dihydroxyhexadecanoic acid in papaya fruit cuticle. Chilling pitting symptom was accompanied by modification of granule crystalloids into flat appearance and decreased primary alcohols, fatty acids, and aldehydes in ‘Risheng’, but no evident changes in ‘Suihuang’. The response of cuticle to chilling injury in papaya fruit might be not directly related to the overall amount of waxes and cutin monomers, but more likely to the alteration of appearance morphologies and chemical composition in cuticle.
危险品化学品经营许可证（带存储）