Preservation Mechanism of Chitosan-Based Coating with Cinnamon Oil for Fruits Storage Based on Sensor Data

Abstract

The chitosan-based coating with antimicrobial agent has been developed recently to control the decay of fruits. However, its fresh keeping and antimicrobial mechanism is still not very clear. The preservation mechanism of chitosan coating with cinnamon oil for fruits storage is investigated in this paper. Results in the atomic force microscopy sensor images show that many micropores exist in the chitosan coating film. The roughness of coating film is affected by the concentration of chitosan. The antifungal activity of cinnamon oil should be mainly due to its main consistent trans-cinnamaldehyde, which is proportional to the trans-cinnamaldehyde concentration and improves with increasing the attachment time of oil. The exosmosis ratios of Penicillium citrinum and Aspergillus flavus could be enhanced by increasing the concentration of cinnamon oil. Morphological observation indicates that, compared to the normal cell, the wizened mycelium of A. flavus is observed around the inhibition zone, and the growth of spores is also inhibited. Moreover, the analysis of gas sensors indicate that the chitosan-oil coating could decrease the level of O2 and increase the level of CO2 in the package of cherry fruits, which also control the fruit decay. These results indicate that its preservation mechanism might be partly due to the micropores structure of coating film as a barrier for gas and a carrier for oil, and partly due to the activity of cinnamon oil on the cell disruption.

An Analysis of the Published Literature on the Effects of Edible Coatings Formed by Polysaccharides and Essential Oils on Postharvest Microbial Control and Overall Quality of Fruit

“…Seven studies used medium molecular weight (MW) CH (Aloui et al., ; Athayde et al., ; Barreto et al., ; de Oliveira, Berger, de Araújo, Câmara, & de Souza, ; dos Santos et al., ; Oliveira, de Oliveira, Vieira, Câmara, & de Souza, ; Sun et al., ) and two studies used high MW CH (Cháfer, Sánchez‐González, González‐Martínez, & Chiralt, ; Perdones, Sánchez‐González, Chiralt, & Vargas, ). Eight studies did not cite the MW of tested CH (Azevedo et al., ; de Aquino et al., ; Sánchez‐González et al., ; Shao et al., ; Vu, Hollingsworth, Leroux, Salmieri, & Lacroix, ; Xing et al., ; Xing et al., , ). CH was the only polysaccharide used as an antimicrobial ingredient to formulate the edible coatings in retrieved studies.…”

“…Twenty‐four out of the 30 selected studies used EOs for the formulation of edible coatings, such as the EO from cinnamon (Etemadipoor et al., ; Maqbool et al., ; Xing, Li et al., ; Xing et al., , ), lemongrass (Athayde et al., ; Maqbool et al., ; Oliveira et al., ; Vu et al., ; Yousuf & Srivastava, ), peppermint (de Oliveira et al., ; Guerra et al., , ; Vu et al., ), bergamot (Aloui et al., ; Cháfer et al., ; Sánchez‐González et al., ), oregano (Andrade et al., ; Barreto et al., ; dos Santos et al., ; Rodriguez‐Garcia et al., ; Vu et al., ), rosemary (Andrade et al., ), clove (Shao et al., ), thyme (Bosquez‐Molina et al., ; Cháfer et al., ), tea tree (Cháfer et al., ), Mexican lime (Bosquez‐Molina et al., ), and Lippia gracilis (Azevedo et al., ; de Aquino et al., ). Only five studies used ICs to formulate edible coatings, to cite: carvacrol (de Souza et al., ; Sun et al., ), cinnamaldehyde and trans ‐cinnamaldehyde (Sun et al., ), thymol (Gniewosz & Synowiec, ), citral and eugenol (Guerreiro et al., ), and limonene (Vu et al., ).…”

“…The type and concentration of the polysaccharide as well as of the EO or IC used to formulate the edible coatings used in in situ assays were selected overall considering their antimicrobial effects determined firstly in in vitro assays, as measured through the determination of the minimum inhibitory concentration (MIC; Aloui et al., ; Andrade et al., ; Azevedo et al., ; Bosquez‐Molina et al., ; de Aquino et al., ; de Souza et al., ; dos Santos et al., ; Gniewosz & Synowiec, ; Guerreiro et al., ; Maqbool et al., ; Sun et al., ; Xing et al., ).…”

“…The studies have ordinarily used sub‐MICs of these substances/compounds to formulate the coatings (de Oliveira et al., ; de Souza et al., ; Guerra et al., , ; Oliveira et al., ). Only five studies did not perform in vitro assays to select the concentrations of EOs or ICs used to formulate the coatings (Cháfer et al., ; Etemadipoor et al., ; Perdones et al., ; Xing et al., 2011; Xing et al., ) and two studies used the same concentration in both in vitro and in situ assays (Maqbool et al., ; Rodriguez‐Garcia et al., ), which were selected considering data of previous published studies.…”

“…CH‐coating forming dispersions were usually prepared by dissolving this polymer in an aqueous 0.1 M acetic acid solution under stirring (mostly 150 rpm) for a variable time period, to cite: 1 hr (Xing et al., 2011; Xing et al., , ), 6 hr (Guerra et al., ), 12 hr (Aloui et al., ; Sánchez‐González et al., ), or 24 hr (Athayde et al., ; de Oliveira et al., ; de Souza et al., ; dos Santos et al., ; Oliveira et al., ). Some studies have used an overnight stirring (Cháfer et al., ; Sun et al., ; Vu et al., ) or have not reported the stirring time (Azevedo et al., ; de Aquino et al., ; Perdones et al., ; Shao et al., ).…”