Chinese research creates edible packaging from soy protein to combat plastic pollution

18 Jul 2023 --- Research from the Chinese University of Hong Kong has created an edible, biodegradable and transparent material using soy protein isolate to replace plastic in food packaging. 

The scientists point to the “pervasive presence” of plastic packaging leading to significant environmental contamination due to excessive reliance on petrochemicals and the inherent non-biodegradability of the material. “The widespread use of petroleum-based plastics as food packaging has created significant pollution to our ecosystem,” write the researchers. 

The material is made from bacterial cellulose (BC) films, which according to the study, present a viable alternative for food packaging applications with their environmentally friendly synthesis process, non-toxic nature, robust mechanical strength and biodegradability. 

However, the bio-based materials’ high hygroscopicity – absorption of moisture in the air, affecting tensile strength – limited their widespread adoption, resulting in diminished strength and barrier properties.

The scientists found they could fix the hygroscopicity by including soy proteins in the material structure of BC and coating the material in an oil-resistant composite to produce an edible film. Therefore, the material can be used in food packaging applications instead of plastic. 

Biodegradable food packaging
The scientists assert their study proposes a novel approach for creating edible, transparent, robust and high-barrier BC-based composite packaging through biosynthesis with the incorporation of soy protein isolate and the physical interpenetration of calcium alginate-polyethylene glycol as a composite coating.

Chinese University Of Hong Kong scientists use soy proteins to increase the durability in a bio-based film for food packaging. The findings demonstrate that the synthesized bio-based composite material exhibits stability in water, high optical transparency, complete oil resistance and full degradability within one to two months. 

Corresponding author and professor at the Chinese University of Hong Kong, To Ngai, told the Society of Chemical Industry: “Extensive research has been conducted on BC, including its use in intelligent packaging, smart films and functionalized materials created through blending, coating and other techniques.”

“These studies demonstrate the potential of BC as a replacement for single-use plastic packaging materials, making it a logical starting point for our research.”

Functionality in tough conditions
The composite material displayed enhanced mechanical properties in dry and wet conditions, with a tensile strength of approximately 84 MPa. The scientists say that these results outperform commercially available kraft paper and low-density PE.

Soy protein isolate established a rigid, coherent and homogeneous network with BCfibrils, augmenting mechanical properties. Calcium alginate can be effectively combined with BC, utilizing PE glycol as a binder and plasticizer, to generate a densely packed structure with reduced hygroscopicity. 

Unlike cellulose found in the cell walls of plants, BC can be produced through microbial fermentation, eliminating the need for harvesting trees or crops. 

The researchers assert that the bio-based composite material demonstrates considerable potential for application in food packaging and other value-added sectors as a substitute for non-degradable plastics.

The study is published in the Wiley Online Library.

By Sabine Waldeck