In recent years, polylactic acid (PLA), as a mainstream biodegradable material, has been widely regarded as a replacement for traditional petroleum-based food packaging plastics.
However, pure PLA films inherently have performance limitations, restricting their large-scale application in the packaging of fresh and easily oxidized foods.
A research team at Hassandin University in Indonesia has taken a different approach, using coconut water fermentation to produce cellulose-modified PLA to construct a three-layer composite active packaging film. This effectively improves the film's oxygen barrier properties and mechanical strength, providing a new approach for the development of high-performance biodegradable food packaging.
01. The Inherent Application Limitations of Pure PLA Films Polylactic acid is a biodegradable polyester that can gradually degrade under industrial composting conditions, offering significant environmental advantages. However, unmodified pure PLA has two key drawbacks:
• Weak oxygen barrier properties: Oxygen easily penetrates the film, accelerating food oxidation and spoilage, and shortening shelf life;
• Insufficient mechanical properties: Directly prepared films have limited strength, making it difficult to meet the requirements of industrial packaging production, storage, and transportation.
Previous studies have often focused on adding reinforcing fillers or antioxidants alone to improve performance, rarely achieving the dual functions of enhancement and active oxygen control simultaneously. Balancing preservation ability, mechanical properties, and biodegradability has become a pressing challenge for the industry.
02. Cellulose Filler: An Ideal Reinforcing Material for Modified PLA
Cellulose is a natural polymer filler, offering significant advantages when added to PLA substrates: it can improve tensile strength while reducing oxygen permeability, thus optimizing gas barrier effects.
Conventional modification uses wood and agricultural/forestry crop-derived cellulose to produce microcrystalline cellulose (MCC). However, traditional plant cellulose often contains impurities, leading to uneven dispersion in polymer substrates, causing defects within the film and affecting the stability of the finished product.
03. Unique Advantages of Coconut Water-Based Cellulose
The greatest innovation of this study lies in the cellulose raw material route: relying on coconut water fermentation to produce bacterial cellulose (the production principle is the same as the coconut jelly preparation process).
The fermented bacterial cellulose is purified, hydrolyzed, and pulverized to transform into coconut jelly-based microcrystalline cellulose, which is then used to modify PLA. Compared to commercially available plant-derived microcrystalline cellulose, this material offers significant advantages: Higher purity, free of impurities such as lignin and hemicellulose; finer fiber structure, uniformly dispersed in the PLA matrix; and a more uniform internal structure in the formed film, resulting in fewer defects and better stable oxygen barrier effects.
Soil degradation tests show that the composite film containing this filler achieved a biodegradation rate of 28.86% after 25 days of burial, meeting the basic standards for similar biodegradable polymer materials.
The study also revealed a trend: as the amount of coconut jelly-based microcrystalline cellulose added increases, the film's density and rigidity continuously improve, but the material's brittleness increases and tensile toughness decreases, representing a performance balance that needs further optimization.
04. Three-Layer Composite Film Structure Design with BHT Antioxidant
The research team designed a three-layer PLA composite film structure to achieve integrated structural enhancement and active preservation: All three substrates are based on PLA, blended entirely with coconut jelly-based microcrystalline cellulose, improving overall mechanical properties and basic barrier performance; The two inner layers are additionally compounded with di-tert-butyl-p-cresol (BHT) antioxidant, adhering closely to the food side to absorb oxygen, constructing an "active packaging" system that actively inhibits food oxidation and spoilage.
This layered design achieves functional zoning: the outer layer provides physical protection, while the inner layer carries antioxidant components, overcoming the limitation of ordinary single-layer biodegradable films that only passively block gases.
05. Research Value and Commercialization Challenges
Test results confirm that the coconut jelly-based microcrystalline cellulose-modified three-layer PLA composite film has significantly better oxygen barrier capabilities than pure PLA film, combining biodegradability with active preservation functions.
However, this solution still faces challenges before mass production: the addition of cellulose increases the film's brittleness, making it prone to breakage under external forces and unsuitable for direct adaptation to flexible packaging processes; furthermore, the use of BHT antioxidants in food contact materials requires systematic substance migration safety assessments.
Currently, this film possesses considerable R&D potential but has not yet developed into a mature commercial solution, nor can it completely solve the problem of plastic pollution.
In the long run, this technology opens up a pathway for the high-value utilization of coconut by-products, aligns with the development direction of sustainable packaging, helps achieve sustainable development goals such as responsible consumption and mitigating climate change, and provides a new technological route for reducing plastic in global food packaging.
