One-pot preparation of carboxymethyl cellulose-based multifunctional active film embedded with Cu-BTC (benzenetricarboxylic acid) metal-organic framework for mango preservation

Cu-BTC (benzenetricarboxylic acid) is a commercially safe metal-organic framework, but its use in constructing active films is hindered by water instability, uniformity of dispersion and multistep preparation processes. In the study, a carboxymethyl cellulose (CMC)-based multifunctional active film embedded with Cu-BTC was prepared and characterized to preserve mangoes. The small and uniform Cu-BTC crystals (1.25 μm) with water-resistant performance can be produced by adding polyvinylpyrrolidone. The microstructure results showed that this film was innovatively one-step preparation based on CMC matrix, water-resistant Cu-BTC and emulsion system. In the process, Cu-BTC adsorbing cinnamon essential oil (CEO) and liquid paraffin as oil phase was stabilized with CMC aqueous phase by emulsifier Tween 80. Compared with traditional emulsion films (CMC/CEO), this film improved loading capacity of CEO by 4.62 times. The release rates of CEO in the film increased from 17.6 % to 74.8 % with moisture increasing from 10 % to 40 % in ethanol aqueous solutions. Compared with pure CMC film, this film decreased water vapor permeability by approximately 55.0 % and increased water contact angle from 70.6° to 95.6°. In addition, this film possessed applicable water solubility (71.7 %), moderate oxygen permeability and enhanced UV–visible barrier. Cu-BTC and CEO endowed ethylene adsorption properties and antibacterial activity. Furthermore, the film decreased water loss by 23.2 %, increased firmness by 103.1 % and maintained overall quality of fresh mangoes for 12 d at 25 °C. Therefore, the multifunctional Cu-BTC active film was readily produced and is promising to preserve perishable mangoes.