The Chinese Institute of Thermal Sciences has made important progress in the research of green polymer film preservation materials

"People take food as the sky, food safety first", fruit and vegetable preservation is an important part of ensuring food safety, has always attracted the attention
of the public.
The Laboratory of New Materials for Dry Cropping, Institute of South Asia, Chinese Academy of Thermal Sciences, constructed amphiphilic chitosan/carboxymethyl gellan gum/mustard essential oil composite materials by modifying chitosan and gellan gum, and studied the barrier properties, mechanical properties and antibacterial properties of the composite materials, and applied the composite coating liquid to mango preservation, which solved the problems of poor mechanical properties and insufficient antibacterial properties of
single chitosan polymer coating film cling film.
The results showed that the coating treatment of amphiphilic chitosan/carboxymethyl gallan gum composite could prolong the peak respiration period of mango and extend the shelf life of mango by 10 days
.
In addition, it was found that amphiphilic chitosan/carboxymethyl gellan composites with mustard essential oil could delay fruit spoilage and aging, and prevent large changes
in fruit nutrients.

 

At present, there are many methods of fruit storage and preservation, mainly including low temperature storage, modified atmosphere storage, heat treatment sterilization, irradiation storage, ozone treatment and chemical preservative treatment, etc.
, but these preservation methods have high cost, complex technology, difficult to control or toxic residue and other problems
.
A truly green and healthy preservation method has become the expectation of
the entire industry.
Therefore, based on the principle of efficient, safe, environmentally friendly, low cost and easy to operate, film preservation came into being
.
Film preservation is one of the new preservation methods emerging in recent years, which uses the coating liquid to form a thin polymer film on the surface of the fruit to inhibit the gas and water vapor exchange of fruits and vegetables and the metabolism of fruits and vegetables, thereby reducing the respiration intensity of harvesting fruits, reducing water evaporation, and achieving the purpose
of prolonging the shelf life of fruits.

 

Green and efficient coating materials are the key to the development of
film preservatives.
Chitosan is one of the most abundant polysaccharides in nature, with good biocompatibility, degradability, film-forming, barrier and antibacterial, and is considered to be one of the
ideal materials for edible film preservation.
However, chitosan membrane has problems such as
poor mechanical properties and insufficient bacteriostatic performance after filming.
Gellan gum is a natural microbial polysaccharide, with high transparency, wide acid resistance, strong stability, gelling, flavor release, high temperature resistance and other properties, has been widely used in food, daily necessities, pharmaceuticals and other fields, the introduction of gellan gum can effectively improve the mechanical properties
of chitosan after filming.
Plant essential oil is a kind of plant-derived secondary metabolites, with broad-spectrum, efficient antibacterial activity, is recognized as pollution-free natural antiseptic preservative, can not only effectively improve the anti-corrosion and antibacterial effect of the coating material, but also improve the mechanical properties of the coating film, produce synergistic effect
.
In this study, chitosan carboxymethyl was modified and a cholic acid group was introduced to form an amphiphilic chitosan derivative (CMCS-g-CA), which had good water solubility and better compatibility with hydrophobic materials, and then compounded with water-soluble carboxymethyl gellan glue (CMGG) to construct polymer film preservation materials
.
In this work, in order to obtain a composite film with the best mechanical and barrier properties, the suitable weight ratio of CMCS-G-CA/CMGG was determined to be 5:2
by showing the water permeability and mechanical properties of the composite film.
At the same time, the CMCS-G-CA/CMGG/MEO COMPLEX MEMBRANE WITH MUSTARD ESSENTIAL OIL (MEO) HAD GOOD ANTIBACTERIAL PROPERTIES AGAINST Escherichia coli, Staphylococcus aureus and Bacillus anthracis, and the antibacterial activity gradually increased
with the increase of MEO dosage.
Mango coated with CMCS-G-CA/CMGG/MEO had a 10-day extended shelf life at room temperature compared to uncoated mango samples
.
This study shows that chitosan/gellan gum/plant essential oil composites can be applied to the development of food preservation packaging materials with high antibacterial activity, providing a new strategy
for the development of green multifunctional fruit preservation materials.

 

The research results were published in the top international journal Carbohydrate Polymers as "Amphiphilic chitosan/carboxymethyl gellan gum composite films enriched with mustard essential oil for mango preservation
" 。 Associate researcher Yang Ziming of the South Asia Institute of China Academy of Thermal Sciences and Guan Chen, a graduate student of Huazhong Agricultural University, are the co-first authors of the paper, and Professor Li Puwang and Assistant Researcher Zhou Chuang are the co-corresponding authors
of the paper.
This work was supported by the Hainan Provincial Key R&D Program (ZDYF2021XDNY145), the Yunnan Provincial Expert Workstation Project (202005AF150007) and the Basic Scientific Research Business Fund Project of Central Public Welfare Scientific Research Institutes (1630062022006, 1630062022023).

 

Full text link: https://doi.
org/10.
1016/j.
carbpol.
2022.
120290